SiT5155
±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Description
The SiT5155 is a ±0.5 ppm MEMS Super-TCXO that is
engineered for high reliability, GNSS-based precision
positioning and timing applications.
Leveraging SiTime’s unique DualMEMS™ temperature
sensing and TurboCompensation™ technologies, the
SiT5155 delivers the best dynamic performance for timing
stability in the presence of environmental stressors such as
air flow, temperature perturbation, vibration, shock, and
electromagnetic interference. This device also integrates
multiple on-chip regulators to filter power supply noise,
eliminating the need for a dedicated external LDO.
The SiT5155 offers three device configurations that can be
ordered using Ordering Codes for:
The SiT5155 can be factory programmed for specific
combinations of frequency, voltage, and pull range.
Programmability enables designers to optimize clock
configurations while eliminating long lead times and
customization costs associated with quartz devices where
each frequency is custom built.
Refer to Manufacturing Guideline for proper reflow profile
and PCB cleaning recommendations to ensure best
performance.
Features
◼ 12 frequencies from 10 MHz to 40 MHz
◼ Factory programmable options for short lead time
◼ Best dynamic stability under airflow, thermal shock
▪ ±0.5 ppm stability across temperature
▪ ±15 ppb/°C typical frequency slope (ΔF/ΔT)
◼ -40°C to +105°C operating temperature
◼ No activity dips or micro jumps
◼ Resistant to shock, vibration and board bending
◼ On-chip regulators eliminate the need for external LDOs
◼ Digital frequency pulling (DCTCXO) via I2C
▪ Digital control of output frequency and pull range
▪ Up to ±3200 ppm pull range
▪ Frequency pull resolution down to 5 ppt
◼ 2.5 V, 2.8 V, 3.0 V and 3.3 V supply voltage
◼ LVCMOS or clipped sinewave output
◼ RoHS and REACH compliant
◼ Pb-free, Halogen-free, Antimony-free
Applications
◼ Precision GNSS systems
◼ Microwave backhaul
◼ Professional audio and video equipment
◼ Network routers and switches
◼ Storage and servers
◼ Test and measurement
Block Diagram
Figure 1. SiT5155 Block Diagram
5.0 mm x 3.2 mm Package Pinout
OE / VC / NC 1
2
3
456
7
8
910
SCL / NC
NC
GND
NC
NC
VDD
CLK
A0 / NC
SDA / NC
Figure 2. Pin Assignments (Top view)
(Refer to Table 13 for Pin Descriptions)
Rev 1.04
May 23, 2020
www.sitime.com
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 2 of 38
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Ordering Information
The part number guide illustrated below is for reference only, in which boxes identify order codes having more than one option.
To customize and build an exact part number, use the SiTime Part Number Generator. To validate the part number, use the
SiTime Part Number Decoder.
SiT5155AC - F
K
- 33 E 0 - 10.000000 T
SiT5155AC - F
K
- 33 V T - 10.000000 T
SiT5155AC - F
K
G33 J R - 10.000000 T
Part
Family Silicon
Revision
Letter
Pull Range – DCTCXO mode only
"T": ±6.25 ppm
"R": ±10 ppm
"Q": ±12.5 ppm
"M": ±25 ppm
"B": ±50 ppm
"C": ±80 ppm
"E": ±100 ppm
"F": ±125 ppm
"G": ±150 ppm
"H": ±200 ppm
"X": ±400 ppm
"L": ±600 ppm
"Y": ±800 ppm
"S": ±1200 ppm
"Z": ±1600 ppm
"U": ±3200 ppm
Supply Voltage
"25": 2.5 V ±10%
"28": 2.8 V ±10%
"30": 3.0 V ±10%
"33": 3.3 V ±10%
Frequency
12 GNSS/GPS Frequencies (MHz):
10.000000, 10.949297, 16.367600,
16.367667, 16.368000, 16.369000,
16.384000, 20.000000, 24.553500,
25.000000, 26.000000, 40.000000
Pin 1 Function – DCTCXO mode only
"I": Output Enable
"J": No Connect, software OE control
Temperature Range
"I": Industrial, -40 to 85°C
"C": Extended Commercial, -20 to 70°C
"E": Extended Industrial, -40 to 105°C
TCXO
VCTCXO
DCTCXO
Package Size
"F": 5.0 mm x 3.2 mm Pin 1 Function – TCXO mode only
"E": Output Enable
"N": No Connect
I2C Address Mode – DCTCXO mode only
“0”, “1”, “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9”, “A”, “B”,
“C”, “D”, “E”, “F”: Order code representing hex
value of I2C address. When the I2C address is
factory programmed using this code, pin A0 is no
connect (NC).
“G”: I2C pin addressable mode. Address is set by
the logic on A0 pin.
Packaging
"T": 12 mm Tape & Reel, 3 ku reel
"Y": 12 mm Tape & Reel, 1 ku reel
“X”: 12 mm Tape & Reel, 250 u reel
(blank): bulk[2]
Output Waveform
"-": LVCMOS[1]
"C": Clipped Sinewave
Frequency Stability
"K": for ±0.5 ppm
Notes:
1. “-“ corresponds to the default rise/fall time for LVCMOS output as specified in Table 1 (Electrical Characteristics). Contact SiTime for other rise/fall time
options for best EMI or driving multiple loads. For differential outputs, contact SiTime.
2. Bulk is available for sampling only.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 3 of 38
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TABLE OF CONTENTS
Description ................................................................................................................................................................................... 1
Features ....................................................................................................................................................................................... 1
Applications ................................................................................................................................................................................. 1
Block Diagram ............................................................................................................................................................................. 1
5.0 mm x 3.2 mm Package Pinout ............................................................................................................................................... 1
Ordering Information .................................................................................................................................................................... 2
Electrical Characteristics .............................................................................................................................................................. 4
Device Configurations and Pin-outs ............................................................................................................................................. 9
Pin-out Top Views ................................................................................................................................................................. 9
Test Circuit Diagrams for LVCMOS and Clipped Sinewave Outputs ......................................................................................... 10
Waveforms ................................................................................................................................................................................. 12
Timing Diagrams ........................................................................................................................................................................ 13
Typical Performance Plots ......................................................................................................................................................... 14
Architecture Overview ................................................................................................................................................................ 16
Frequency Stability ............................................................................................................................................................. 16
Output Frequency and Format ............................................................................................................................................ 16
Output Frequency Tuning ................................................................................................................................................... 16
Pin 1 Configuration (OE, VC, or NC) .................................................................................................................................. 17
Device Configurations ................................................................................................................................................................ 17
TCXO Configuration ........................................................................................................................................................... 17
VCTCXO Configuration ...................................................................................................................................................... 18
DCTCXO Configuration ...................................................................................................................................................... 19
VCTCXO-Specific Design Considerations ................................................................................................................................. 20
Linearity .............................................................................................................................................................................. 20
Control Voltage Bandwidth ................................................................................................................................................. 20
FV Characteristic Slope KV ................................................................................................................................................. 20
Pull Range, Absolute Pull Range ........................................................................................................................................ 21
DCTCXO-Specific Design Considerations ................................................................................................................................. 22
Pull Range and Absolute Pull Range .................................................................................................................................. 22
Output Frequency ............................................................................................................................................................... 23
I2C Control Registers .......................................................................................................................................................... 25
Register Descriptions .......................................................................................................................................................... 25
Register Address: 0x00. Digital Frequency Control Least Significant Word (LSW) ............................................................ 25
Register Address: 0x01. OE Control, Digital Frequency Control Most Significant Word (MSW) ......................................... 26
Register Address: 0x02. DIGITAL PULL RANGE CONTROL[15]......................................................................................... 27
Serial Interface Configuration Description .......................................................................................................................... 28
Serial Signal Format ........................................................................................................................................................... 28
Parallel Signal Format ........................................................................................................................................................ 29
Parallel Data Format ........................................................................................................................................................... 29
I2C Timing Specification ...................................................................................................................................................... 31
I2C Device Address Modes ................................................................................................................................................. 32
Schematic Example ............................................................................................................................................................ 33
Dimensions and Patterns ........................................................................................................................................................... 34
Layout Guidelines ...................................................................................................................................................................... 35
Manufacturing Guidelines .......................................................................................................................................................... 35
Additional Information ................................................................................................................................................................ 36
Revision History ......................................................................................................................................................................... 37
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 4 of 38
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Electrical Characteristics
All Min and Max limits are specified over temperature and rated operating voltage with 15 pF output load unless otherwise
stated. Typical values are at 25°C and 3.3 V Vdd.
