LTC6908-1/LTC6908-2

1

Rev C

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690812 TA01b

FREQUENCY

(FUNDAMENTAL AND HARMONICS SHOWN)

150kHz

0

–10

–20

–30

–40

0

–10

–20

–30

–40

30MHz

SSFM DISABLED

SSFM ENABLED

Resistor Set SOT-23 Oscillator with

Spread Spectrum Modulation

The LTC®6908 is an easy-to-use precision oscillator that

provides 2-outputs, shifted by either 180° or 90°. The

oscillator frequency is programmed by a single external

resistor (RSET) and spread spectrum frequency modula-

tion (SSFM) can be activated for improved electromag-

netic compatibility (EMC) performance.

The LTC6908 operates with a single 2.7V to 5.5V supply

and provides rail-to-rail, 50% duty cycle square wave out-

puts. A single resistor from 10k to 2M is used to select an

oscillator frequency from 50kHz to 10MHz (5V supply).

The oscillator can be easily programmed using the simple

formula outlined below:

fOUT =10MHz • 10k/RSET

The LTC6908’s SSFM capability modulates the output

frequency by a pseudorandom noise (PRN) signal to

decrease the peak electromagnetic radiation level and

improve EMC performance. The amount of frequency

spreading is fixed at ±10% of the center frequency. When

SSFM is enabled, the rate of modulation is selected by

the user. The three possible modulation rates are fOUT/16,

fOUT/32 and fOUT/64.

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Switching Power Supply Clock Reference

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Portable and Battery-Powered Equipment

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Precision Programmable Oscillator

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Charge Pump Driver

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LTC6908-1: Complementary Outputs (0°/180°)

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LTC6908-2: Quadrature Outputs (0°/90°)

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50kHz to 10MHz Frequency Range

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One External Resistor Sets the Frequency

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Optional Spread Spectrum Frequency Modulation

for Improved EMC Performance

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±10% Frequency Spreading

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400µA Supply Current Typical (V+ = 5V, 50kHz)

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Frequency Error ≤1.5% Max (TA = 25°C, V+ = 3V)

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±40ppm/°C Temperature Stability

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Fast Start-Up Time: 260µs Typical (1MHz)

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Outputs Muted Until Stable

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Operates from a Single 2.7V to 5.5V Supply

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Available in Low Profile (1mm) ThinSOT and DFN

(2mm × 3mm) Packages

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AEC-Q100 Qualified for Automotive Applications

2.25MHz, 2.5V/8A Step-Down Regulator

CBYP

44.2k

OUT1

OUT2

fOUT = 10MHz • 10k/RSET

MOD

V+

GND

SET

690812 TA01a

SVIN TRACK

LTC3418

RT

CIN

100 F

0.2 H

LTC6908-1

RUN/SS

ITH

PGOOD

SW

PGND

SGND

SYNC/MODE VFB

PVIN

820pF

1000pF

0.1 F

COUT

100 F

×2

VOUT

2.5V

8A

4.32k

2k

41.2k

2.2M

VIN

2.8V TO 5.5V

4.99k

150kHz to 30MHz Output

Frequency Spectrum

(9kHz Res BW)

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TYPICAL APPLICATION

FEATURES

DESCRIPTION

APPLICATIONS

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