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LTC6930-X.XX 32.768kHz to 8.192MHz Precision Power Oscillators FEATURES
n n n n n n n n
DESCRIPTION
The LTC(R)6930 series is a family of very low power precision silicon oscillators with a frequency error less than 0.09%. For each oscillator, the user can select one of 8 frequencies between 32.768kHz and 8.192MHz. Based on a fixed master oscillator frequency, internal frequency dividers between 1 and 128 provide the 8 different frequencies. The LTC6930 requires no external components other than power supply bypass capacitors. Requiring only a single 1.7V to 5.5V supply enables operation from a single Li-Ion cell or 2 AA alkaline cells. The LTC6930 features a proprietary control architecture that allows for ultra-low power operation while maintaining industry leading accuracy and jitter specifications. The exceptionally fast start-up time, combined with the low power consumption, is ideal for battery operated applications with frequent power-up cycles. Any frequency from 32.768kHz to 8.192MHz can be provided by the factory. Minimum order sizes apply for custom frequencies. Please consult LTC Marketing for details.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6342817, 6614313.
n n
Frequency Error <0.09% Max at 25C Startup Time <110s at All Frequencies 1.7V to 5.5V Single Supply Operation 105A Typical Supply Current at 32kHz, V+ = 3V 490A Typical Supply Current at 8MHz, V+ = 3V Typical RMS Period Jitter <0.15% at V+ = 3V No External Components to Set Frequency 5 Options Cover 32.768kHz to 8.192MHz: LTC6930-4.19: 4.194304MHz / N LTC6930-5.00: 5.000000MHz / N LTC6930-7.37: 7.373800MHz / N LTC6930-8.00: 8.000000MHz / N LTC6930-8.19: 8.192000MHz / N Where N = 1, 2, 4, 8, 16, 32, 64, 128 (N Determined by State of DIVA, DIVB, DIVC Pins) -40C to 125C Operating Temperature Range Tiny 2mm x 3mm DFN or MS8 Package
APPLICATIONS
n n n n
Digitally Controlled Oscillator Microprocessor Clock Power Supply Clock Portable and Battery Operated Devices
TYPICAL APPLICATION
4MHz Micropower Clock Generator
V+ = 1.7V TO 5.5V IS = 325A AT 3VDC
Typical Frequency Error Distribution
70 TA = 25C V+ = 3V 60 DIV = 0 1045 UNITS 50 UNITS 40 30 20 10 0 -0.10
0.1F V+ V+
DIVA OUT LTC6930-8.00 DIVB DIVC GND GND
4MHz
6930 TA01a
-0.05 0 0.05 FREQUENCY ERROR (%)
0.10
6930 TA01b
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LTC6930-X.XX ABSOLUTE MAXIMUM RATINGS
(Note 1)
Total Supply Voltage (V+ to GND) ............................................. -0.3V to 6V Any Input Pin to GND (DIV Pins) ......................................-0.3V to V+ + 0.3V Operating Temperature Range (Note 2) LTC6930C ............................................ -40C to 85C LTC6930I.............................................. -40C to 85C LTC6930H .......................................... -40C to 125C
Specified Temperature Range (Note 3) LTC6930C ................................................ 0C to 70C LTC6930I.............................................. -40C to 85C LTC6930H .......................................... -40C to 125C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
PIN CONFIGURATION
TOP VIEW V+ 1 GND 2 DIVA 3 DIVB 4 9 8 V+ 7 OUT 6 GND 5 DIVC TOP VIEW V+ 1 GND 2 DIVA 3 DIVB 4 8 7 6 5 V+ OUT GND DIVC
DCB PACKAGE 8-LEAD (2mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 64C/W EXPOSED PAD (PIN 9) IS V-, MUST BE SOLDERED TO PCB
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 300C/W (SINGLE-LAYER BOARD)
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI) LTC6930CDCB-4.19#TRMPBF LTC6930IDCB-4.19#TRMPBF LTC6930CDCB-5.00#TRMPBF LTC6930IDCB-5.00#TRMPBF LTC6930CDCB-7.37#TRMPBF LTC6930IDCB-7.37#TRMPBF LTC6930CDCB-8.00#TRMPBF LTC6930IDCB-8.00#TRMPBF LTC6930CDCB-8.19#TRMPBF LTC6930IDCB-8.19#TRMPBF TRM = 500 pieces.