Table 1. Output Characteristics
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Frequency Coverage
Nominal Output Frequency Range
F_nom
10.000000, 10.949297
16.367600, 16.367667
16.368000, 16.369000
16.384000, 20.000000
24.553500, 25.000000
26.000000, 40.000000
MHz
Temperature Range
Operating Temperature Range
T_use
-20
–
+70
°C
Extended Commercial, ambient temperature
-40
–
+85
°C
Industrial, ambient temperature
-40
–
+105
°C
Extended Industrial, ambient temperature
Frequency Stability
Frequency Stability over
Temperature
F_stab
–
–
±0.5
ppm
Referenced to (max frequency + min frequency)/2 over the
rated temperature range. Vc=Vdd/2 for VCTCXO
Initial Tolerance
F_init
–
–
±1
ppm
Initial frequency at 25°C at 48 hours after 2 reflows
Supply Voltage Sensitivity
F_Vdd
–
±7.10
±16.25
ppb
Vdd ±5%
Output Load Sensitivity
F_load
–
±0.81
±2.75
ppb
LVCMOS output, 15 pF ±10%. Clipped sinewave output,
10 kΩ || 10 pF ±10%
Frequency vs. Temperature Slope
ΔF/ΔT
–
±15
±25
ppb/°C
0.5°C/min temperature ramp rate, -40 to 105°C
Dynamic Frequency Change during
Temperature Ramp
F_dynamic
–
±0.13
±0.21
ppb/s
0.5°C/min temperature ramp rate, -40 to 105°C
One-Year Aging
F_1y
–
±1
–
ppm
At 25°C, after 2-days of continued operation. Aging is
measured with respect to day 3
20-Year Aging
F_20y
–
±2
–
ppm
At 25°C, after 2-days of continued operation. Aging is
measured with respect to day 3
LVCMOS Output Characteristics
Duty Cycle
DC
45
–
55
%
Rise/Fall Time
Tr, Tf
0.8
1.2
1.9
ns
10% - 90% Vdd
Output Voltage High
VOH
90%
–
–
Vdd
IOH = +3 mA
Output Voltage Low
VOL
–
–
10%
Vdd
IOL = -3 mA
Output Impedance
Z_out_c
–
17
–
Ohms
Impedance looking into output buffer, Vdd = 3.3 V
–
17
–
Ohms
Impedance looking into output buffer, Vdd = 3.0 V
–
18
–
Ohms
Impedance looking into output buffer, Vdd = 2.8 V
–
19
–
Ohms
Impedance looking into output buffer, Vdd = 2.5 V
Clipped Sinewave Output Characteristics
Output Voltage Swing
V_out
0.8
–
1.2
V
Clipped sinewave output, 10 kΩ || 10 pF ±10%
Rise/Fall Time
Tr, Tf
–
3.5
4.6
ns
20% - 80% Vdd, F_nom = 20 MHz
Start-up Characteristics
Start-up Time
T_start
–
2.5
3.5
ms
Time to first pulse, measured from the time Vdd reaches
90% of its final value. Vdd ramp time = 100 µs from 0V to
Vdd
Output Enable Time
T_oe
–
–
680
ns
See Timing Diagrams section below
Time to Rated Frequency Stability
T_stability
–
5
45
ms
Time to first accurate pulse within rated stability, measured
from the time Vdd reaches 90% of its final value. Vdd
ramp time = 100 µs
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 5 of 38
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Table 2. DC Characteristics
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Supply Voltage
Supply Voltage
Vdd
2.25
2.5
2.75
V
Contact SiTime for 2.25 V to 3.63 V continuous supply
voltage support
2.52
2.8
3.08
V
2.7
3.0
3.3
V
2.97
3.3
3.63
V
Current Consumption
Current Consumption
Idd
–
44
53
mA
F_nom = 20 MHz, No Load, TCXO and DCTCXO modes
–
48
57
mA
F_nom = 20 MHz, No Load, VCTCXO mode
OE Disable Current
I_od
–
43
51
mA
OE = GND, output weakly pulled down. TCXO, DCTCXO
–
47
55
mA
OE = GND, output weakly pulled down. VCTCXO mode
Table 3. Input Characteristics
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Input Characteristics – OE Pin
Input Impedance
Z_in
75
–
–
kΩ
Internal pull up to Vdd
Input High Voltage
VIH
70%
–
–
Vdd
Input Low Voltage
VIL
–
–
30%
Vdd
Frequency Tuning Range – Voltage Control or I2C mode
Pull Range
PR
±6.25
–
–
ppm
VCTCXO mode; contact SiTime for ±12.5 and ±25 ppm
±6.25
±10
±12.5
±25
±50
±80
±100
±125
±150
±200
±400
±600
±800
±1200
±1600
±3200
–
–
ppm
DCTCXO mode
Absolute Pull Range[3]
APR
±2.75
–
–
ppm
DCTCXO, VCTCXO for PR = ±6.25 ppm
Upper Control Voltage
VC_U
90%
–
–
Vdd
VCTCXO mode
Lower Control Voltage
VC_L
–
–
10%
Vdd
VCTCXO mode
Control Voltage Input Impedance
VC_z
8
–
–
MΩ
VCTCXO mode
Control Voltage Input Bandwidth
VC_bw
–
10
–
kHz
VCTCXO mode; contact SiTime for other bandwidth options
Frequency Control Polarity
F_pol
Positive
VCTCXO mode
Pull Range Linearity
PR_lin
–
0.5
1.0
%
VCTCXO mode
I2C Interface Characteristics, 200 Ohm, 550 pF (Max I2C Bus Load)
Bus Speed
F_I2C
≤ 400
kHz
-40 to 105°C
≤ 1000
kHz
-40 to 85°C
Input Voltage Low
VIL_I2C
–
–
30%
Vdd
DCTCXO mode
Input Voltage High
VIH_I2C
70%
–
–
Vdd
DCTCXO mode
Output Voltage Low
VOL_I2C
–
–
0.4
V
DCTCXO mode
Input Leakage current
IL
0.5
–
24
µA
0.1 VDD< VOUT < 0.9 VDD. Includes typical leakage current
from 200 kΩ pull resister to VDD. DCTCXO mode
Input Capacitance
CIN
–
–
5
pF
DCTCXO mode
Note:
3. APR = PR – initial tolerance – 20-year aging – frequency stability over temperature. Refer to Table 17 for APR with respect to other pull range options.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 6 of 38
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Table 4. Jitter & Phase Noise – LVCMOS, -40°C to 85°C
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Jitter
RMS Phase Jitter (random)
T_phj
–
0.31
0.48
ps
F_nom = 10 MHz, Integration bandwidth = 12 kHz to 5 MHz
RMS Period Jitter
T_jitt_per
–
0.8
1.1
ps
F_nom = 10 MHz, population 10 k
Peak Cycle-to-Cycle Jitter
T_jitt_cc
–
6
9
ps
F_nom = 10 MHz, population 1 k, measured as absolute
value
Phase Noise
1 Hz offset
–
-80
-74
dBc/Hz
F_nom = 10 MHz
TCXO and DCTCXO modes, and VCTCXO mode with
±6.25 ppm pull range
10 Hz offset
–
-108
-102
dBc/Hz
100 Hz offset
–
-127
-123
dBc/Hz
1 kHz offset
–
-148
-145
dBc/Hz
10 kHz offset
–
-154
-151
dBc/Hz
100 kHz offset
–
-154
-150
dBc/Hz
1 MHz offset
–
-167
-163
dBc/Hz
5 MHz offset
–
-168
-164
dBc/Hz
Spurious
T_spur
–
-112
-105
dBc
F_nom = 10 MHz, 1 kHz to 5 MHz offsets
Table 5. Jitter & Phase Noise – Clipped Sinewave, -40°C to 85°C
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Jitter
RMS Phase Jitter (random)
T_phj
–
0.31
0.45
ps
F_nom = 20 MHz, Integration bandwidth = 12 kHz to 5 MHz
Phase Noise
1 Hz offset
–
-74
-68
dBc/Hz
F_nom = 20 MHz
TCXO and DCTCXO modes, and VCTCXO mode with
±6.25 ppm pull range
10 Hz offset
–
-102
-97
dBc/Hz
100 Hz offset
–
-121
-117
dBc/Hz
1 kHz offset
–
-142
-140
dBc/Hz
10 kHz offset
–
-148
-146
dBc/Hz
100 kHz offset
–
-149
-145
dBc/Hz
1 MHz offset
–
-162
-159
dBc/Hz
5 MHz offset
–
-164
-160
dBc/Hz
Spurious
T_spur
–
-109
-104
dBc
F_nom = 20 MHz, 1 kHz to 5 MHz offsets
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 7 of 38
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Table 6. Jitter & Phase Noise – LVCMOS, -40°C to 105°C
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Jitter
RMS Phase Jitter (random)
T_phj
–
0.31
0.48
ps
F_nom = 10 MHz, Integration bandwidth = 12 kHz to 5 MHz
RMS Period Jitter
T_jitt_per
–
0.8
1.1
ps
F_nom = 10 MHz, population 10 k
Peak Cycle-to-Cycle Jitter
T_jitt_cc
–
6
9
ps
F_nom = 10 MHz, population 1 k, measured as absolute
value
Phase Noise
1 Hz offset
–
-80
-74
dBc/Hz
F_nom = 10 MHz
TCXO and DCTCXO modes, and VCTCXO mode with
±6.25 ppm pull range
10 Hz offset
–
-108
-102
dBc/Hz
100 Hz offset
–
-127
-123
dBc/Hz
1 kHz offset
–
-148
-145
dBc/Hz
10 kHz offset
–
-154
-151
dBc/Hz
100 kHz offset
–
-154
-150
dBc/Hz
1 MHz offset
–
-167
-162
dBc/Hz
5 MHz offset
–
-168
-163
dBc/Hz
Spurious
T_spur
–
-112
-101
dBc
F_nom = 10 MHz, 1 kHz to 5 MHz offsets, Vdd = 2.5 V
–
-112
-106
dBc
F_nom = 10 MHz, 1 kHz to 5 MHz offsets, Vdd = 2.8 V,
3.0 V, 3.3 V
Table 7. Jitter & Phase Noise – Clipped Sinewave, -40°C to 105°C
Parameters
Symbol
Min.
