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LTC6905-XXX Series Fixed Frequency SOT-23 Oscillator
FEATURES

DESCRIPTIO
No External Components to Set Frequency Frequency Error 0.5% Typical Fast Start-Up Time: 100s Typical 20ppm/C Temperature Stability Output Enable Provided Includes Divide by 1, 2 or 4 Rise Time: 0.5ns, CL = 5pF Timing Jitter: <0.8% Typical 50% 2.5% Duty Cycle IS = 8mA Typical (fOSC = 100MHz, CL = 5pF) CMOS Output Drives 600 Load Single Supply 2.7V to 5.5V Low Profile (1mm) ThinSOTTM Package
The LTC(R)6905-XXX series of parts 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 components. 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: fOSC = 133MHz, 66.7MHz, 33.3MHz LTC6905-100: fOSC = 100MHz, 50MHz, 25MHz LTC6905-96: fOSC = 96MHz, 48MHz, 24MHz LTC6905-80: fOSC = 80MHz, 40MHz, 20MHz The LTC6905-XXX series of parts are designed with 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.
APPLICATIO S

Data Clocks for High Reliability Applications High Vibration, High Acceleration Environments Replacement for Fixed Crystal and Ceramic Oscillators
, LTC and LT are registered trademarks of Linear Technology Corporation. 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.
TYPICAL APPLICATIO
Typical Distribution of Frequency Error, TA = 25C
40 VS = 3V
Basic Connection
fOSC = 133MHz
UNITS 30
3V 0.1F
1 2 3
OUT V+ LTC6905-133 GND OE DIV
6905x TA01
5
20
3V /1 4 /4 /2 OPEN
10
0 -1 -0.5 0.0 0.5 % FREQUENCY ERROR 1
6905x TA02
U
6905xf
U
U
1
LTC6905-XXX Series
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW V+ 1 GND 2 OE 3 4 DIV 5 OUT
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 .......................................... - 40C to 85C LTC6905I ............................................ - 40C to 85C LTC6905H ........................................ - 40C to 125C Specified Temperature Range (Note 8) LTC6905C ............................................... 0C to 70C LTC6905I ............................................ - 40C to 85C LTC6905H ........................................ - 40C to 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
S5 PACKAGE 5-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 150C/W
ORDER PART NUMBER LTC6905CS5-133 LTC6905IS5-133 LTC6905HS5-133 LTC6905CS5-100 LTC6905IS5-100 LTC6905HS5-100 LTC6905CS5-96 LTC6905IS5-96 LTC6905HS5-96 LTC6905CS5-80 LTC6905IS5-80 LTC6905HS5-80
S5 PART MARKING* LTBPM
LTBPK
LTBPJ
LTBPH
*The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL f PARAMETER Frequency Accuracy (Notes 2, 7)
The denotes the specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25C 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.
CONDITIONS LTC6905C-XXX TA = 25C, V+ = 3V 0C < TA < 70C LTC6905I-XXX 25C < TA < 85C - 40C < TA < 85C LTC6905H-XXX 25C < TA < 125C - 40C < TA < 125C V+ = 5V MIN TYP 0.5
MAX 1.0 1.5 1.8 2.9 2.3 2.9
UNITS % % % % % % % ppm/C %/V % ppm/kHr
1.5
f/T f/V
Freq Drift Over Temp (Note 2) Freq Drift Over Supply (Notes 2, 7) Timing Jitter (Note 3) Long-Term Stability of Output Frequency Duty Cycle V+ = 2.7V to 3.6V
20 0.5 0.8 300

47.5 2.7
50
52.5 5.5
V+
Operating Supply Range
2
U
% V
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U
WW
W
LTC6905-XXX Series
ELECTRICAL CHARACTERISTICS
SYMBOL IS PARAMETER Power Supply Current
The denotes the specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25C 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.
CONDITIONS DIV = V+ (/ 1), V+ = 3.6V LTC6905-133 LTC6905-100 LTC6905-96 LTC6905-80 DIV = 0 (/ 4), V+ = 3.6V LTC6905-133 LTC6905-100 LTC6905-96 LTC6905-80
V+ - 0.15
MIN
TYP 10 8 8 7 5 4 4 3.5
MAX 15 12 12 11 8 7 7 6 0.2
UNITS mA mA mA mA mA mA mA mA V V A A A A V V V V
VIH VIL IDIV IOE VOH
High Level DIV or OE Pins Input Voltage Low Level DIV or OE Pins Input Voltage DIV Input Current (Note 4) OE Input Current (Note 4) High Level Output Voltage (Note 4) DIV = V + DIV = 0V OE = V+ OE = 0V V + = 5.5V V + = 2.7V V+ = 5.5V V + = 5.5V

- 40
15 - 11 15 -11
40
V + = 5.5V V + = 5.5V IOH = - 1mA IOH = - 4mA IOH = - 1mA IOH = - 4mA IOL = 1mA IOL = 4mA IOL = 1mA IOL = 4mA

