LTC6905-XXX Series
1
6905xfa
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
No External Components to Set Frequency
■
Frequency Error: ±0.5% Typical
■
Fast Start-Up Time: 100µs Typical
■
±20ppm/°C Temperature Stability
■
Includes Output Enable
■
Includes Frequency Divide by 1, 2 or 4
■
Rise Time: 0.5ns, C
L
= 5pF
■
Timing Jitter: <0.8% Typical
■
Duty Cycle: 50% ±2.5%
■
I
S
= 8mA Typical (f
OSC
= 100MHz, C
L
= 5pF)
■
CMOS Output Drives 600Ω Load
■
Single Supply 2.7V to 5.5V
■
Low Profile (1mm) ThinSOT
TM
Package
Fixed Frequency
SOT-23 Oscillator
■
Data Clocks for High Reliability Applications
■
High Vibration, High Acceleration Environments
■
Replacement for Fixed Crystal and Ceramic
Oscillators
The LTC
®
6905-XXX series are precision, fixed frequency
silicon oscillators designed to minimize board space while
maximizing accuracy and ease of use.
Programmed at the factory to a fixed frequency, the
LTC6905-XXX series of parts need no external trim com-
ponents. An internal three-state divider allows for division
of the master clock by 1, 2 or 4, providing 3 frequencies
(for each device).
The LTC6905-XXX series operate with a single 2.7V to
5.5V power supply and provide a rail-to-rail, 50% duty
cycle, square wave output. The OE pin will disable the
output when brought low and synchronously enable the
output when brought high, avoiding pulse slivers.
The four products of the LTC6905-XXX family are:
LTC6905-133: f
OSC
= 133MHz, 66.7MHz, 33.3MHz
LTC6905-100: f
OSC
= 100MHz, 50MHz, 25MHz
LTC6905-96: f
OSC
= 96MHz, 48MHz, 24MHz
LTC6905-80: f
OSC
= 80MHz, 40MHz, 20MHz
The LTC6905-XXX series of parts provides a factory trim
option to modify the divider ratios from 1, 2, 4 to 8, 16, 32.
A second trim option allows for additional master clock
frequencies. For the alternate divider ratios and unlisted
frequencies, contact LTC marketing.
Basic Connection
Typical Distribution of Frequency Error, TA = 25°C
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6614313, 6342817.
V+
1
2
3
5
fOSC = 133MHz
3V
3V
0.1µF
6905x TA01
4
GND
LTC6905-133
OE
OUT
DIV OPEN
÷2
÷1
÷4
% FREQUENCY ERROR
–1
0
UNITS
10
20
30
40 VS = 3V
–0.5 0.0 0.5
6905x TA02
1
LTC6905-XXX Series
2
6905xfa
Supply Voltage (V
+
) to GND ........................–0.3V to 6V
DIV to GND .................................... –0.3V to (V
+
+ 0.3V)
OE to GND ..................................... – 0.3V to (V
+
+ 0.3V)
Output Short-Circuit Duration (Note 6) ........... Indefinite
Operating Temperature Range (Note 8)
LTC6905C .......................................... –40°C to 85°C
LTC6905I............................................ – 40°C to 85°C
LTC6905H ........................................ – 40°C to 125°C
Specified Temperature Range (Note 8)
LTC6905C ............................................... 0°C to 70°C
LTC6905I............................................ – 40°C to 85°C
LTC6905H ........................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
T
JMAX
= 125°C, θ
JA
= 150°C/W
LTC6905CS5-133
LTC6905IS5-133
LTC6905HS5-133
LTC6905CS5-100
LTC6905IS5-100
LTC6905HS5-100
LTC6905CS5-96
LTC6905IS5-96
LTC6905HS5-96
LTC6905CS5-80
LTC6905IS5-80
LTC6905HS5-80
(Note 1)
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC SOT-23
1
2
3
V+
GND
OE
5
4
OUT
DIV
S5 PART MARKING*
LTBPM
LTBPM
LTBPM
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
*The temperature grade is identified by a label on the shipping container.
