The Smart Timing Choice
The Smart Timing Choice
SiTime Corporation 990 Almanor Avenue, Sunnyvale, CA 94085 (408) 328-4400
Rev 0.85 Revised March 21, 2014
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
1. Contact Factory for SOT23-5 availability.
2. Core operating current does not include output driver operating current or load current. To derive total operating current (no load), add core operating current +
output driver operating current, which is a function of the output voltage swing. See the description titled, Calculating Load Current.
Features Applications
32.768 kHz ±5, ±10, ±20 ppm frequency stability options over temp Smart Meters (AMR)
Operating temperature ranges: Health and Wellness Monitors
0°C to +70°C Pulse-per-Second (pps) Timekeeping
-40°C to +85°C RTC Reference Clock
Three package options: 2.0 x 1.2 mm (2012) SMD, SOT23-5[1],
1.5 x 0.8 mm CSP
Ultra-low power: <1 µA
Vdd supply range: 1.5V to 3.63V
Improved stability reduces system power with fewer network
timekeeping updates
NanoDrive™ programmable output swing for lowest power and direct
XTAL SoC input interface
Internal filtering eliminates external Vdd bypass cap and saves space
Pb-free, RoHS and REACH compliant
Electrical Characteristics
Parameter Symbol Min. Typ. Max. Unit Condition
Frequency and Stability
Output Frequency Fout 32.768 kHz
Initial Tolerance F_init -5.0 5.0 ppm TA = 25°C, includes reflow. Tested with Agilent 53132A freq.
counter, gate time 100ms.
Frequency Stability Over
Temperature F_stab
-5.0 5.0
Stability part number code = E, includes ±20% load variation
-10 10 Stability part number code = F, includes ±20% load variation
-20 20 Stability part number code = 1, includes ±20% load variation
Frequency Stability vs Voltage F_vdd -0.75 0.75 ppm 1.8V ±10%
-1.5 1.5 ppm 1.5V – 3.63V
First Year Frequency Aging F_aging -1.0 1.0 ppm TA = 25°C, Vdd = 3.0V
Jitter Performance (TA = over temp)
Long Term Jitter 2.5 µspp 81920 cycles (2.5 sec), 100 samples
Period Jitter 35 nsRMS N = 10,000, TA = 25°C, Vdd = 1.5V – 3.63V
Supply Voltage and Current Consumption
Operating Supply Voltage Vdd 1.5 3.63 V TA = -40°C to +85°C
Core Supply Current Idd 0.99 μATA = 25°C, Vdd = 1.8V, LVCMOS Output configuration, No Load
1.52 TA = -40°C to +85°C, Vdd = 1.5V – 3.63V, No Load
Power-Supply Ramp t_Vdd_
Ramp 100 ms Vdd Ramp-Up 0 to 90% Vdd, TA = -40°C to +85°C
Start-up Time at Power-up t_start 200 300 ms Valid Output with frequency stability specifications.
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 2 of 9
Electrical Characteristics (continued)
Parameter Symbol Min. Typ. Max. Unit Condition
Operating Temperature Range
Commercial Temperature
Industrial Temperature -40 85 °C
Extended Industrial
Temperature -40 105 °C Contact Factory for availability
Output Rise/Fall Time tr, tf 100 200 ns 10-90%, 15 pF Load
Output Clock Duty Cycle DC 48 52 %
Output Voltage High VOH 90% V Vdd: 1.5V – 3.63V. IOH = -1 μA, 15 pF Load
Output Voltage Low VOL 10% V Vdd: 1.5V – 3.63V. IOL = 1 μA, 15 pF Load
NanoDrive™ Reduced Swing Output
Output Rise/Fall Time tf, tf 200 ns 10-90%, 15 pF Load
Output Clock Duty Cycle DC 48 52 %
AC-coupled Programmable
Output Swing V_sw 0.20 to
0.80 V
SiT1552 does not internally AC-couple. This output description
is intended for a receiver that is AC-coupled.