Typ.
Max.
Unit
Condition
Jitter
RMS Phase Jitter (random)
T_phj
–
0.31
0.46
ps
F_nom = 20 MHz, Integration bandwidth = 12 kHz to 5 MHz
Phase Noise
1 Hz offset
–
-74
-68
dBc/Hz
F_nom = 20 MHz
TCXO and DCTCXO modes, and VCTCXO mode with
±6.25 ppm pull range
10 Hz offset
–
-102
-97
dBc/Hz
100 Hz offset
–
-121
-117
dBc/Hz
1 kHz offset
–
-142
-140
dBc/Hz
10 kHz offset
–
-148
-146
dBc/Hz
100 kHz offset
–
-149
-145
dBc/Hz
1 MHz offset
–
-162
-158
dBc/Hz
5 MHz offset
–
-164
-159
dBc/Hz
Spurious
T_spur
–
-109
-103
dBc
F_nom = 20 MHz, 1 kHz to 5 MHz offsets
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 8 of 38
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Table 8. Absolute Maximum Limits
Attempted operation outside the absolute maximum ratings may cause permanent damage to the part.
Actual performance of the IC is only guaranteed within the operational specifications, not at absolute maximum ratings.
Parameter
Test Conditions
Value
Unit
Storage Temperature
-65 to 125
°C
Continuous Power Supply Voltage Range (Vdd)
-0.5 to 4
V
Human Body Model (HBM) ESD Protection
JESD22-A114
2000
V
Soldering Temperature (follow standard Pb-free soldering guidelines)
260
°C
Junction Temperature[4]
130
°C
Input Voltage, Maximum
Any input pin
Vdd + 0.3
V
Input Voltage, Minimum
Any input pin
-0.3
V
Note:
4. Exceeding this temperature for an extended period of time may damage the device.
Table 9. Thermal Considerations[5]
Package
JA[6] (°C/W)
JC, Bottom (°C/W)
Ceramic 5.0 mm x 3.2 mm
54
15
Note:
5. Measured in still air. Refer to JESD51 for θJA and θJC definitions.
6. Devices soldered on a JESD51 2s2p compliant board.
Table 10. Maximum Operating Junction Temperature[7]
Max Operating Temperature (ambient)
Maximum Operating Junction Temperature
70°C
80°C
85°C
95°C
105°C
115°C
Note:
7. Datasheet specifications are not guaranteed if junction temperature exceeds the maximum operating junction temperature.
Table 11. Environmental Compliance
Parameter
Test Conditions
Value
Unit
Mechanical Shock Resistance
MIL-STD-883F, Method 2002
30000
g
Mechanical Vibration Resistance
MIL-STD-883F, Method 2007
70
g
Temperature Cycle
JESD22, Method A104
–
–
Solderability
MIL-STD-883F, Method 2003
–
–
Moisture Sensitivity Level
MSL1 @260°C
–
–
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 9 of 38
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Device Configurations and Pin-outs
Table 12. Device Configurations
Configuration
Pin 1
Pin 5
I2C Programmable Parameters
TCXO
OE/NC
NC
–
VCTCXO
VC
NC
–
DCTCXO
OE/NC
A0/NC
Frequency Pull Range, Frequency Pull Value, Output Enable control.
Pin-out Top Views
OE/NC 1
2
3
456
7
8
910
NC
NC
GND
NC
NC
VDD
CLK
NC
NC
Figure 3. TCXO
VC 1
2
3
456
7
8
910
NC
NC
GND
NC
NC
VDD
CLK
NC
NC
Figure 4. VCTCXO
OE / NC 1
2
3
456
7
8
910
SCL
NC
GND
NC
NC
VDD
CLK
A0 / NC
SDA
Figure 5. DCTCXO
Table 13. Pin Description
Pin
Symbol
I/O
Internal Pull-up/Pull Down
Resistor
Function
1
OE/NC[10]/VC
OE – Input
100 kΩ Pull-Up
H[8]: specified frequency output
L: output is high impedance. Only output driver is disabled.
NC – No Connect
–
H or L or Open: No effect on output frequency or other device functions
VC – Input
–
Control Voltage in VCTCXO Mode
2
SCL/NC[10]
SCL – Input
200 kΩ Pull-Up
I2C serial clock input.
No Connect
H or L or Open: No effect on output frequency or other device functions
3
NC[10]
No Connect
–
H or L or Open: No effect on output frequency or other device functions
4
GND
Power
–
Connect to ground
5
A0/NC[10]
A0 – Input
100 kΩ Pull-Up
Device I2C address when the address selection mode is via the A0 pin.
This pin is NC when the I2C device address is specified in the ordering
code.
A0 Logic Level I2C Address
0 1100010
1 1101010
NC – No Connect
–
H or L or Open: No effect on output frequency or other device functions.
6
CLK
Output
–
LVCMOS, or clipped sinewave oscillator output
7
NC[10]
No Connect
–
H or L or Open: No effect on output frequency or other device functions
8
NC[10]
No Connect
–
H or L or Open: No effect on output frequency or other device functions
9
VDD
Power
–
Connect to power supply[9]
10
SDA/NC[10]
SDA – Input/Output
200 kΩ Pull Up
I2C Serial Data.
NC – No Connect
–
H or L or Open: No effect on output frequency or other device functions.
Notes:
8. In OE mode for noisy environments, a pull-up resistor of 10 kΩ or less is recommended if pin 1 is not externally driven. If pin 1 needs to be left floating, use
the NC option.
9. A 0.1 μF capacitor in parallel with a 10 μF capacitor are required between VDD and GND. The 0.1 μF capacitor is recommended to place close to the
device, and place the 10 μF capacitor less than 2 inches away.