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TAPE AND REEL LTC6930IDCB-4.19#TRPBF
PART MARKING* PACKAGE DESCRIPTION LCKT
TEMPERATURE RANGE
LTC6930CDCB-4.19#TRPBF LCKT
8-Lead (2mm x 3mm) Plastic DFN 0C to 70C 8-Lead (2mm x 3mm) Plastic DFN -40C to 85C 8-Lead (2mm x 3mm) Plastic DFN -40C to 125C 8-Lead (2mm x 3mm) Plastic DFN 0C to 70C 8-Lead (2mm x 3mm) Plastic DFN -40C to 85C 8-Lead (2mm x 3mm) Plastic DFN -40C to 125C 8-Lead (2mm x 3mm) Plastic DFN 0C to 70C 8-Lead (2mm x 3mm) Plastic DFN -40C to 85C 8-Lead (2mm x 3mm) Plastic DFN -40C to 125C 8-Lead (2mm x 3mm) Plastic DFN 0C to 70C 8-Lead (2mm x 3mm) Plastic DFN -40C to 85C 8-Lead (2mm x 3mm) Plastic DFN -40C to 125C 8-Lead (2mm x 3mm) Plastic DFN 0C to 70C 8-Lead (2mm x 3mm) Plastic DFN -40C to 85C 8-Lead (2mm x 3mm) Plastic DFN -40C to 125C
LTC6930HDCB-4.19#TRMPBF LTC6930HDCB-4.19#TRPBF LCKT LTC6930CDCB-5.00#TRPBF LCKV LTC6930IDCB-5.00#TRPBF LCKV
LTC6930HDCB-5.00#TRMPBF LTC6930HDCB-5.00#TRPBF LCKV LTC6930CDCB-7.37#TRPBF LCKW LTC6930IDCB-7.37#TRPBF LCKW
LTC6930HDCB-7.37#TRMPBF LTC6930HDCB-7.37#TRPBF LCKW LTC6930CDCB-8.00#TRPBF LCKX LTC6930IDCB-8.00#TRPBF LCKX
LTC6930HDCB-8.00#TRMPBF LTC6930HDCB-8.00#TRPBF LCKX LTC6930CDCB-8.19#TRPBF LCKY LTC6930IDCB-8.19#TRPBF LCKY
LTC6930HDCB-8.19#TRMPBF LTC6930HDCB-8.19#TRPBF LCKY
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LTC6930-X.XX ORDER INFORMATION
LEAD FREE FINISH LTC6930IMS8-4.19#PBF LTC6930HMS8-4.19#PBF LTC6930CMS8-5.00#PBF LTC6930IMS8-5.00#PBF LTC6930HMS8-5.00#PBF LTC6930CMS8-7.37#PBF LTC6930IMS8-7.37#PBF LTC6930HMS8-7.37#PBF LTC6930CMS8-8.00#PBF LTC6930IMS8-8.00#PBF LTC6930HMS8-8.00#PBF LTC6930CMS8-8.19#PBF LTC6930IMS8-8.19#PBF TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP TEMPERATURE RANGE -40C to 85C -40C to 125C 0C to 70C -40C to 85C -40C to 125C 0C to 70C -40C to 85C -40C to 125C 0C to 70C -40C to 85C -40C to 125C 0C to 70C -40C to 85C -40C to 125C LTC6930IMS8-4.19#TRPBF LTCKZ LTC6930HMS8-4.19#TRPBF LTCKZ LTC6930CMS8-5.00#TRPBF LTCLB LTC6930IMS8-5.00#TRPBF LTCLB LTC6930HMS8-5.00#TRPBF LTCLB LTC6930CMS8-7.37#TRPBF LTCLC LTC6930IMS8-7.37#TRPBF LTCLC LTC6930HMS8-7.37#TRPBF LTCLC LTC6930CMS8-8.00#TRPBF LTCLD LTC6930IMS8-8.00#TRPBF LTCLD LTC6930HMS8-8.00#TRPBF LTCLD LTC6930CMS8-8.19#TRPBF LTCLF LTC6930IMS8-8.19#TRPBF LTCLF
LTC6930HMS8-8.19#PBF LTC6930HMS8-8.19#TRPBF LTCLF 8-Lead Plastic MSOP *Temperature grades are identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
AC ELECTRICAL CHARACTERISTICS
SYMBOL fi f PARAMETER Initial Frequency Accuracy Frequency Accuracy (Note 4) CONDITIONS
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Unless otherwise noted, specifications apply over the full range of operating supply voltage and frequency output: V+ = 1.7V to 5.5V and all DIV settings with CLOAD = 5pF RLOAD = . ,
MIN TYP 0.08
l l l l l l l l l l l l l
MAX 0.09 0.45 0.65 1 0.52 0.65 1.1 0.8 0.95 1.3
UNITS % % % % % % % % % % %/C %/C %/V ppm/kHr
DIVA = DIVB = DIVC = 0, TA = 25C, V+ = 3V V+ = 3V - 3.6V LTC6930C LTC6930I LTC6930H V+ = 2V - 3.6V LTC6930C LTC6930I LTC6930H V+ = 1.7V - 5.5V LTC6930C LTC6930I LTC6930H