Vdd: 1.5V – 3.63V, 10 pF Load, IOH / IOL = ±0.2 μA
DC-Biased Programmable
Output Voltage High Range VOH 0.6 to
1.225 V Vdd: 1.5V – 3.63V. IOH = -0.2 μA, 10 pF Load
DC-Biased Programmable
Output Voltage Low Range VOL 0.35 to
0.80 V Vdd: 1.5V – 3.63V. IOL = 0.2 μA, 10 pF Load
Programmable Output Voltage
Swing Tolerance -0.055 0.055 V TA = -40°C to +85°C, Vdd = 1.5V to 3.63V. See Tables 1 and -2
for acceptable NanoDrive Settings.
Pin Configuration
Pin Symbol I/O Functionality
1 n/a 2 NC No Connect
No Connect. Will not respond to any input signal. When interfacing to
an MCU’s XTAL input pins, this pin is typically connected to the
receiving IC’s X Out pin. In this case, the SiT1552 will not be affected
by the signal on this pin. If not interfacing to an XTAL oscillator, leave
pin 1 floating (no connect).
2 1, 4 1, 5 GND Power Supply
Connect to ground. All GND pins must be connected to power supply
ground. The GND pins on the SOT23 and CSP packages can be
connected together, as long as both GND pins are connected ground.
3 2 4 CLK Out OUT
Oscillator clock output. When interfacing to an MCU’s XTAL, the CLK
Out is typically connected to the receiving IC’s X IN pin. The SiT1552
oscillator output includes an internal driver. As a result, the output
swing and operation is not dependent on capacitive loading. This
makes the output much more flexible, layout independent, and robust
under changing environmental and manufacturing conditions.
4 3 3 Vdd Power Supply
Connect to power supply 1.5V Vdd 3.63V. Under normal operating
conditions, Vdd does not require external bypass/decoupling
capacitor(s). Internal power supply filtering will reject more than 500
mVpp with frequency components through 10 MHz.
Contact factory for applications that require a wider operating supply
voltage range.
SMD Package (Top View) CSP Package (Top View) SOT23-5 Package (Top View)
GND 14
NC 2
Vdd 3OUT
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 3 of 9
System Block Diagram
Figure 1.
Absolute Maximum
Attempted operation outside the absolute maximum ratings 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 Condition Value Unit
Continuous Power Supply Voltage Range (Vdd) -0.5 to 3.63 V
Short Duration Maximum Power Supply Voltage (Vdd) 30 minutes 4.0 V
Continuous Maximum Operating Temperature Range Vdd = 1.5V - 3.63V 105 °C
Short Duration Maximum Operating Temperature Range Vdd = 1.5V - 3.63V, 30 mins 125 °C
Human Body Model (HBM) ESD Protection JESD22-A114 3000 V
Charge-Device Model (CDM) ESD Protection JESD22-A115 750 V
Machine Model (MM) ESD Protection JESD22-C101 300 V
Latch-up Tolerance JESD78 Compliant
Mechanical Shock Resistance Mil 883, Method 2002 10,000 g
Mechanical Vibration Resistance Mil 883, Method 2007 70 g
2012 SMD Junction Temperature 150 °C
1508 CSP Junction Temperature 150 °C
SOT23-5 Junction Temperature 150 °C
Storage Temperature -65°C to 150°C
Thermal Consideration
JA, 4 Layer Board
JA, 2 Layer Board
JC, Bottom
2012 SMD TBD
1508 CSP TBD
NC or
MEMS Resonator
Control Temp-to-Digital NVM
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 4 of 9
The SiT1552 is an ultra-small and ultra-low power 32.768 kHz
TCXO optimized for battery-powered applications. SiTime’s
silicon MEMS technology enables the first 32 kHz TCXO in
the world’s smallest footprint and chip-scale packaging
(CSP). Typical core supply current is only 1 µA. And unlike
standard oscillators, the SiT1552 features NanoDrive™, a
factory programmable output that reduces the voltage swing
to minimize power.
SiTime’s MEMS oscillators consist of MEMS resonators and
a programmable analog circuit. Our MEMS resonators are
built with SiTime’s unique MEMS First™ process. A key
manufacturing step is EpiSeal™ during which the MEMS
resonator is annealed with temperatures over 1000°C.