LTBPK
LTBPK
LTBPK
LTBPJ
LTBPJ
LTBPJ
LTBPH
LTBPH
LTBPH
The ● denotes the specifications which apply over the full specified
temperature range, otherwise specifications are at TA = 25°C or as noted. OE = DIV = V+, V+ = 2.7V to 3.6V, RL = 15k, CL = 5pF, unless
otherwise noted. All voltages are with respect to GND.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
∆f Frequency Accuracy (Notes 2, 7) LTC6905C-XXX
T
A
= 25°C, V
+
= 3V ±0.5 ±1.0 %
0°C < T
A
< 70°C●±1.5 %
LTC6905I-XXX
25°C < T
A
< 85°C±1.8 %
–40°C < T
A
< 85°C●±2.9 %
LTC6905H-XXX
25°C < T
A
< 125°C±2.3 %
–40°C < T
A
< 125°C●±2.9 %
V
+
= 5V ±1.5 %
∆f/∆T Freq Drift Over Temp (Note 2) ●±20 ppm/°C
∆f/∆V Freq Drift Over Supply (Notes 2, 7) V
+
= 2.7V to 3.6V 0.5 %/V
Timing Jitter (Note 3) 0.8 %
Long-Term Stability of Output Frequency 300 ppm/√kHr
ELECTRICAL CHARACTERISTICS
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
LTC6905-XXX Series
3
6905xfa
The ● denotes the specifications which apply over the full specified
temperature range, otherwise specifications are at TA = 25°C or as noted. OE = DIV = V+, V+ = 2.7V to 3.6V, RL = 15k, CL = 5pF, unless
otherwise noted. All voltages are with respect to GND.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Duty Cycle DIV = 0V ●47.5 50 52.5 %
V
+
Operating Supply Range ●2.7 5.5 V
I
S
Power Supply Current DIV = V
+
(÷ 1), V
+
= 3.6V
LTC6905-133 ●10 15 mA
LTC6905-100 ●812 mA
LTC6905-96 ●812 mA
LTC6905-80 ●711 mA
DIV = 0 (÷ 4), V
+
= 3.6V
LTC6905-133 ●58 mA
LTC6905-100 ●47 mA
LTC6905-96 ●47 mA
LTC6905-80 ●3.5 6 mA
V
IH
High Level DIV or OE Pins Input Voltage ● V
+
– 0.15 V
V
IL
Low Level DIV or OE Pins Input Voltage ●0.2 V
I
DIV
DIV Input Current (Note 4) DIV = V
+
V
+
= 5.5V ● 15 40 µA
DIV = 0V V
+
= 5.5V ●–40 –11 µA
I
OE
OE Input Current (Note 4) OE = V
+
V
+
= 5.5V 15 µA
OE = 0V V
+
= 5.5V –11 µA
V
OH
High Level Output Voltage (Note 4) V
+
= 5.5V I
OH
= –1mA ●5.25 5.45 V
I
OH
= –4mA ●5.20 5.30 V
V
+
= 2.7V I
OH
= –1mA ●2.5 2.6 V
I
OH
= –4mA ●2.3 2.5 V
V
OL
Low Level Output Voltage (Note 4) V
+
= 5.5V I
OL
= 1mA ●0.05 0.25 V
I
OL
= 4mA ●0.2 0.3 V
V
+
= 2.7V I
OL
= 1mA ●0.1 0.3 V
I
OL
= 4mA ●0.4 0.5 V
t
r
,
t
f
OUT Rise/Fall Time (Note 5) 0.5 ns
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Frequency accuracy is tested with DIV = V
+
(÷1). Other divide
ratios are guaranteed by design.
Note 3: Jitter is the ratio of the peak-to-peak distribution of the period to
the mean of the period. This specification is based on characterization and
is not 100% tested.
Note 4: To conform with the Logic IC Standard convention, current out of
a pin is arbitrarily given as a negative value.
Note 5: Output rise and fall times are measured between the 10% and
90% power supply levels.
Note 6: A heat sink may be required to keep the junction temperature
below the absolute maximum when the output is shorted indefinitely.
Note 7: The LTC6905 is optimized for the performance with a 3V power
supply voltage. Refer to Typical Performance Characteristics curves in this
data sheet for additional information regarding the LTC6905 voltage
coefficient, especially between 4.5V and 5.5V. Please consult LTC
Marketing for parts optimized for 5V operation.
Note 8: The LTC6905C-XXX is guaranteed functional over the operating
temperature range and is guaranteed to meet specified performance from
0°C to 70°C. The LTC6905C-XXX is designed, characterized and expected
to meet specified performance from –40°C to 85°C but is not tested or QA
sampled at these temperatures. The LTC6905I-XXX is guaranteed to meet
specified performance from –40°C to 85°C.