0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.0001 0.001 0.07 30
f/T f/V
Frequency Drift Over Temperature Frequency Drift Over Supply Long-Term Frequency Stability
MS8 Package DCB Package (Note 5)
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LTC6930-X.XX AC ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER RMS Period Jitter CONDITIONS DIVA = DIVB = DIVC = 0, V+ = 3V LTC6930-4.19 (4.194304MHz) LTC6930-5.00 (5.000000MHz) LTC6930-7.37 (7.372800MHz) LTC6930-8.00 (8.000000MHz) LTC6930-8.19 (8.192000MHz)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Unless otherwise noted, specifications apply over the full range of operating supply voltage and frequency output: V+ = 1.7V to 5.5V and all DIV settings with CLOAD = 5pF RLOAD = . ,
MIN TYP 320 1.7 225 1.2 180 0.97 130 0.8 130 0.8 MAX UNITS ps RMS nsP-P ps RMS nsP-P ps RMS nsP-P ps RMS nsP-P ps RMS nsP-P
DC ELECTRICAL CHARACTERISTICS
SYMBOL VS IS,DC PARAMETER Supply Voltage Applied Between V+ and GND V+ Combined Supply Current CONDITIONS
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Unless otherwise noted, specifications apply over the full range of operating supply voltage and frequency output: V+ = 1.7V to 5.5V and all DIV settings with CLOAD = 5pF RLOAD = . ,
l
MIN 1.7
TYP
MAX 5.5
UNITS V
LTC6930-4.19 DIVA = DIVB = DIVC = 0, V+ = 1.7V DIVA = DIVB = DIVC = 0, V+ = 3V DIVA = DIVB = DIVC = 0, V+ = 5.5V DIVA = DIVB = DIVC = 1, V+ = 1.7V DIVA = DIVB = DIVC = 1, V+ = 3V DIVA = DIVB = DIVC = 1, V+ = 5.5V LTC6930-5.00 DIVA = DIVB = DIVC = 0, V+ = 1.7V DIVA = DIVB = DIVC = 0, V+ = 3V DIVA = DIVB = DIVC = 0, V+ = 5.5V DIVA = DIVB = DIVC = 1, V+ = 1.7V DIVA = DIVB = DIVC = 1, V+ = 3V DIVA = DIVB = DIVC = 1, V+ = 5.5V
l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l
170 260 490 80 105 130 201 307 579 95 124 154 296 453 853 139 183 226 321 491 926 151 198 246 310 500 880 150 190 210 1.25
290 420 750 160 190 355 430 570 960 176 212 375 480 660 1310 220 273 440 520 740 1380 240 295 475 490 760 1400 270 325 540 1.4
A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A V
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IS,DC
V+ Combined Supply Current
LTC6930-7.37 DIVA = DIVB = DIVC = 0, V+ = 1.7V DIVA = DIVB = DIVC = 0, V+ = 3V DIVA = DIVB = DIVC = 0, V+ = 5.5V DIVA = DIVB = DIVC = 1, V+ = 1.7V DIVA = DIVB = DIVC = 1, V+ = 3V DIVA = DIVB = DIVC = 1, V+ = 5.5V LTC6930-8.00 DIVA = DIVB = DIVC = 0, V+ = 1.7V DIVA = DIVB = DIVC = 0, V+ = 3V DIVA = DIVB = DIVC = 0, V+ = 5.5V DIVA = DIVB = DIVC = 1, V+ = 1.7V DIVA = DIVB = DIVC = 1, V+ = 3V DIVA = DIVB = DIVC = 1, V+ = 5.5V LTC6930-8.19 DIVA = DIVB = DIVC = 0, V+ = 1.7V DIVA = DIVB = DIVC = 0, V+ = 3V DIVA = DIVB = DIVC = 0, V+ = 5.5V DIVA = DIVB = DIVC = 1, V+ = 1.7V DIVA = DIVB = DIVC = 1, V+ = 3V DIVA = DIVB = DIVC = 1, V+ = 5.5V
VIH
Minimum High Level Input Voltage, All Digital Input Pins
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LTC6930-X.XX DC ELECTRICAL CHARACTERISTICS