EpiSeal creates an extremely strong, clean, vacuum chamber
that encapsulates the MEMS resonator and ensures the best
performance and reliability. During EpiSeal, a poly silicon cap
is grown on top of the resonator cavity, which eliminates the
need for additional cap wafers or other exotic packaging. As
a result, SiTime’s MEMS resonator die can be used like any
other semiconductor die. One unique result of SiTime’s
MEMS First and EpiSeal manufacturing processes is the
capability to integrate SiTime’s MEMS die with a SOC, ASIC,
microprocessor or analog die within a package to eliminate
external timing components and provide a highly integrated,
smaller, cheaper solution to the customer.
TCXO Frequency Stability
The SiT1552 is factory calibrated (trimmed) over multiple
frequency points to guarantee extremely tight stability over
temperature. Unlike quartz crystals that have a classic tuning
fork parabola temperature curve with a 25°C turnover point
with a 0.04 ppm/C2 temperature coefficient, the SiT1552
temperature coefficient is calibrated and corrected over
temperature with an active temperature correction circuit. The
result is 32 kHz TCXO with extremely tight frequency variation
over the -40°C to +85°C temperature range. Contact SiTime
for applications that require a wider supply voltage range
>3.63V, or lower operating frequency below 32 kHz.
When measuring the SiT1552 output frequency with a
frequency counter, it is important to make sure the counter's
gate time is >100ms. The slow frequency of a 32kHz clock will
give false readings with faster gate times.
Power Supply Noise Immunity
In addition to eliminating external output load capacitors
common with standard XTALs, this device includes special
power supply filtering and thus, eliminates the need for an
external Vdd bypass-decoupling capacitor to keep the
footprint as small as possible. Internal power supply filtering
is designed to reject more than 500 mV noise and frequency
components from low frequency to more than 10 MHz.
Start-up and Steady-State Supply Current
The SiT1552 TCXO starts-up to a valid output frequency
within 300 ms (150ms typ). To ensure proper start-up, Vdd
power-supply ramp, from a power-down state to 90% of final
Vdd, must be less than 100ms.
During initial power-up, the SiT1552 power-cycles internal
blocks, as shown in the power-supply start-up and steady
state plot in the Typical Operating Curves section. Power-up
and initialization is typically 200 ms, and during that time, the
peak supply current reaches 28 µA as the internal capacitors
are charged, then sequentially drops to its 990 nA
steady-state current. During steady-state operation, the
internal temperature compensation circuit turns on every 350
ms for a duration of approximately 10 ms.
Output Voltage
The SiT1552 has two output voltage options. One option is a
standard LVCMOS output swing. The second option is the
NanoDrive reduced swing output. Output swing is customer
specific and Factory programmed between 200 mV and 800
mV. For DC-coupled applications, output VOH and VOL are
individually factory programmed to the customers’
requirement. VOH programming range is between 600 mV
and 1.225V in 100 mV increments. Similarly, VOL
programming range is between 350 mV and 800 mV. For
example; a PMIC or MCU is internally 1.8V logic compatible,
and requires a 1.2V VIH and a 0.6V VIL. Simply select SiT1552
NanoDrive factory programming code to be “D14” and the
correct output thresholds will match the downstream PMIC or
MCU input requirements. Interface logic will vary by manufac-
turer and we recommend that you review the input voltage
requirements for the input interface.
For DC-biased NanoDrive output configuration, the minimum
VOL is limited to 350mV and the maximum allowable swing
(VOH - VOL) is 750mV. For example, 1.1V VOH and 400mV
VOL is acceptable, but 1.2V VOH and 400 mV VOL is not
When the output is interfacing to an XTAL input that is inter-
nally AC-coupled, the SiT1552 output can be Factory
programmed to match the input swing requirements. For
example, if a PMIC or MCU input is internally AC-coupled and
requires an 800mV swing, then simply choose the SiT1552
NanoDrive programming code “AA8” in the part number. It is
important to note that the SiT1552 does not include internal
AC-coupling capacitors. Please see the Part Number
Ordering section at the end of the datasheet for more infor-
mation about the part number ordering scheme.
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 5 of 9
SiT1552 NanoDrive
Figure 3 shows a typical output waveform of the SiT1552 (into
a 10 pF load) when factory programmed for a 0.70V swing and
DC bias (VOH/VOL) for 1.8V logic:
NanoDrive part number coding: D14. Example part
number: SiT1552AI-J4-D14-32.768
OH = 1.1V, VOL = 0.4V (Vsw = 0.70V)
Figure 2. SiT1552AI-J4-D14-32.768
Output Waveform (10 pF load)
Table 1 shows the supported NanoDrive VOH, VOL factory
programming options.