LTC6905-XXX Series
4
6905xfa
LTC6905-80 Output Operating at
20MHz, VS = 3V
LTC6905-133 Output Operating at
133MHz, VS = 3V
ROUT vs V+Jitter vs Frequency
SUPPLY VOLTAGE (V)
2.5
0
OUTPUT RESISTANCE (Ω)
5
15
20
25
4.5
45
6905x G04
10
3.5
35
4 5.5
30
35
40
FREQUENCY (MHz)
0
0
JITTER (%)
0.20
0.60
÷4÷2÷1
0.80
1.00
40 80 100 180
6905x G05
0.40
20 60 120 140 160
1.20
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Frequency vs Temperature
TEMPERATURE (°C)
–40
–1.0
PERCENTAGE ERROR (%)
–0.8
–0.4
–0.2
0
1.0
0.4
040 60
6905x G08
–0.6
0.6
0.8
0.2
–20 20 80 100 120
Supply Current vs Frequency
FREQUENCY (MHz)
0
SUPPLY CURRENT (mA)
10
12
14
200
6905x G01
8÷4
÷4
÷1
÷1
6
0
2
50 100 150
4
18
16
5.5V
2.7V
÷2
÷2
Frequency Error vs Supply Voltage
SUPPLY VOLTAGE (V)
2.5
–0.50
FREQUENCY ERROR (%)
O
0.50
1.00
1.50
2.50
33.5 4 4.5
6905x G09
5 5.5
2.00
LTC6905-133
LTC6905-100
LTC6905-96
LTC6905-80
0.75V/DIV
10ns/DIV
6905x G06
0.75V/DIV
2.5ns/DIV 6905x G07
LTC6905-XXX Series
5
6905xfa
BLOCK DIAGRA
W
–
+
–
+
+
–
1
3
GAIN = 1
V
+
V
BIAS
I
RES
I
RES
R
SET
GND
MASTER OSCILLATOR
PROGRAMMABLE
DIVIDER
(N = 1, 2 OR 4)
V
RES
= 1V ±5%
(V
+
– V
SET
)
THREE-STATE
INPUT DETECT
GND
V
+
15µA
6905x BD
15µA
OUT
OE
f
MO
DIVIDER
SELECT
5
DIV 4
2
f
OSC
= f
MO
N
UU
U
PI FU CTIO S
V
+
(Pin 1): Voltage Supply (2.7V ≤ V
+
≤ 5.5V). This supply
must be kept free from noise and ripple. It should be
bypassed directly to the GND (Pin 2) with a 0.1µF capacitor
or higher.
GND (Pin 2): Ground. Should be tied to a ground plane for
best performance.
OE (Pin 3): Output Enable. Pull to V+ or leave floating to
enable the output driver (Pin 5). Pull low to disable the
output. The output is disabled asynchronously. Pulling OE
pin low will immediately disable the output. Pulling the OE
pin high will bring the output high on the next low to high
transition of the clock. This eliminates pulse slivers.
DIV (Pin 4): Divider-Setting Input. This three-state input
selects among three divider settings. Pin 4 should be tied
to V
+
for the ÷1 setting, the highest frequency range. Float-
ing Pin 4 divides the master oscillator by 2. Pin 4 should
be tied to GND for the ÷4 setting, the lowest frequency range.
To detect a floating DIV pin, the LTC6905 attempts to pull
the pin toward midsupply. This is realized with two internal
current sources, one tied to V
+
and Pin 4 and the other one
tied to ground and Pin 4. Therefore, driving the DIV pin high
requires sourcing approximately 15µA. Likewise, driving
DIV low requires sinking 15µA. When Pin 4 is floated, it
should be bypassed by a 1nF capacitor to ground or it should
be surrounded by a ground shield to prevent excessive cou-
pling from other PCB traces.
OUT (Pin 5): Oscillator Output. This pin can drive 5kΩ
and/or 5pF loads. For heavier loads, refer to the Applica-
tions Information section.
Table 1. LTC6905-XXX Frequency Settings
DIV SETTING LTC6905-133 LTC6905-100 LTC6905-96 LTC6905-80
V+ 133.33MHz 100MHz 96MHz 80MHz
OPEN 66.66MHz 50MHz 48MHz 40MHz
GND 33.33MHz 25MHz 24MHz 20MHz
LTC6905-XXX Series
6
6905xfa
APPLICATIO S I FOR ATIO
WUUU
START-UP TIME
The start-up and settling time to within 1% of the final
frequency is typically 100µs.
MAXIMUM OUTPUT LOAD
The LTC6905 output (Pin 5) can drive a capacitive load
(C
LOAD
) of 5pF or more. Performance driving a C
LOAD
greater than 5pF depends on the oscillator’s frequency
(f
OSC
) and output resistance (R
OUT
). The output rise time
or fall time due to R
OUT
and C
LOAD
is equal to 2.2 •
R
OUT
•
C
LOAD
(from 10% to 90% of the rise or fall transition). If the
total output rise time plus fall time is arbitrarily specified
to be equal to or less than 20% of the oscillator’s period (1/
f
OSC
), then the maximum output C
LOAD
in
picofarads (pF)
should be equal to or less than [45454/(R
OUT
•
f
OSC
)]
(R
OUT
in ohms and f
OSC
in MHz).