10. All NC pins can be left floating and do not need to be soldered down.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 10 of 38
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Test Circuit Diagrams for LVCMOS and Clipped Sinewave Outputs
9 8 7 6
1 2 3 4
510
Power
Supply
VDD Test Point
Vdd
OE Function
CLK
15pF
(including probe
and fixture
capacitance)
10µF
0.1µF
+
-
10µF
0.1µF 9 8 7 6
1 2 3 4
510
Power
Supply
VDD CLK Test Point
Vdd
OE Function
10kΩ
(including probe
and fixture
resistance and
capacitance)
10pF
+
-
Figure 6. LVCMOS Test Circuit (OE Function)
Figure 7. Clipped Sinewave Test Circuit (OE Function)
for AC and DC Measurements
10µF
0.1µF
+
-
9 8 7 6
1 2 3 4
510
Power
Supply
VDD Test Point
Control
Voltage
VC Function
CLK
15pF
(including probe
and fixture
capacitance)
Figure 8. LVCMOS Test Circuit (VC Function)
9 8 7 6
2 3 4
510
Power
Supply
VDD CLK Test Point
1
Control
Voltage
VC Function
10kΩ
(including probe
and fixture
resistance and
capacitance)
10pF
10µF
0.1µF
+
-
Figure 9. Clipped Sinewave Test Circuit (VC Function)
for AC and DC Measurements
9 8 7 6
1 2 3 4
510
Power
Supply
VDD Test Point
Any state
or floating
NC Function
CLK
15pF
(including probe
and fixture
capacitance)
10µF
0.1µF
+
-
Figure 10. LVCMOS Test Circuit (NC Function)
9 8 7 6
2 3 4
510
Power
Supply
VDD CLK Test Point
10pF
1
Any state
or floating
NC Function
10kΩ
(including probe
and fixture
resistance and
capacitance)
10µF
0.1µF
+
-
Figure 11. Clipped Sinewave Test Circuit (NC Function)
for AC and DC Measurements
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 11 of 38
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Test Circuit Diagrams for LVCMOS and Clipped Sinewave Outputs (continued)
9 8 7 6
1 2 3 4
510
Power
Supply
VDD Test Point
Any state
or floating NC
Function
CLK
SCL
SDA[11]
15pF
(including probe
and fixture
capacitance)
10µF
0.1µF
+
-
A0/NC
Figure 12. LVCMOS Test Circuit (I2C Control), DCTCXO mode for AC and DC Measurements
9 8 7 6
1 2 3 4
510
Power
Supply
VDD Test Point
Any state
or floating NC
Function
CLK
SCL
SDA[11]
10pF 10kΩ
(including probe
and fixture
resistance and
capacitance)
10µF
0.1µF
+
-
A0/NC
Figure 13. Clipped Sinewave Test Circuit (I2C Control), DCTCXO mode for AC and DC Measurements
9 8 7 6
2 3 4
510
Power
Supply
VDD CLK
10pF
1
Any state
or floating
NC Function
10kΩ
(including probe
and fixture
resistance and
capacitance)
10µF
0.1µF
+
-
Test Point
A0/NC
Figure 14. Clipped Sinewave Test Circuit for Phase Noise Measurements, Applies to All Configurations
(NC Function shown for example only)
Note:
11. SDA is open-drain and may require pull-up resistor if not present in I2C test setup.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 12 of 38
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Waveforms
90 % Vdd
50 % Vdd
10 % Vdd
tr tf
High Pulse
(TH) Low Pulse
(TL)
Period
Figure 15. LVCMOS Waveform Diagram[12]
tr tf
High Pulse
(TH) Low Pulse
(TL)
Period
20 % Vout
50 % Vout
80 % Vout
Vout
Figure 16. Clipped Sinewave Waveform Diagram[12]
Note:
12. Duty Cycle is computed as Duty Cycle = TH/Period.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 13 of 38
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Timing Diagrams
90% Vdd Vdd
Vdd Pin
Voltage
CLK Output
T_start
T_start: Time to start from power-off
HZ
Figure 17. Startup Timing
50% Vdd
Vdd
OE Voltage
CLK Output
T_oe
T_oe: Time to re-enable the clock output
HZ
Figure 18. OE Enable Timing (OE Mode Only)
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 14 of 38
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Typical Performance Plots
Figure 19. Duty Cycle (LVCMOS)
Figure 20. Rise Time (LVCMOS)
Figure 21. IDD TCXO (LVCMOS)
Figure 22. IDD VCTCXO (LVCMOS)
Figure 23. RMS Phase Jitter, TCXO & DCTCXO (LVCMOS)
Figure 24. RMS Period Jitter (LVCMOS)
Figure 25. IDD DCTCXO (LVCMOS)
Figure 26. RMS Phase Jitter, VCTCXO (LVCMOS)
45
47
49
51
53
55
10 15 20 25 30 35 40
Duty cycle (%)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0,90
0,95
1,00
1,05
1,10
1,15
1,20
1,25
10 15 20 25 30 35 40
Rise time (ns)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
40
41
42
43
44
45
46
47
48
10 15 20 25 30 35 40
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
44
45
46
47
48
49
50
51
52
10 20 30 40 50 60
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0
100
200
300
400
500
10 15 20 25 30 35 40
Phase Jitter (fs RMS)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0,50
0,70
0,90
1,10
1,30
1,50
1,70
1,90
10 15 20 25 30 35 40
Period Jitter (ps RMS)
Frequency (MHz)
2.5 V 3.3 V
40
41
42
43
44
45
46
47
48
10 15 20 25 30 35 40
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0
100
200
300
400
500
10 15 20 25 30 35 40
Phase Jitter (fs RMS)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 15 of 38
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Typical Performance Plots (continued)
Figure 27. DCTCXO frequency pull characteristic
Figure 28. Rise Time (Clipped Sinewave)
Figure 29. IDD TCXO (Clipped Sinewave)
Figure 30. IDD VCTCXO (Clipped Sinewave)
Figure 31. RMS Phase Jitter, TCXO & DCTCXO (Clip Sine)
Figure 32. IDD DCTCXO (Clipped Sinewave)
Figure 33. RMS Phase Jitter, VCTCXO (Clipped Sine)
Figure 34. Duty Cycle (Clipped Sinewave)
-6,25
-5
-3,75
-2,5
-1,25
0
1,25
2,5
3,75
5
6,25
-6,25 -5 -3,75 -2,5 -1,25 0 1,25 2,5 3,75 5 6,25
Frequency deviation (ppm)
DCTCXO pull (ppm)
2,80
3,00
3,20
3,40
3,60
3,80
4,00
4,20
4,40
4,60
10 15 20 25 30 35 40
Rise Time (ns)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
43,0
43,5
44,0
44,5
45,0
45,5
10 15 20 25 30 35 40
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
43
44
45
46
47
48
49
50
10 15 20 25 30 35 40
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0
100
200
300
400
500
10 15 20 25 30 35 40
Phase Jitter (fs RMS)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
43,0
43,5
44,0
44,5
45,0
45,5
46,0
46,5
10 15 20 25 30 35 40
Current consumption (mA)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
0
100
200
300
400
500
10 15 20 25 30 35 40
Phase jitter (fs RMS)
Frequency (NHz)
2.5 V 2.8 V 3.0 V 3.3 V
45
47
49
51
53
55
10 15 20 25 30 35 40
Duty cycle (%)
Frequency (MHz)
2.5 V 2.8 V 3.0 V 3.3 V
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 16 of 38
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Architecture Overview
Based on SiTime’s innovative Elite Platform™, the SiT5155
delivers exceptional dynamic performance, i.e. resilience to
environmental stressors such as shock, vibration, and fast
temperature transients. Underpinning the Elite platform are
SiTime’s unique DualMEMS™ temperature sensing
architecture and TurboCompensation™ technologies.
DualMEMS is a noiseless temperature compensation
scheme. It consists of two MEMS resonators fabricated on
the same die substrate. The TempFlat™ MEMS resonator
is designed with a flat frequency characteristic over
temperature whereas the temperature sensing resonator is
by design sensitive to temperature changes. The ratio of
frequencies between these two resonators provides an
accurate reading of the resonator temperature with 20 µK
resolution.
By placing the two MEMS resonators on the same die, this
temperature sensing scheme eliminates any thermal lag
and gradients between resonator and temperature sensor,
thereby overcoming an inherent weakness of legacy quartz
TCXOs.