SYMBOL VIL IIN ROUT VOH PARAMETER Maximum Low Level Input Voltage, All Digital Input Pins Digital Input Leakage Current, All Digital Input Pins Output Resistance High Level Output Voltage CONDITIONS
l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Unless otherwise noted, specifications apply over the full range of operating supply voltage and frequency output: V+ = 1.7V to 5.5V and all DIV settings with CLOAD = 5pF RLOAD = . ,
MIN 0.7 TYP 1.25 MAX UNITS V A V V V V V V V V 0.1 0.1 0.1 V V V V V V V V
0 < VIN < V+ OUT Pin, V+ = 3V DIVA = DIVB = DIVC = 0, No Load V+ = 5.5V V+ = 3V V+ = 2V V+ = 1.7V DIVA = DIVB = DIVC = 0, 1k Load to GND V+ = 5.5V V+ = 3V V+ = 2V V+ = 1.7V DIVA = DIVB = DIVC = 0, No Load V+ = 5.5V V+ = 3V V+ = 2V V+ = 1.7V DIVA = DIVB = DIVC = 0, 1k Load to V+ V+ = 5.5V V+ = 3V V+ = 2V V+ = 1.7V
l
1 40
l l l
5.4 2.9 1.8
5.5 3 2 1.7 5.2 2.7 1.6 1.5 0 0 0 0 0.3 0.3 0.3 0.3
l l l
5 2.6 1.5
VOL
Low Level Output Voltage
l l l
l l l
0.7 0.5 0.35
TIMING CHARACTERISTICS
SYMBOL trf DCY PARAMETER Output Rise/Fall Time (10% to 90%) Duty Cycle
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Unless otherwise noted, specifications apply over the full range of operating supply voltage and frequency output: V+ = 1.7V to 5.5V and fOUT = 32.768kHz to 8.192MHz with CLOAD = 5pF RLOAD = . ,
CONDITIONS V+ = 3V DIVA = DIVB = DIVC = 0; V+ = 2V to 5.5V DIVA = DIVB = DIVC = 0 DIVA or DIVB or DIVC 0
l l l l
MIN 35 35 48
TYP 3 50 50 50 1
MAX 65 70 52 110
UNITS ns % % % Cycle s
DDIV DPON
DIV to FOUT Delay Power On Delay
Edge of DIV Signal to 1st Accurate Output Cycle V+ > 1.7V to 1st Accurate Output Cycle
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: LTC6930C is guaranteed functional over the operating range of -40C to 85C. Note 3: The LTC6930C is guaranteed to meet specified performance from 0C to 70C. The LTC6930C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LTC6930I is guaranteed to meet specified performance from -40C to 85C. The LTC6930H is guaranteed to meet specified performance from -40C to 125C. Note 4: Frequency accuracy and frequency drift are defined as deviation from the nominal frequency or the nominal frequency divided by the integer set through the DIV pins for each part. The nominal frequency for
the LTC6930 family of parts are defined as follows: LTC6930-4.19 fNOM = 4.194304MHz LTC6930-5.00 fNOM = 5.000000MHz LTC6930-7.37 fNOM = 7.372800MHz LTC6930-8.00 fNOM = 8.000000MHz LTC6930-8.19 fNOM = 8.192000MHz Note 5: Long-term drift of silicon oscillators is primarily due to the movement of ions and impurities within the silicon and is tested at 30C under otherwise nominal operating conditions. Long-term drift is specified as ppm/kHr due to the typically non-linear nature of the drift. To calculate drift for a set time period, translate that time into thousands of hours, take the square root and multiply by the typical drift number. For instance, a year is 8.77kHr and would yield a drift of 89ppm at 30ppm/kHr. Drift without power applied to the device may be approximated as 1/10th of the drift with power, or 3ppm/kHr for a 30ppm/kHr device.