Table 2 shows the supported AC coupled Swing levels. The
“AC-coupled” terminology refers to the programming
description for applications where the downstream chipsets
includes an internal AC-coupling capacitor, and therefore, only
the output swing is important and VOH/VOL is not relevant. For
these applications, refer to Table 2 for the acceptable voltage
swing options.
NanoDrive part number coding: AA2. Example part number:
Output voltage swing: 0.250V
The values listed in Tables 1 and -2 are nominal values at 25°C
and will exhibit a tolerance of ±55 mV across Vdd and -40°C
to 85°C operating temperature range.
SiT1552 Full Swing LVCMOS Output
Figure 3. LVCMOS Waveform
(Vdd = 1.8V) into 15 pF Load
LVCMOS output part number coding is always DCC
Example part number: SiT1552AI-J4-DCC-32.768
Table 1. Acceptable VOH/VOL NanoDrive Levels
VOL/VOH 1.225 1.100 1.000 0.900 0.800 0.700 0.600
0.800 D28 D18 D08
0.700 D27 D17 D07 D97
0.525 D26 D16 D06 D96 D86
0.500 D25 D15 D05 D95 D85 D75
0.400 D14 D04 D94 D84 D74 D64
0.350 D13 D03 D93 D83 D73 D63
Table 2. Acceptable NanoDrive Voltage Swing Options
(for downstream AC-coupled receivers)
Swing 0.800 0.700 0.600 0.500 0.400 0.300 0.250 0.200
Code AA8 AA7 AA6 AA5 AA4 AA3 AA2 AA1
VOH = 1.1V
VSW = 0.7V
VOL = 0.4V
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 6 of 9
Typical Operating Curves
(TA = 25°C, Vdd = 1.8V, unless otherwise stated)
Initial Tolerance Histogram
Frequency Stability Over Temperature
Start-up and Steady-State Current Profile
NanoDrive™ Output Waveform
(VOH = 1.2V, VOL = 0.4V, 10 pF Load;
LVCMOS Output Waveform
(SiT1552AI-JE-DCC-32.768, 10 pF Load)
-10 -5 0 5 10
Initial Tolerance (ppm)
TA = 25°C Post Reflow
Number of Devices
Min/Max Limit
-40 -20 020 40 60 80
Ambient Temperature (°C)
5 ppm Option (E)
200 units
VOH = 1.1V
VSW = 0.7V
VOL = 0.4V
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 7 of 9
Calculating Load Current
No Load Supply Current
When calculating no-load power for the SiT1552, the core and
output driver components need to be added. Since the output
voltage swing can be programmed to minimize load current,
the output driver current is variable. Therefore, no-load
operating supply current is broken into two sections; core and
output driver. The equation is as follows:
Total Supply Current (no load) = Idd Core + Idd Output Driver
Example 1: Full-swing LVCMOS
Vdd = 1.8V
Idd Core = 990nA (typ)
pp = 1.8V
Idd Output Driver: (Cdriver)(Vout)(Fout) =
(3.5pF)(1.8V)(32768Hz) = 206nA
Supply Current = 990nA + 206nA = 1.2µA
Example 2: NanoDrive Reduced Swing
Vdd = 1.8V
Idd Core = 990nA (typ)
pp (Programmable) = VOH – VOL = 1.1V - 0.6V = 500mV
Idd Output Driver: (Cdriver)(Vout)(Fout) =
(3.5pF)(0.50V)(32768Hz) = 57nA
Supply Current = 990nA + 57nA = 1.05µA
Total Supply Current with Load
To calculate the total supply current, including the load, follow
the equation listed below. Note the 30% reduction in power
with NanoDrive.