The DualMEMS temperature sensor drives a state-of-the-
art CMOS temperature compensation circuit. The
TurboCompensation design, with >100 Hz compensation
bandwidth, achieves a dynamic frequency stability that is
far superior to any quartz TCXO. The digital temperature
compensation enables additional optimization of
frequency stability and frequency slope over temperature
within any chosen temperature range for a given system
design.
The Elite platform also incorporates a high resolution, low
noise frequency synthesizer along with the industry
standard I2C bus. This unique combination enables system
designers to digitally control the output frequency in steps
as low as 5 ppt and over a wide range up to ±3200 ppm.
For more information regarding the Elite platform and its
benefits please visit:
◼ SiTime's breakthroughs section
◼ TechPaper: DualMEMS Temperature Sensing Technology
◼ TechPaper: DualMEMS Resonator TDC
Functional Overview
The SiT5155 is designed for flexibility with a variety of
factory programmable options, enabling system designers
to configure this precision device for optimal performance
in GNSS/GPS applications.
Frequency Stability
The SiT5155 comes in one factory-trimmed stability
grade.
Table 14. Stability Grades vs. Ordering Codes
Frequency Stability Over Temperature
Ordering Code
±0.5 ppm
K
Output Frequency and Format
The SiT5155 is available in a variety of pre-determined
frequencies for both LVCMOS and clipped sinewave output.
Ordering codes for the output format are shown below:
Table 15. Output Formats vs. Ordering Codes
Output Format
Ordering Code
LVCMOS
“-“
Clipped Sinewave
“C”
Output Frequency Tuning
In addition to the non-pullable TCXO, the SiT5155 can also
support output frequency tuning through either an analog
control voltage (VCTCXO), or I2C interface (DCTCXO). The
I2C interface enables 16 factory programmed pull-range
options from ±6.25 ppm to ±3200 ppm. The pull range can
also be reprogrammed via I2C to any supported pull-range
value.
Refer to Device Configuration section for details.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Pin 1 Configuration (OE, VC, or NC)
Pin 1 of the SiT5155 can be factory programmed to support
three modes: Output Enable (OE), Voltage Control (VC), or
No Connect (NC).
Table 16. Pin Configuration Options
Pin 1 Configuration
Operating Mode
Output
OE
TCXO/DCTCXO
Active or High-Z
NC
TCXO/DCTCXO
Active
VC
VCTCXO
Active
When pin 1 is configured as OE pin, the device output is
guaranteed to operate in one of the following two states:
◼ Clock output with the frequency specified in the part
number when Pin 1 is pulled to logic high
◼ Hi-Z mode with weak pull down when pin 1 is pulled to
logic low.
When pin 1 is configured as NC, the device is guaranteed to
output the frequency specified in the part number at all times,
regardless of the logic level on pin 1.
In the VCTCXO configuration, the user can fine-tune the
output frequency from the nominal frequency specified in the
part number by varying the pin 1 voltage. The guaranteed
allowable variation of the output frequency is specified as pull
range. A VCTCXO part number must contain a valid pull-
range ordering code.
Device Configurations
The SiT5155 supports 3 device configurations – TCXO,
VCTCXO, and DCTCXO. The TCXO and VCTCXO options
are directly compatible with the quartz TCXO and
VCTCXO. The DCTCXO configuration provides
performance enhancement by eliminating VCTCXO’s
sensitivity to control voltage noise with an I2C digital
interface for frequency tuning.
Figure 35. Block Diagram – TCXO
TCXO Configuration
The TCXO generates a fixed frequency output, as shown in
Figure 35. The frequency is specified by the user in the
frequency field of the device ordering code and then factory
programmed. Other factory programmable options include
supply voltage, output types (LVCMOS or clipped
sinewave), and pin 1 functionality (OE or NC).
Refer to the Ordering Information section at the end of the
datasheet for a list of all ordering options.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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VCTCXO Configuration
A VCTCXO, shown in Figure 36, is a frequency control device
whose output frequency is an approximately linear function of
control voltage applied to the voltage control pin. VCTCXOs
have a number of use cases including the VCO portion of a
jitter attenuation/jitter cleaner PLL Loop.
The SiT5155 achieves a 10x better pull range linearity of
<0.5% via a high-resolution fractional PLL and low-noise
precision analog-to-digital converter. By contrast, quartz-based
VCTCXOs change output frequency by varying the capacitive
load of a crystal resonator using varactor diodes, which results
in linearity of 5% to 105%.
Figure 36. Block Diagram – VCTCXO
Note that the output frequency of the VCTCXO is
proportional to the analog control voltage applied to
pin 1. Because this control signal is analog and directly
controls the output frequency, care must be taken to
minimize noise on this pin.
The nominal output frequency is factory programmed
per the customer’s request to 6 digits of precision and
is defined as the output frequency when the control
voltage equals Vdd/2. The maximum output frequency
variation from this nominal value is set by the pull
range, which is also factory programmed to the
customer’s desired value and specified by the ordering
code. The Ordering Information section shows all
ordering options and associated ordering codes.
Refer to VCTCXO-Specific Design Considerations for
more information on critical VCTCXO parameters
including pull range linearity, absolute pull range,
control voltage bandwidth, and KV.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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DCTCXO Configuration
The SiT5155 offers digital control of the output frequency,
as shown in Figure 37. The output frequency is controlled
by writing frequency control words over the I2C interface.
There are several advantages of DCTCXOs relative to
VCTCXOs:
Figure 37. Block Diagram
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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VCTCXO-Specific Design Considerations
Linearity
In any VCTCXO, there will be some deviation of the
frequency-voltage (FV) characteristic from an ideal straight
line. Linearity is the ratio of this maximum deviation to the
total pull range, expressed as a percentage. Figure 38
below shows the typical pull linearity of a SiTime VCTCXO.
The linearity is excellent (1% maximum) relative to most
quartz offerings because the frequency pulling is achieved
with a PLL rather than varactor diodes.
Input Voltage Range
FREQEUNCY
INPUT VOLTAGE
Best Straight
Line Fit
TOTAL PULL RANGE
Figure 38. Typical SiTime VCTCXO Linearity
Control Voltage Bandwidth
Control voltage bandwidth, sometimes called “modulation
rate” or “modulation bandwidth”, indicates how fast a VCO
can respond to voltage changes at its input. The ratio of the
output frequency variation to the input voltage variation,
previously denoted by KV, has a low-pass characteristic in
most VCTCXOs. The control voltage bandwidth equals the
modulating frequency where the output frequency deviation
equals 0.707 (e.g. -3 dB) of its DC value, for DC inputs
swept in the same voltage range.
For example, a part with a ±6.25 ppm pull range and a 0-3V
control voltage can be regarded as having an average KV
of 4.17 ppm/V (12.5 ppm/3 V = 4.17 ppm/V). Applying an
input of 1.5 V DC ± 0.5 V (1.0 V to 2.0 V) causes an output
frequency change of 4.17 ppm (±2.08 ppm). If the control
voltage bandwidth is specified as 10 kHz, the peak-to-peak
value of the output frequency change will be reduced to
4.33 ppm/√2 or 2.95 ppm, as the frequency of the control
voltage change is increased to 10 kHz.
FV Characteristic Slope KV
The slope of the FV characteristic is a critical design
parameter in many low bandwidth PLL applications. The
slope is the derivative of the FV characteristic – the
deviation of frequency divided by the control voltage change
needed to produce that frequency deviation, over a small
voltage span, as shown below:
in
out
VV
f
K
=
It is typically expressed in kHz/Volt, MHz/Volt, ppm/Volt, or
similar units. This slope is usually called “KV” based on
terminology used in PLL designs.
The extreme linear characteristic of the SiTime SiT5155
VCTCXO family means that there is very little KV variation
across the whole input voltage range (typically <1%),
significantly reducing the design burden on the PLL
designer. Figure 39 below illustrates the typical KV variation.
Input Voltage Range
KV
INPUT VOLTAGE
KV varies <1% over input
voltage range
Average
Kv
Figure 39. Typical SiTime KV Variation
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Pull Range, Absolute Pull Range
Pull range (PR) is the amount of frequency deviation that
will result from changing the control voltage over its
maximum range under nominal conditions.