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LTC6930-X.XX TYPICAL PERFORMANCE CHARACTERISTICS
Typical Frequency Error vs Supply Voltage
FREQUENCY ERROR (%, NORMALIZED TO 3V) 0.25 0.20 FREQUENCY ERROR (%) 8.19MHz FREQUENCY ERROR (%) 0.15 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 -0.25 1.7 2.7 3.7 4.7 SUPPLY VOLTAGE (V)
4216 G01
Frequency Error vs Temperature, MS8 Package
0.60 0.40 0.20 0 -0.20 -0.40 -0.60 -45 -25 -5 V+ = 3V 0.60 0.40 0.20 0 -0.20 -0.40
Frequency Error vs Temperature, DFN Package
V+ = 3V
TA = 25C
4.19MHz
15 35 55 75 TEMPERATURE (C)
95 115 125
4216 G02
-0.60 -45 -25 -5
15 35 55 75 TEMPERATURE (C)
95 115 125
4216 G03
Typical Supply Current vs DIV Setting
600 500 SUPPLY CURRENT (A) SUPPLY CURRENT (A) 400 8.192MHz, 1.7V 300 8.192MHz, 3V 200 100 4.194MHz, 3V 0 1 10 DIV SETTING (LOG) 100
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Typical Supply Current vs Load Capacitance
2000 1800 1600 1400 1200 1000 800 600 400 DIV = 1 DIV = 2 DIV = 4 DIV = 8 LTC6930-8.19 V+ = 3V TA = 25C SUPPLY CURRENT (A) DIV = 16 DIV = 32 DIV = 64 DIV = 128 1000
Typical Supply Current vs Supply Voltage
DIVIDE = 1 900 TA = 25C 800 700 600 500 400 300 200 100 4.194MHz 8.192MHz
TA = 25C
4.194MHz, 1.7V
200 0 0 10 20 30 40 50 LOAD CAPACITANCE (pF) 60
4216 G05
0 1.7
2.2
2.7 3.2 3.7 4.2 4.7 SUPPLY VOLTAGE (V)
5.2
4216 G06
Typical Supply Current vs Temperature
700 POWER SUPPLY CURRENT (A) 600 500 400 3V, 4.19MHz 300 200 100 0 -45 1.7V, 32kHz 5 55 TEMPERATURE (C) 105
4216 G07
Typical Output Spectrum, 8MHz
Typical Output Waveform, 8MHz
CLOAD = 5pF
3V, 8.192MHz 10dB/DIV 0.45V/DIV
400kHz/DIV
6930 G08
LTC6930-8.00 CLOAD = 12pF
40ns/DIV
6930 G09
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LTC6930-X.XX TYPICAL PERFORMANCE CHARACTERISTICS
Typical Jitter vs Supply in Divide by 1 Mode
0.30 0.25 4.194MHz JITTER (% RMS) 0.20 SAMPLES 0.15 8.192MHz 0.10 100 0.05 0 1.7 0 -450 200 300 JITTER (% RMS) TA = 25C 400
Typical Period Jitter Histogram
LTC6930-8.19 V+ = 3V TA = 25C DIVIDE = 1 0.16 0.14 0.12 0.10 0.08
Typical Jitter vs Divider Setting
V+ = 3V TA = 25C
4.194MHz 0.06 0.04 0.02 0 8.192MHz
2.2
2.7 3.2 3.7 4.2 4.7 SUPPLY VOLTAGE (V)
5.2
4216 G10
-300
-150 0 150 PERIOD ERROR (ps)
300
450
4216 G11
1
10 DIV SETTING (LOG)
100
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Typical Output Rise/Fall Time vs Supply
4.5 4.0 OUTPUT RISE/FALL TIME (ns) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 1.7 2.2 2.7 3.2 3.7 4.2 4.7 SUPPLY VOLTAGE (V) 5.2
4216 G13
Typical Output Resistance vs Supply Voltage
100 90 OUTPUT RESISTANCE () 80 DUTY CYCLE (%) 70 60 50 40 30 20 10 0 1.7 2.2 2.7 3.2 3.7 4.2 4.7 SUPPLY VOLTAGE (V) 5.2
4216 G14
Typical Output Duty Cycle vs Supply and Divide Ratio
60 58 56 54 52 50 48 DIVIDE BY >1 46 44 42 40 1.7 2.2 2.7 3.2 3.7 4.2 4.7 SUPPLY VOLTAGE (V) 5.2
4216 G15
CLOAD = 5pF TA = 25C
TA = 25C
8MHz, DIVIDE BY 1
RISE TIME
FALL TIME
4MHz, DIVIDE BY 1
Typical Frequency Settling from Power-Up
10 5 0 -5 -10 -15 -20 -25 -30 0 50 100 150 TIME SINCE POWER APPLIED (s) 200
4216 G16
Typical Frequency Error vs Time (Long-Term Drift)
500 25 PARTS SHOWN 400 TA = 30C DELTA FREQUENCY (ppm) 300 200 100 0 -100 -200 -300 -400 -500 0 500 1000 1500 2000 TIME (HOURS) 2500 3000
Typical Output Waveform at DIV Pin Change
FREQUENCY ERROR (%)
400ns/DIV
6930 G18
4216 G17
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LTC6930-X.XX PIN FUNCTIONS