5.25 5.20 2.5 2.3
5.45 5.30 2.6 2.5 0.05 0.2 0.1 0.4 0.5 0.25 0.3 0.3 0.5
VOL
Low Level Output Voltage (Note 4)
V + = 5.5V V + = 2.7V
V V V V ns
tr, tf
OUT Rise/Fall Time (Note 5)
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 0C to 70C. The LTC6905C-XXX is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LTC6905I-XXX is guaranteed to meet specified performance from -40C to 85C.
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LTC6905-XXX Series TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Frequency
18 16
SUPPLY CURRENT (mA)
5.5V 2.7V
12 10 8 6 4 2 0 /4 /4 /2 /2
/1
FREQUENCY ERROR (%)
14
0
50
FREQUENCY (MHz)
6905x G01
ROUT vs V+
45 40
1.00 1.20
OUTPUT RESISTANCE ()
/1
PERCENTAGE ERROR (%)
35 30 25 20 15 10
0.20 0.80
JITTER (%)
5 0 2.5 3 3.5 4 4.5 SUPPLY VOLTAGE (V) 5 5.5
0 0 20 40 60 80 100 120 140 160 180 FREQUENCY (MHz)
6905x G05
LTC6905-80 Output Operating at 20MHz, VS = 3V
0.75V/DIV
4
UW
/1 100
6905x G04
Frequency Error vs Supply Voltage
2.50 2.00 LTC6905-133 1.50 1.00 0.50 O -0.50 LTC6905-100 LTC6905-96 LTC6905-80 2.5 3 3.5 4 4.5 SUPPLY VOLTAGE (V) 5 5.5
6905x G09
150
200
Jitter vs Frequency
1.0 0.8
/4 /2
Frequency vs Temperature
0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
6905x G08
0.60 0.40
LTC6905-133 Output Operating at 133MHz, VS = 3V
0.75V/DIV
10ns/DIV
6905x G06
2.5ns/DIV
6905x G07
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LTC6905-XXX Series
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 0.1F 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. Floating 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 15A. Likewise, driving DIV low requires sinking 15A. 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 coupling from other PCB traces. OUT (Pin 5): Oscillator Output. This pin can drive 5k and/or 5pF loads. For heavier loads, refer to the Applications Information section.
BLOCK DIAGRA
1
V+
RSET
+ -
2 GND
-
VBIAS IRES
+
GND
Table 1. LTC6905-XXX Frequency Settings DIV SETTING V+ OPEN GND LTC6905-133 133.33MHz 66.66MHz 33.33MHz LTC6905-100 100MHz 50MHz 25MHz LTC6905-96 96MHz 48MHz 24MHz LTC6905-80 80MHz 40MHz 20MHz
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3 VRES = 1V 5% (V+ - VSET) OE PROGRAMMABLE DIVIDER (N = 1, 2 OR 4) MASTER OSCILLATOR DIVIDER SELECT fMO THREE-STATE INPUT DETECT V+ 15A DIV 4 fOSC = fMO
N
OUT
5
+
IRES GAIN = 1
-
15A
6905x BD
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LTC6905-XXX Series
APPLICATIO S I FOR ATIO
START-UP TIME
The start-up and settling time to within 1% of the final frequency is typically 100s. MAXIMUM OUTPUT LOAD The LTC6905 output (Pin 5) can drive a capacitive load (CLOAD) of 5pF or more. Performance driving a CLOAD greater than 5pF depends on the oscillator's frequency (fOSC) and output resistance (ROUT). The output rise time or fall time due to ROUT and CLOAD is equal to 2.2 * ROUT * CLOAD (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/ fOSC), then the maximum output CLOAD in picofarads (pF) should be equal to or less than [45454/(ROUT * fOSC)] (ROUT in ohms and fOSC in MHz). Example: An LTC6905-100 is operating with a 3V power supply and is set for a fOSC = 50MHz. ROUT with V+ = 3V is 27 (using the ROUT vs V+ graph in the Typical Performance Characteristics). The maximum output CLOAD 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 Electrical 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 600 (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 example, if the LTC6905-80 with a master oscillator frequency of 80MHz is powered by a switching regulator,
6
U
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 operating 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 required 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.
C LTC6905
6905x F02
W
UU
Figure 2. LTC6905 Suggested Critical Component Layout
6905xf
LTC6905-XXX Series
PACKAGE DESCRIPTIO U
S5 Package 5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 2.80 BSC 1.50 - 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 - 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 - 0.90 0.20 BSC 1.00 MAX DATUM `A' 0.01 - 0.10 1.90 BSC
S5 TSOT-23 0302
3.85 MAX 2.62 REF
0.30 - 0.50 REF 0.09 - 0.20 (NOTE 3) 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
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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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7
LTC6905-XXX Series
TYPICAL APPLICATIO S
Driving a 50 Cable with the LTC6905
50 CABLE
RELATED PARTS
PART NUMBER LTC1799 LTC6900 LTC6902 LTC6903/LTC6904 LTC6905 LTC6906 DESCRIPTION 1kHz to 33MHz ThinSOT Oscillator 1kHz to 20MHz ThinSOT Oscillator Multiphase Oscillator with Spread Spectrum Modulation 1kHz to 68MHz Serial Port Programmable Oscillator 17MHz to 170MHz Resistor Set ThinSOT Oscillator Micropower, 10kHz to 1MHz Resistor Set ThinSOT Oscillator COMMENTS Single Output, High Frequency Operation Single Output Lower Power 2-, 3- or 4-Phase Outputs 3-Wire or I2CTM Programmable Single Resistor Sets Frequency Ultralow Power, Resistor Sets Frequency
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
A B
3V 0.1F
1 2 3
V+ OUT LTC6905-XXX GND OE DIV
5
950
VOUT 20 50
3V
4
6905x TA02
Driving the DIV Pin Without Three-State Buffers
A 0 0 1 1 B 0 1 0 1 3V 3V 10k
6905x TA04
DIV /1 /2 /2 /4
3V 0.1F
1 2 3
V+ OUT LTC6905-XXX GND OE DIV
5
4
10k
6905xf LT/TP 0205 1K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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