Absolute pull range (APR) is the guaranteed controllable
frequency range over all environmental and aging
conditions. Effectively, it is the amount of pull range
remaining after taking into account frequency stability,
tolerances over variables such as temperature, power
supply voltage, and aging, i.e.:
agingstability FFPRAPR −−=
where
stability
F
is the device frequency stability due to initial
tolerance and variations on temperature, power supply, and
load.
Figure 40 shows a typical SiTime VCTCXO FV
characteristic. The FV characteristic varies with
conditions, so that the frequency output at a given input
voltage can vary by as much as the specified frequency
stability of the VCTCXO. For such VCTCXOs, the
frequency stability and APR are independent of each
other. This allows very wide range of pull options without
compromising frequency stability.
Input Voltage Range
FREQUENCY STABILITY
(Temp, Voltage, Aging, etc)
TOTAL PULL RANGE
FREQUENCY
APR
VC_UVC_L
Figure 40. Typical SiTime VCTCXO FV Characteristic
The upper and lower control voltages are the specified
limits of the input voltage range as shown in
Figure 40 above. Applying voltages beyond the upper
and lower voltages do not result in noticeable changes of
output frequency. In other words, the FV characteristic of
the VCTCXO saturates beyond these voltages. Figures 1
and 2 show these voltages as Lower Control Voltage
(VC_L) and Upper Control Voltage (VC_U).
Table 17 below shows the pull range and corresponding
APR values for each of the frequency vs. temperature
ordering options.
Table 17. VCTCXO Pull Range, APR Options[13]
Typical unless specified otherwise. Pull range (PR) is ±6.25 ppm.
Pull Range
Ordering Code
Device Option(s)
APR ppm
±0.5 ppm option
±2 ppm 20-year aging
T
VCTCXO
±2.75
Notes:
13. APR includes initial tolerance, frequency stability vs. temperature, and the corresponding 20-year aging.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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DCTCXO-Specific Design Considerations
Pull Range and Absolute Pull Range
Pull range and absolute pull range are described in the
previous section. Table 18 below shows the pull range and
corresponding APR values for each of the frequency vs.
temperature ordering options.
Table 18. APR Options[14]
Pull Range
Ordering Code
Pull Range
ppm
APR ppm
±0.5 ppm option
±2 ppm 20-year aging
T
±6.25
±2.75
R
±10
±6.50
Q
±12.5
±9.0
M
±25
±21.5
B
±50
±46.5
C
±80
±76.5
E
±100
±96.5
F
±125
±121.5
G
±150
±146.5
H
±200
±196.5
X
±400
±396.5
L
±600
±596.5
Y
±800
±796.5
S
±1200
±1196.5
Z
±1600
±1596.5
U
±3200
±3196.5
Notes:
14. APR includes initial tolerance, frequency stability vs. temperature, and the corresponding 20-year aging.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Output Frequency
The device powers up at the nominal operating frequency
and pull range specified by the ordering code. After power-
up both pull range and output frequency can be controlled
via I2C writes to the respective control registers. The
maximum output frequency change is constrained by the
pull range limits.
The pull range is specified by the value loaded in the
digital pull-range control register. The 16 pull range
choices are specified in the control register and range
from ±6.25 ppm to ±3200 ppm.
Table 19 below shows the frequency resolution versus pull
range programmed value
Table 19. Frequency Resolution versus Pull Range
Programmed Pull Range
Frequency Resolution
±6.25 ppm
5x10-12
±10 ppm
5x10-12
±12.5 ppm
5x10-12
±25 ppm
5x10-12
±50 ppm
5x10-12
±80 ppm
5x10-12
±100 ppm
5x10-12
±120 ppm
5x10-12
±150 ppm
5x10-12
±200 ppm
5x10-12
±400 ppm
1x10-11
±600 ppm
1.4x10-11
±800 ppm
2.1x10-11
±1200 ppm
3.2x10-11
±1600 ppm
4.7x10-11
±3200 ppm
9.4x10-11
The ppm frequency offset is specified by the 26 bit DCXO
frequency control register in two’s complement format as
described in the I2C Register Descriptions. The power up
default value is 00000000000000000000000000b which
sets the output frequency at its nominal value (0 ppm). To
change the output frequency, a frequency control word is
written to 0x00[15:0] (Least Significant Word) and
0x01[9:0] (Most Significant Word). The LSW value should
be written first followed by the MSW value; the frequency
change is initiated after the MSW value is written.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 24 of 38
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Figure 41. Pull Range and Frequency Control Word
Figure 41 shows how the two’s complement signed value of
the frequency control word sets the output frequency within
the ppm pull range set by 0x02:[3:0]. This example shows
use of the ±200 ppm pull range. Therefore, to set the
desired output frequency, one just needs to calculate the
fraction of full scale value ppm, convert to two’s
complement binary, and then write these values to the
frequency control registers.
The following formula generates the control word value:
Control word value = RND((225-1) × ppm shift from
nominal/pull range), where RND is the rounding function
which rounds the number to the nearest whole number.
Two examples follow, assuming a ±200 ppm pull range:
Example 1:
◼ Default Output Frequency = 19.2 MHz
◼ Desired Output Frequency = 19.201728 MHz (+90 ppm)
225-1 corresponds to +200 ppm, and the fractional value
required for +90 ppm can be calculated as follows.
◼ 90 ppm / 200 ppm × (225-1) = 15,099,493.95.
Rounding to the nearest whole number yields 15,099,494
and converting to two’s complement gives a binary value of
111001100110011001100110, or E66666 in hex.
Example 2:
◼ Default Output Frequency = 10 MHz
◼ Desired Output Frequency = 9.9995 MHz (-50 ppm)
Following the formula shown above,
◼ (-50 ppm / 200 ppm) × (225) = -8,388,608.
Converting this to two’s complement binary results in
11100000000000000000000000, or 3800000 in hex.
To summarize, the procedure for calculating the
frequency control word associated with a given ppm offset
is as follows:
It is important to note that the maximum Digital Control
update rate is 38 kHz regardless of I2C bus speed.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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I2C Control Registers
The SiT5155 enables control of frequency pull range, frequency pull value, and Output Enable via I2C writes to the control
registers. Table 20 below shows the register map summary, and detailed register descriptions follow.
Table 20. Register Map Summary
Address
Bits
Access
Description
0x00
[15:0]
RW
DIGITAL FREQUENCY CONTROL LEAST SIGNIFICANT WORD (LSW)
0x01
[15:11]
R
NOT USED
[10]
RW
OE Control. This bit is only active if the output enable function is under software control. If the device is
configured for hardware control using the OE pin, writing to this bit has no effect.
[9:0]
RW
DIGITAL FREQUENCY CONTROL MOST SIGNIFICANT WORD (MSW)
0x02
[15:4]
R
NOT USED
[3:0]
RW
DIGITAL PULL RANGE CONTROL
Register Descriptions
Register Address: 0x00. Digital Frequency Control Least Significant Word (LSW)
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Access
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
Default
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Name
DIGITAL FREQUENCY CONTROL LEAST SIGNIFICANT WORD (LSW)[15:0]
Bits
Name
Access
Description
15:0
DIGITAL FREQUENCY
CONTROL LEAST
SIGNIFICANT WORD
RW
Bits [15:0] are the lower 16 bits of the 26 bit FrequencyControlWord and are the Least
Significant Word (LSW). The upper 10 bits are in regsiter 0x01[9:0] and are the Most Significant
Word (MSW). The lower 16 bits together with the upper 10 bits specify a 26-bit frequency
control word.
This power-up default values of all 26 bits are 0 which sets the output frequency at its nominal
value. After power-up, the system can write to these two registers to pull the frequency across
the pull range. The register values are two’s complement to support positive and negative
control values. The LSW value should be written before the MSW value because the frequency
change is initiated when the new values are loaded into the MSW. More details and examples
are discussed in the previous section.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Register Address: 0x01. OE Control, Digital Frequency Control Most Significant Word (MSW)
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
Default
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Name
NOT USED
OE
DCXO FREQUENCY CONTROL[9:0] MSW
Bits
Name
Access
Description
15:11
NOT USED
R
Bits [15:10] are read only and return all 0’s when read. Writing to these bits has no
effect.