V+ (Pins 1, 8): Positive Supply Pins. Each supply pin should be bypassed directly to the neighboring GND pin with a 0.1F ceramic capacitor, and must be externally connected to the other V+ pin (see recommended layout). GND (Pins 2, 6): Ground Pins. Each should be connected to a low inductance ground plane and must be connected to the other GND pin and on the DFN package, Pin 9. DIVA, DIVB, DIVC (Pins 3, 4, 5): Output Prescaler. Selects divide ratio of master oscillator frequency used to generate the output. See frequency setting Table 1 for function. These are standard CMOS logic inputs with a typical threshold of 1.25V OUT (Pin 7): Oscillator Output. Drives up to 50pF capacitive or 1k resistive load (Refer to Supply Current vs Load Capacitance in Typical Performance Characteristics section). Typical series resistance is less than 80 at 1.7V and less than 40 at 3V supply. The output trace should be isolated as much as possible from Pin 1 and Pin 2. The OUT pin is held low during startup, and remains free from glitches and runt pulses during DIV pin switching. Exposed Pad (Pin 9, DFN Only): The Exposed Pad must be soldered to a PCB plane connected to GND.
APPLICATIONS INFORMATION
Theory of Operation The LTC6930 is an entirely self contained all silicon oscillator which consists of a master oscillator, a control loop and an output frequency divider. The master oscillator operates between 4.2MHz and 8.2MHz and is factory programmed. The master oscillator frequency is accurately maintained over temperature and environmental extremes by a proprietary switched capacitor feedback loop. Each LTC6930 oscillator has an output frequency divider which is controlled via the DIVA, DIVB and DIVC inputs. The divider divides the master frequency by 2N, where N is an integer from 0 to 7 (divider ranges from 1 to 128). See Table 1 for the full range of frequencies covered by the LTC6930 family. The presence of two sets of supply pins and careful internal layout reduce interference between the oscillator output and the control loop. This allows the LTC6930 to provide a clean output frequency with very little deterministic jitter, even in cases of heavy output loading and noisy operating environments. The supply voltage of the LTC6930 is internally regulated to maintain a very low frequency drift over supply. Output Driver and Loading The output of the LTC6930 is a low series resistance 40 CMOS driver with controlled rise/fall times to limit RF interference and power supply spikes generated by the output while preserving the ability to drive low impedance loads. Especially at high frequencies, the capacitive loading of the output of the LTC6930 may cause the majority of the power supply dissipation of the part. The LTC6930 supply current is specified at an output load of 5pF which is equivalent to two standard HC logic inputs. , The portion of the power supply current needed to drive a capacitive load may be calculated as: ISUPPLY = CLOAD * VSWING * fOSC where CLOAD is the 5pF load capacitance, VSWING is the voltage swing, in this case up to 5.5V, and fOSC is the frequency of the oscillator output. Driving a 5.5V swing into a 5pF load at 8MHz takes an average of 220A. To calculate the portion of the supply current needed for a 50pF load, simply substitute 50pF for CLOAD in the same equation: 50pF * 5.5V * 8MHz = 2.2mA The majority of this power is expended during the rise and fall time of the output signal, not while it is in a steady
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LTC6930-X.XX APPLICATIONS INFORMATION
state. The 2ns rise and fall times of the LTC6930 mean that the instantaneous power supply current required during the rise and fall portions of the waveform is much greater than the average. The instantaneous power supply current may be calculated by a similar formula: IPEAK = CLOAD * VSWING * 1 trf Startup Time The startup time of the LTC6930 is typically 50s from the time that valid power is applied to the first output pulse. The output is held low for the first 50s to prevent any glitches, runt pulses, or invalid frequency output during startup. Long-Term Drift Long-term stability of silicon oscillators is