Example: An LTC6905-100 is operating with a 3V power
supply and is set for a f
OSC
= 50MHz.
R
OUT
with V
+
= 3V is 27Ω (using the R
OUT
vs V
+
graph in
the Typical Performance Characteristics).
The maximum output C
LOAD
should be
equal to or less
than [45454/(27 • 50)] = 33.6pF.
The lowest resistive load Pin 5 can drive can be calculated
using the minimum high level output voltage in the Elec-
trical Characteristics. With a V
+
equal to 5.5V and 4mA
output current, the minimum high level output voltage is
5.2V and the lowest resistive load Pin 5 can drive is 1.30k
(5.2V/4mA). With a V
+
equal to 2.7V and 4mA output
current, the minimum high level output voltage is 2.4V and
the lowest resistive load Pin 5 can drive is 600Ω (2.4V/4mA).
FREQUENCY ACCURACY AND POWER SUPPLY NOISE
The frequency accuracy of the LTC6905 may be affected
when its power supply generates noise with frequency
contents equal to fMO/64 or its multiples. fMO is the
highest frequency for an LTC6905-XXX which is with
DIV = V+ (÷1). This is also the frequency indicated in the
part number (i.e., LTC6905-100, fMO = 100MHz). fMO/64
is the master oscillator control loop frequency. For ex-
ample, if the LTC6905-80 with a master oscillator fre-
quency of 80MHz is powered by a switching regulator,
then the oscillator frequency may show an additional
error if the switching frequency is 1.4MHz (80MHz/64).
The magnitude of this effect is heavily dependent on
supply bypass and routing.
JITTER AND POWER SUPPLY NOISE
If the LTC6905 is powered by a supply that has frequency
content equal to the output frequency then the output jitter
may increase. In addition, power supply ripple in excess of
20mV at any frequency may increase jitter.
Higher divide ratios will result in lower percentage jitter.
For example, jitter percentage of the LTC6905-80 operat-
ing at 20MHz is lower than for the same part operating at
80MHz. Please consult the Jitter vs Frequency graph
showing jitter at various divider ratios.
LTC6905 SUGGESTED CRITICAL COMPONENT
LAYOUT
In order to provide the specified performance, it is re-
quired that the supply bypass capacitor be placed as close
as possible to the LTC6905. The following additional rules
should be followed for best performance:
1) The bypass capacitor must be placed as close as
possible to the LTC6905, and no vias should be placed
between the capacitor and the LTC6905. The bypass
capacitor must be on the same side of the circuit board
as the LTC6905.
2) If a ground plane is used, the connection of the LTC6905
to the ground plane should be as close as possible to the
LTC6905 GND pin and should be composed of multiple,
high current capacity vias.
Figure 2. LTC6905 Suggested Critical Component Layout
LTC6905
6905x F02
C
LTC6905-XXX Series
7
6905xfa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PACKAGE DESCRIPTIO
U
S5 Package
5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.30 – 0.45 TYP
5 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3)
S5 TSOT-23 0302
PIN ONE
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 – 0.90
1.00 MAX
0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3.85 MAX
0.62
MAX
0.95
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
LTC6905-XXX Series
8
6905xfa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2005
LT/LT 1005 REV A • PRINTED IN USA
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LTC1799 1kHz to 33MHz ThinSOT Oscillator Single Output, High Frequency Operation
LTC6900 1kHz to 20MHz ThinSOT Oscillator Single Output Lower Power
LTC6902 Multiphase Oscillator with Spread Spectrum Modulation 2-, 3- or 4-Phase Outputs
LTC6903/LTC6904 1kHz to 68MHz Serial Port Programmable Oscillator 3-Wire or I
2
CTM Programmable
LTC6905 17MHz to 170MHz Resistor Set ThinSOT Oscillator Single Resistor Sets Frequency
LTC6906 Micropower, 10kHz to 1MHz Resistor Set ThinSOT Oscillator Ultralow Power, Resistor Sets Frequency
TYPICAL APPLICATIO S
U
Driving a 50Ω Cable with the LTC6905
V+
1
2
3
5950Ω
50Ω
50Ω
CABLE
3V
3V
0.1µF
6905x TA02
4
GND
LTC6905-XXX
OE
OUT
DIV
VOUT
20
Driving the DIV Pin Without Three-State Buffers
V+
1
2
A
B
3
5
3V
3V
3V
0.1µF
6905x TA04
4
10k
10k
GND
LTC6905-XXX
OE
OUT
DIV
A
0
0
1
1
B
0
1
0
1
DIV
÷ 1
÷ 2
÷ 2
÷ 4