10
OE Control
RW
Output Enable Software Control. Allows the user to enable and disable the output
driver via I2C.
0 = Output Disabled (Default)
1 = Output Enabled
This bit is only active if the Output Enable function is under software control. If the
device is configured for hardware control using the OE pin, writing to this bit has no
effect.
9:0
DIGITAL FREQUENCY CONTROL
MOST SIGNIFICANT WORD (MSW)
RW
Bits [9:0] are the upper 10 bits of the 26 bit FrequencyControlWord and are the Most
Significant Word (MSW). The lower 16 bits are in register 0x00[15:0] and are the
Least Significant Word (LSW). These lower 16 bits together with the upper 10 bits
specify a 26-bit frequency control word.
This power-up default values of all 26 bits are 0 which sets the output frequency at its
nominal value. After power-up, the system can write to these two registers to pull the
frequency across the pull range. The register values are two’s complement to support
positive and negative control values. The LSW value should be written before the
MSW value because the frequency change is initiated when the new values are
loaded into the MSW. More details and examples are discussed in the previous
section.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 27 of 38
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Register Address: 0x02. DIGITAL PULL RANGE CONTROL[15]
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R
R
R
R
R
R
R
RW
RW
RW
RW
Default
0
0
0
0
0
0
0
0
0
0
0
0
X
X
X
X
Name
NONE
DIGITAL PULL RANGE CONTROL
Notes:
15. Default values are factory set but can be over-written after power-up.
Bits
Name
Access
Description
15:4
NONE
R
Bits [15:4] are read only and return all 0’s when read. Writing to these bits has no
effect.
3:0
DIGITAL PULL RANGE CONTROL
RW
Sets the digital pull range of the DCXO. The table below shows the available pull range
values and associated bit settings. The default value is factory programmed.
Bit
3 2 1 0
0 0 0 0: ±6.25 ppm
0 0 0 1: ±10 ppm
0 0 1 0: ±12.5 ppm
0 0 1 1: ±25 ppm
0 1 0 0: ±50 ppm
0 1 0 1: ±80 ppm
0 1 1 0: ±100 ppm
0 1 1 1: ±125 ppm
1 0 0 0: ±150 ppm
1 0 0 1: ±200 ppm
1 0 1 0: ±400 ppm
1 0 1 1: ±600 ppm
1 1 0 0: ±800 ppm
1 1 0 1: ±1200 ppm
1 1 1 0: ±1600 ppm
1 1 1 1: ±3200 ppm
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Serial Interface Configuration Description
The SiT5155 includes an I2C interface to access registers
that control the DCTCXO frequency pull range, and
frequency pull value. The SiT5155 I2C slave-only interface
supports clock speeds up to 1 Mbit/s. The SiT5155 I2C
module is based on the I2C specification, UM1024 (Rev.6
April 4, 2014 of NXP Semiconductor).
Serial Signal Format
The SDA line must be stable during the high period of the
SCL. SDA transitions are allowed only during SCL low level
for data communication. Only one transition is allowed
during the low SCL state to communicate one bit of data.
Figure 42 shows the detailed timing diagram.
An idle I2C bus state occurs when both SCL and SDA are
not being driven by any master and are therefore in a logic
HI state due to the pull up resistors. Every transaction
begins with a START (S) signal and ends with a STOP (P)
signal. A START condition is defined by a high to low
transition on the SDA while SCL is high. A STOP condition
is defined by a low to high transition on the SDA while SCL
is high. START and STOP conditions are always generated
by the master. This slave module also supports repeated
START (Sr) condition which is same as START condition
instead of STOP condition (the blue-color line shows
repeated START in Figure 43).
SDA
SCL
data line stable:
data valid change of data
allowed setup time
Figure 42. Data and clock timing relation in I2C bus
SDA
SCL S P
START Condition STOP Condition
hold time setup time
hold time
Figure 43. START and STOP (or repeated START, blue line) condition
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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Parallel Signal Format
Every data byte is 8 bits long. The number of bytes that can
be transmitted per transfer is unrestricted. Data is
transferred with the MSB (Most Significant Bit) first. The
detailed data transfer format is shown in the figures below.
The acknowledge bit must occur after every byte transfer
and it allows the receiver to signal the transmitter that the
byte was successfully received and another byte may be
sent. The acknowledge signal is defined as follows: the
transmitter releases the SDA line during the acknowledge
clock pulse so the receiver can pull the SDA line low and it
remains stable low during the high period of this clock
pulse. Setup and hold times must also be taken into
account. When SDA remains high during this ninth clock
pulse, this is defined as the Not-Acknowledge signal
(NACK). The master can then generate either a STOP
condition to abort the transfer, or a repeated START
condition to start a new transfer. The only condition that
leads to the generation of NACK from the SiT5155 is when
the transmitted address does not match the slave address.
When the master is reading data from the SiT5155, the
SiT5155 expects the ACK from the master at the end of
received data, so that the slave releases the SDA line and
the master can generate the STOP or repeated START. If
there is a NACK signal at the end of the data, then the
SiT5155 tries to send the next data. If the first bit of the next
data is “0”, then the SiT5155 holds the SDA line to “0”,
thereby blocking the master from generating a
STOP/(re)START signal.
Parallel Data Format
This I2C slave module supports 7-bit device addressing
format. The 8th bit is a read/write bit and “1” indicates a
read transaction and a “0” indicates a write transaction.
The register addresses are 8-bits long with an address
range of 0 to 255 (00h to FFh). Auto address incrementing
is supported which allows data to be transferred to
contiguous addresses without the need to write each
address beyond the first address. Since the maximum
register address value is 255, the address will roll from 255
back to 0 when auto address incrementing is used.
Obviously, auto address incrementing should only be
used for writing to contiguous addresses. The data
format is 16-bit (two bytes) with the most significant byte
being transferred first. For a read operation, the starting
register address must be written first. If that is omitted,
reading will start from the last address in the auto-
increment counter of the device, which has a startup
default of 0x00.
SDA
SCL S or
Sr P or
Sr
START Condition STOP Condition
MSB
1 2 7 8 9
ACK 1 2 3 to 8
acknowledge
from slave
9
ACK
acknowledge
from slave
Figure 44. Parallel signaling format
SDA
SCL S P
START
condition STOP
condition
8 91 to 7 91 to 8 91 to 8
slave
address W ACK ACK ACKdata-MSB
register
address
9
1 to 8
ACKdata-LSB
Figure 45. Parallel data byte format, write operation
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
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SDA
SCL S P
START
condition STOP
condition
8 91 to 7 91 to 8
slave
address R ACK ACKdata-MSB
9
1 to 8
ACKdata-LSB
Figure 46. Parallel data byte format, read operation
Figure 47 below shows the I2C sequence for writing the 4-byte control word using auto address incrementing.
STOP
condition
Output
Frequency
f0
Tfdelay
Tsettle
f0 + f1 ±0.5%
St D_Address[6:0] WA R_Address[7:0]=00 A
0x00[15:8]
A
0x00[7:0]
A
Digital Frequency Control – Least Significant Word (LSW) [15:0]
X X X X X OE
0x01[15:8]
A MSW[7:0] A Sp
Digital Frequency Control – Most Significant Word (MSW) [9:0]
LSW[15:8] LSW[7:0]
0x01[7:0]
9 8
Slave Drives Bit(s) on Bus
Master Drives Bit(s) on Bus
St Start
Sp Stop
W Write
R Read
A Acknowledge
OE Output Enable
X “Don’t Care” Register Bit not used.
Figure 47. Writing the Frequency Control Word
Table 21. DCTCXO Delay and Settling Time
Parameter
Symbol
Minimum
Typical
Maximum
Units
Notes
Frequency Change Delay
Tfdelay
–
103
140
µs
Time from end of 0x01 reg MSW to start of frequency pull, as
shown in Figure 47
Frequency Settling Time
Tsettle
–
16.5
20
µs
Time to settle to 0.5% of frequency offset, as shown in Figure 47
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 31 of 38
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I2C Timing Specification
The below timing diagram and table illustrate the timing relationships for both master and slave.