specified in ppm/kHr, which is typical of other silicon devices such as operational amplifiers and voltage references. Because drift in silicon-based oscillators is generated primarily by movement of ions in the silicon, most of the drift is accomplished early in the life of the device and the drift can be expected to level off in the long term. The ppm/kHr unit models this time variant decay. Crystal oscillators are often specified with drift measured in ppm/year because their drift mechanism is different. A comparison of various drift rates over a five year time period is shown in Figure 2. When calculating the amount of drift to be expected, it is important to consider the entire time in the calculation, because the relationship to time is not linear. The drift for 5 years is not 5 times the drift for one year. A sample
0.045 GND 0.040 0.035 0.030 GND
6930 F01
where trf is the rise/fall time of the signal. In this case, 14mA spikes are generated by driving 5.5V into a 5pF load. Power is supplied to the output driver of the LTC6930 from the V+ and GND pins on each side of the output pin (Pins 6 and 8). Allowances must be made in the design to provide for output load related supply current spikes, especially in high accuracy applications. A 0.1F ceramic capacitor connected between V+ and GND (Pins 6 and 8) as close as possible to the device will decouple the rest of the circuit from spikes caused by powering a capacitive output load of up to 50pF See Figure 1. .
C1 0.1F
V+ OUT C2 0.1F
60ppm/kHr
DRIFT (%)
0.025 0.020 0.015 0.010 0.005 0 0 20 10ppm/kHr 40 MONTHS 60 80
6930 F02
Figure 1. Recommended Layout
30ppm/kHr
Switching the DIV Pins The LTC6930 is designed to quickly and cleanly respond to the digital inputs. The output will respond to the DIV pins within a single clock cycle without introducing any sliver or runt pulses.
Figure 2. 5 Year Drift at Various Rates
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9
LTC6930-X.XX APPLICATIONS INFORMATION
calculation for drift over 5 years at 30ppm/kHr is as follows: 5 years * 365.25 days/year * 24 hours/day = 43,830 hours = 43.830kHr 43.830kHr = 6.62kHr 6.62kHr * 30ppm/kHr = 0.0198% over 5 years. Drift calculations assume that the part is in continuous operation during the entire time period of the calculation. The movement of ions which results in drift is usually aided by electric fields in the operating parts, and the typical drift spec applies while the part is powered up. Conservative calculations would use a tenth of the drift specification for time when power is not applied to the part.
Table 1. Frequency Setting and Available Frequencies
/1 DIV Pin Settings [DIVC][DIVB][DIVA] LTC6930-4.19 LTC6930-5.00 LTC6930-7.37 LTC6930-8.00 LTC6930-8.19 000 5.000MHz 7.3728MHz 8.000MHz 8.192MHz /2 001 2.500MHz 3.6864MHz 4.000MHz 4.096MHz /4 010 1.250MHz 1.8432MHz 2.000MHz 2.048MHz /8 011 524.288kHz 625.0kHz 921.6kHz 1000kHz 1024kHz /16 100 262.144kHz 312.5kHz 460.8kHz 500.0kHz 512.0kHz /32 101 131.072kHz 156.25kHz 230.4kHz 250.0kHz 256.0kHz /64 110 65.536kHz 78.125kHz 115.2kHz 125.0kHz 128.0kHz /128 111 32.768kHz 39.0625kHz 57.6kHz 62.5kHz 64.0kHz
Setting the Frequency The output frequency of the LTC6930 is chosen from the values in Table 1 and set using the DIV pins, as noted in the table. Master oscillator frequency is preset in the factory, and the DIV pins select an internal binary divider of up to 128. For example, if the desired oscillator output frequency is 2.5MHz, finding 2.5MHz in Table 1 shows that the LTC6930-5.00 should be ordered, having a master oscillator frequency of 5MHz, and a DIV value of [001] should be used. This would equate to grounding DIVC and DIVB, while connecting DIVA to the positive supply. Frequencies other than those shown in Table 1 may be requested.
