Datasheet LTC6902 (Analog Devices)
| 制造商 | Analog Devices |
| 描述 | Multiphase Oscillator with Spread Spectrum Frequency Modulation |
| 页数 / 页 | 16 / 1 — FEATURES. DESCRIPTIO. 2-, 3- or 4-Phase Outputs. Optional Spread Spectrum … |
| 文件格式/大小 | PDF / 213 Kb |
| 文件语言 | 英语 |
FEATURES. DESCRIPTIO. 2-, 3- or 4-Phase Outputs. Optional Spread Spectrum Frequency Modulation. for Improved EMC Performance
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LTC6902 Multiphase Oscillator with Spread Spectrum Frequency Modulation
U FEATURES DESCRIPTIO
■
2-, 3- or 4-Phase Outputs
The LTC®6902 is a precision, low power and easy-to-use ■
Optional Spread Spectrum Frequency Modulation
oscillator that provides multiphase outputs in a small
for Improved EMC Performance
package. The oscillator frequency is set by a single exter- ■
5kHz to 20MHz Frequency Range
nal resistor (RSET). The LTC6902 also provides an optional ■ One External Resistor Sets the Frequency spread spectrum frequency modulation (SSFM) capability ■ One External Resistor Sets Percent Frequency that can be activated and controlled by an additional Spreading external resistor (RMOD). ■ 400µA Typical Supply Current, VS = 3V, 1MHz The LTC6902’s master oscillator is controlled by the RSET ■ Frequency Error ≤1.5% Max, 5kHz to 10MHz resistor and has a range of 100kHz and 20MHz. In order (TA = 25°C) to accommodate a wider output frequency range, a pro- ■ Frequency Error ≤ 2% Max, 5kHz to 10MHz grammable divider (divide by 1, 10 or 100) is included. (TA = 0°C to 70°C) The integrated programmable multiphase circuit pro- ■ ±40ppm/°C Temperature Stability vides either 2-, 3- or 4-phase waveforms. ■ Fast Start-Up Time: 50µs to 1.5ms ■ 100Ω CMOS Output Driver The LTC6902’s SSFM capability modulates the oscillator’s ■ Operates from a Single 2.7V to 5.5V Supply frequency by a pseudorandom noise (PRN) signal to ■ Available in 10-Lead MS Package spread the oscillator’s energy over a wide frequency band. This spreading decreases the peak electromagnetic radia-
U APPLICATIO S
tion level and improves electromagnetic compatibility (EMC) performance. The amount of frequency spreading ■ Switching Power Supply Clock Reference is programmable by a single additional external resistor ■ Portable and Battery-Powered Equipment (RMOD) and is disabled by grounding the MOD pin. ■ PDAs , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Cell Phones ■ Clocking Switched Capacitor Filters
U TYPICAL APPLICATIO Output Frequency Spectrum With and Without SSFM 500kHz, 4-Phase Clock with 20% Frequency Spreading
0 OUTPUT SPECTRUM 5V R WITH SSFM MOD 10k –20 0.1µF DISABLED R OUTPUT SET 10k SPECTRUM –40 WITH 20% LTC6902 SPREADING V+ SET –60 OPEN DIV MOD PH GND OUT1 OUT4 OUT4 RELATIVE AMPLITUDE (dBm) –80 OUT2 OUT3 OUT3 OUT2 –100 OUT1 400 450 500 550 600 6902 TA01 FREQUENCY (kHz) 6902 TA02 6902f 1
U FEATURES DESCRIPTIO
■
2-, 3- or 4-Phase Outputs
The LTC®6902 is a precision, low power and easy-to-use ■
Optional Spread Spectrum Frequency Modulation
oscillator that provides multiphase outputs in a small
for Improved EMC Performance
package. The oscillator frequency is set by a single exter- ■
5kHz to 20MHz Frequency Range
nal resistor (RSET). The LTC6902 also provides an optional ■ One External Resistor Sets the Frequency spread spectrum frequency modulation (SSFM) capability ■ One External Resistor Sets Percent Frequency that can be activated and controlled by an additional Spreading external resistor (RMOD). ■ 400µA Typical Supply Current, VS = 3V, 1MHz The LTC6902’s master oscillator is controlled by the RSET ■ Frequency Error ≤1.5% Max, 5kHz to 10MHz resistor and has a range of 100kHz and 20MHz. In order (TA = 25°C) to accommodate a wider output frequency range, a pro- ■ Frequency Error ≤ 2% Max, 5kHz to 10MHz grammable divider (divide by 1, 10 or 100) is included. (TA = 0°C to 70°C) The integrated programmable multiphase circuit pro- ■ ±40ppm/°C Temperature Stability vides either 2-, 3- or 4-phase waveforms. ■ Fast Start-Up Time: 50µs to 1.5ms ■ 100Ω CMOS Output Driver The LTC6902’s SSFM capability modulates the oscillator’s ■ Operates from a Single 2.7V to 5.5V Supply frequency by a pseudorandom noise (PRN) signal to ■ Available in 10-Lead MS Package spread the oscillator’s energy over a wide frequency band. This spreading decreases the peak electromagnetic radia-
U APPLICATIO S
tion level and improves electromagnetic compatibility (EMC) performance. The amount of frequency spreading ■ Switching Power Supply Clock Reference is programmable by a single additional external resistor ■ Portable and Battery-Powered Equipment (RMOD) and is disabled by grounding the MOD pin. ■ PDAs , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Cell Phones ■ Clocking Switched Capacitor Filters
U TYPICAL APPLICATIO Output Frequency Spectrum With and Without SSFM 500kHz, 4-Phase Clock with 20% Frequency Spreading
0 OUTPUT SPECTRUM 5V R WITH SSFM MOD 10k –20 0.1µF DISABLED R OUTPUT SET 10k SPECTRUM –40 WITH 20% LTC6902 SPREADING V+ SET –60 OPEN DIV MOD PH GND OUT1 OUT4 OUT4 RELATIVE AMPLITUDE (dBm) –80 OUT2 OUT3 OUT3 OUT2 –100 OUT1 400 450 500 550 600 6902 TA01 FREQUENCY (kHz) 6902 TA02 6902f 1