Total Current = Idd Core + Idd Output Driver + Load Current
Example 1: Full-swing LVCMOS
Vdd = 1.8V
Idd Core = 990nA
Load Capacitance = 10pF
Idd Output Driver: (Cdriver)(Vout)(Fout) =
(3.5pF)(1.8V)(32768Hz) = 206nA
Load Current: (10pF)(1.8V)(32768Hz) = 590nA
Total Current = 990nA + 206nA + 590nA = 1.79µA
Example 2: NanoDrive Reduced Swing
Vdd = 1.8V
Idd Core = 990nA
Load Capacitance = 10pF
(Programmable): VOH – VOL = 1.1V - 0.6V = 500mV
Idd Output Driver: (Cdriver)(Vout)(Fout) =
(3.5pF)(0.5V)(32768Hz) = 57nA
Load Current: (10pF)(0.5V)(32768Hz) = 164nA
Total Current = 990nA + 57nA + 164nA = 1.2µA
The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Rev. 0.85 Page 8 of 9
3. Top marking: Y denotes manufacturing origin and XXXX denotes manufacturing lot number. The value of “Y” will depend on the assembly location of the device.
Dimensions and Patterns
Package Size – Dimensions (Unit: mm)[3] Recommended Land Pattern (Unit: mm)
2.0 x 1.2 mm SMD
1.55 x 0.85 mm CSP
2.90 x 2.80 mm SOT23-5
#3 #1
#1 #2
#4 #3
#2 #1
#3 #4
1.54 ±0.02
0.84 ±0.02
0.315 ±0.015
#1 #2
#4 #3
SOT23-5 Dimension Table
Symbol Min. Nom. Max.
A 0.90 1.27 1.45
A1 0.00 0.07 0.15
A2 0.90 1.2 1.30
b 0.30 0.35 0.50
c 0.14 0.153 0.20
Symbol Min. Nom. Max.
E1 1.60
e1 1.90
L 0.30 0.38 0.55
L1 0.25
Rev. 0.85 Page 9 of 9
© SiTime Corporation 2014. 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 (iv) improper
installation, storage, handling, warehousing or transportation, or (v) being subjected to unusual physical, thermal, or electrical stress.
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The Smart Timing Choice
The Smart Timing Choice
Ultra-Low Power, Ultra-Small 32.768 kHz MEMS TCXO
Ordering Information
Part number characters in blue represent the customer specific options. The other characters in the part number are fixed.
The following examples illustrate how to select the appropriate part number scheme:
Part Family
Revision Letter
“A”: is the revision
Temperature Range
“I”: Industrial, -40 to 85ºC
DC-coupled Output VOL or
AC Swing
“1”: 200mV (only available with
AC-coupled option)
“2”: 250mV (only available with
AC-coupled option)
“3”: 350mV
“4”: 400mV
“5”: 500mV
“6”: 600mV
“7”: 700mV
“8”: 800mV
“C”: rail-to-rail LVCMOS
Blank for Bulk
Samples in cut Tape & Reel strips
“C”: Commercial, 0 to 70ºC
Package Size
“S”: 8 mm Tape & Reel, 10ku reel
“J”: 1.5 mm x 0.8 mm CSP
“D”: 8 mm Tape & Reel, 3ku reel
“E”: 8 mm Tape & Reel, 1ku reel
Stability Options
“E”: 5 ppm
DC-coupled Output VOH
“6”: 600mV
“7”: 700mV
“8”: 800mV
“9”: 900mV
“0”: 1.00V
“1”: 1.10V
“2”: 1.225V
“A”: AC-coupled Receiver
“C”: rail-to-rail LVCMOS
“H”: 2.0 mm x 1.2 mm SMD
Output Clock Frequency (kHz)
“S”: SOT23-5
“1”: 20 ppm
“F”: 10 ppm
32.768 kHz
AC- or DC-coupled
“A”: AC-coupled Signal Path Rx
“D”: DC-coupled Signal Path or
Rail-to-Rail LVCMOS
Example 1: SiT1552AI-JE-DCC-32.768
Industrial temperature range
CSP package
5 ppm frequency stability
Output requirements:
a) Output frequency = 32.768 kHz
b) “D” = DC-coupled receiver
c) “C” = LVCMOS output swing
d) “C” = LVCMOS output swing
Example 2: SiT1552AI-SF-AA5-32.768
Industrial temperature range
SOT23-5 package
10 ppm frequency stability
Output requirements:
a) Output frequency = 32.768 kHz
b) “A” = AC-coupled receiver
c) “A” = AC-coupled receiver
d) “5” = 500mV swing