4.194304MHz 2.097152MHz 1.048576MHz
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10
LTC6930-X.XX PACKAGE DESCRIPTION
DCB Package 8-Lead Plastic DFN (2mm x 3mm)
(Reference LTC DWG # 05-08-1718 Rev A)
2.00 0.10 (2 SIDES) 0.70 0.05 1.35 0.05 1.65 0.05 3.00 0.10 (2 SIDES) PACKAGE OUTLINE PIN 1 BAR TOP MARK (SEE NOTE 6) 4 0.25 0.05 0.45 BSC 1.35 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.00 - 0.05 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.200 REF 0.75 0.05 1.35 REF BOTTOM VIEW--EXPOSED PAD 1 R = 0.115 TYP R = 0.05 5 TYP 0.40 0.10 8
3.50 0.05 2.10 0.05
1.35 0.10 1.65 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 x 45 CHAMFER
(DCB8) DFN 0106 REV A
0.23 0.05 0.45 BSC
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660 Rev F)
0.889 0.127 (.035 .005) 3.00 0.102 (.118 .004) (NOTE 3) 0.52 (.0205) REF
8
7 65
5.23 (.206) MIN
3.20 - 3.45 (.126 - .136)
0.254 (.010)
DETAIL "A" 0 - 6 TYP
4.90 0.152 (.193 .006)
3.00 0.102 (.118 .004) (NOTE 4)
GAUGE PLANE
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
DETAIL "A" 0.18 (.007)
1 0.53 0.152 (.021 .006) 1.10 (.043) MAX
23
4 0.86 (.034) REF
RECOMMENDED SOLDER PAD LAYOUT
SEATING PLANE NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.22 - 0.38 (.009 - .015) TYP
0.65 (.0256) BSC
0.1016 0.0508 (.004 .002)
MSOP (MS8) 0307 REV F
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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.
11
LTC6930-X.XX TYPICAL APPLICATION
Dual, Matched, Digitally Programmable, Lowpass Filter, 2kHz to 256kHz
5V 3.48k 3 2k 1F 4 V VIN1 1 2 IN+ IN- GND
-
OUT V+ RX DIV/CLK
8 7 6 5
VOUT1 5V 0.1F
LTC1569-7 0
Amplitude Response
5V 3.48k
VIN2
1 2 3
IN+ IN- GND V-
OUT V+ RX DIV/CLK
8 7 6 5
VOUT2 GAIN (dB) 5V 0.1F
-20
-40 fCUTOFF = 8kHz
32kHz 128kHz
2k
1F 4
LTC1569-7
-60
1 0.1F 2 3 4
V+ GND DIVA DIVB
V+ OUT GND DIVC
8 7 6 5
5V 0.1F fOSC
-80
-100
1
10 100 FREQUENCY (kHz)
1000
DIVA DIVB DIVC
LTC6930-8.192
6930 TA02
DIVC, DIVB, DIVA fCUTOFF
000 256kHz
001 128kHz
010 64kHz
011 32kHz
100 16kHz
101 8kHz
110 4kHz
111 2kHz
RELATED PARTS
PART NUMBER LTC1799 LTC6900 LTC6902 LTC6903/LTC6904 LTC6905 LTC6905-XXX LTC6906 LTC6907 LTC6908 DESCRIPTION 1kHz to 33MHz ThinSOT Oscillator, Resistor Set 1kHz to 20MHz ThinSOT Oscillator, Resistor Set Multiphase Oscillator with Spread Spectrum Modulation 1kHz to 68MHz Serial Port Programmable Oscillator 17MHz to 170MHz ThinSOT Oscillator, Resistor Set Fixed Frequency ThinSOT Oscillator Family, up to 133MHz Micropower 10kHz to 1MHz ThinSOT Oscillator, Resistor Set Micropower 40kHz to 4MHz ThinSOT Oscillator, Resistor Set Multiphase Oscillator with Spread Spectrum Modulation COMMENTS Wide Frequency Range Low Power, Wide Frequency Range 2-, 3- or 4-Phase Outputs 0.1% Frequency Resolution, I2C or SPI Interface High Frequency, 100sec Startup, 7ps RMS Jitter No Trim Components Required 12A Supply Current at 100kHz, 0.65% Frequency Accuracy 36A Supply Current at 400kHz, 0.65% Frequency Accuracy 2 Outputs Shifted by Either 180 or 90
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12 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0708 REV A * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2008

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