Figure 48. I2C Timing Diagram
Table 22. I2C Timing Requirements
Parameter
Speed Mode
Value
Unit
tSETUP
FM+ (1 MHz)
> 50
nsec
FM (400 KHz)
> 100
nsec
SM (100 KHz)
> 250
nsec
tHOLD
FM+ (1 MHz)
> 0
nsec
FM (400 KHz)
> 0
nsec
SM (100 KHz)
> 0
nsec
tVD:AWK
FM+
> 450
nsec
FM (400 KHz)
> 900
nsec
SM (100 KHz)
> 3450
nsec
tVD:DAT
NA (s-awk + s-data)/(m-awk/s-data)
master spec
both (slave/master) spec
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 32 of 38
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I2C Device Address Modes
There are two I2C address modes:
Table 23. Factory Programmed I2C Address Control[16]
I2C Address Ordering Code
Device I2C Address
0
1100000
1
1100001
2
1100010
3
1100011
4
1100100
5
1100101
6
1100110
7
1100111
8
1101000
9
1101001
A
1101010
B
1101011
C
1101100
D
1101101
E
1101110
F
1101111
Notes:
16. Table 23 is only valid for the DCTCXO device option which supports
I2C Control.
Table 24. Pin Selectable I2C Address Control [17]
A0
Pin 5
I2C Address
0
1100010
1
1101010
Notes:
17. Table 24 is only valid for the DCTCXO device option which supports
I2C control and A0 Device Address Control Pin.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 35 of 38
www.sitime.com
Layout Guidelines
◼ The SiT5155 uses internal regulators to minimize the
impact of power supply noise. For further reduction
of noise, it is essential to use two bypass capacitors
(0.1 μF and 10 μF). Place the 0.1 μF capacitor as
close to the VDD pin as possible, typically within
1 mm to 2 mm. Place the 10 μF capacitor within
2 inches of the device VDD and VSS pins.
◼ It is also recommended to connect all NC pins to the
ground plane and place multiple vias under the GND
pin for maximum heat dissipation.
◼ For additional layout recommendations, refer to the
Best Design Layout Practices.
Manufacturing Guidelines
The SiT5155 Super-TCXOs are precision timing devices.
Proper PCB solder and cleaning processes must be
followed to ensure best performance and long-term
reliability.
◼ No Ultrasonic or Megasonic Cleaning: Do not subject
the SiT5155 to an ultrasonic or megasonic cleaning
environment. Otherwise, permanent damage or long-term
reliability issues to the device may result.
◼ No external cover. Unlike legacy quartz TCXOs, the
SiT5155 is engineered to operate reliably, without
performance degradation in the presence of ambient
disturbers such as airflow and sudden temperature
changes. Therefore, the use of an external cover
typically required by quartz TCXOs is not needed.
◼ Reflow profile: For mounting these devices to the PCB,
IPC/JEDEC J-STD-020 compliant reflow profile must be
used. Device performance is not guaranteed if soldered
manually or with a non-compliant reflow profile.
◼ PCB cleaning: After the surface mount (SMT)/reflow
process, solder flux residues may be present on the PCB
and around the pads of the device. Excess residual solder
flux may lead to problems such as pad corrosion, elevated
leakage currents, increased frequency aging, or other
performance degradation. For optimal device performance
and long-term reliability, thorough cleaning to remove all
the residual flux and drying of the PCB is required as
shortly after the reflow process as possible. Water soluble
flux is recommended. In addition, it is highly
recommended to avoid the use of any “no clean” flux.
However, if the reflow process necessitates the use of “no
clean” flux, then utmost care should be taken to remove
all residual flux between SiTime device and the PCB.
Note that ultrasonic PCB cleaning should not be used with
SiTime oscillators.
◼ For additional manufacturing guidelines and marking/
tape-reel instructions, refer to SiTime Manufacturing
Notes.
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 36 of 38
www.sitime.com
Additional Information
Table 25. Additional Information
Document
Description
Download Link
ECCN #: EAR99
Five character designation used on the commerce
Control List (CCL) to identify dual use items for export
control purposes.
—
HTS Classification Code:
8542.39.0000
A Harmonized Tariff Schedule (HTS) code developed by
the World Customs Organization to classify/define
internationally traded goods.
—
Evaluation Boards
SiT6722EB Evaluation Board User Manual
https://www.sitime.com/support/user-guides
Demo Board
SiT6702DB Demo Board User Manual
https://www.sitime.com/support/user-guides
Time Machine II
MEMS oscillator programmer
http://www.sitime.com/support/time-machine-oscillator-programmer
Time Master Web-based
Configurator
Web tool to establish proper programming
https://www.sitime.com/time-master-web-based-configurator
Manufacturing Notes
Tape & Reel dimension, reflow profile and other
manufacturing related info
https://www.sitime.com/support/resource-library?filter=531
Qualification Reports
RoHS report, reliability reports, composition reports
http://www.sitime.com/support/quality-and-reliability
Performance Reports
Additional performance data such as phase noise,
current consumption and jitter for selected frequencies
http://www.sitime.com/support/performance-measurement-report
Termination Techniques
Termination design recommendations
http://www.sitime.com/support/application-notes
Layout Techniques
Layout recom mendations
http://www.sitime.com/support/application-notes
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 37 of 38
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Revision History
Table 26. Revision History
Version
Release Date
Change Summary
0.1
05/10/2016
First release, advanced information
0.15
08/04/2016
Replaced QFN package with SOIC-8 package
Added 10 µF bypass cap requirement
Updated test circuits to reflect both new bypass cap requirement and SOIC-8 package
Update Table 1 (Electrical Characteristics)
0.16
09/12/2016
Updated test circuit diagrams
0.2
09/21/2016
Revised Table 1 (Electrical Characteristics)
0.4
12/19/2016
Added DCTCXO mode
Added I2C information
Added I2C
0.5
07/21/2017
Added 5.0 mm x 3.2 mm package information
Updated Table 1 (Electrical Characteristics)
0.51
08/20/2017
Changed to preliminary
Updated 5.0 mm x 3.2 mm package dimensions
Updated test circuits
Updated Table 1 (Electrical Characteristics)
Updated part ordering info
Misc. corrections
0.52
11/24/2017
Updated the Thermal Characteristics table
Added more on Manufacturing Guideline section
0.55
02/05/2018
Added View labels to Package Drawings
Updated the frequency vs. output type changes to 60 MHz
Updated links and notes
0.60
03/01/2018
Added 105°C support, updated Ordering Information
1.0
07/06/2018
Updated Electrical Characteristics tables.
Added Performance Plots.
Improved readability.
Fixed bad hyperlinks.
1.01
08/03/2018
Added test circuit for clipped sinewave phase noise
Updated package outline drawing
Revised phase noise specifications
Updated conditions for one day and one year aging specs
Various formatting updates
1.02
12/04/2018
Formatting updates
Fixed APR typo for 125 ppm pull range and 0.5 ppm stability, Table 18
Corrected typos in package drawing dimensions
Added nominal value for LVCMOS output impedance
Increased Mechanical Shock Resistance to 30000g
Added “X” order code for 250u Tape and Reel
Improved I2C bus frequency specification
Updated Manufacturing Guidelines to recommend water soluble flux
1.03
03/28/2020
Corrected typos for write/read I2C polarity
Clarified PCB cleaning instructions
Added link to SiT6702DB
Added ECCN and HTS codes
Added note for Theta JA
Updated DCTCXO Delay and Settling Time table
Added max and min input voltage to Absolute Maximum Limits table
Updated output impedance typical spec
Changed phase noise measurement frequency for clipped sinewave to 20 MHz
Clarified Initial Tolerance specification condition
Relabeled “First Pulse Accuracy” parameter to “Time to Rated Frequency Stability” for clarity
1.04
05/23/2020
Revised Parallel Data Format section description and figures
SiT5155 ±0.5 ppm, Elite Platform™ Super-TCXO for GNSS/GPS
Rev 1.04
Page 38 of 38
www.sitime.com
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© SiTime Corporation 2016-2020. The information contained herein is subject to change at any time without notice. SiTime assumes no responsibility or liability for any loss, damage
or defect of a Product which is caused in whole or in part by (i) use of any circuitry other than circuitry embodied in a SiTime product, (ii) misuse or abuse including static discharge, neglect
or accident, (iii) unauthorized modification or repairs which have been soldered or altered during assembly and are not capable of being tested by SiTime under its normal test conditions, or
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