LTC6902

7

6902f

or it should be surrounded by a ground shield to prevent

excessive coupling from other PCB traces.

OUT1, OUT2, OUT3, OUT4 (Pins 4, 5, 6 and 7): Oscillator

Outputs. These pins can drive 5k

Ω and/or 10pF loads.

Larger loads may cause inaccuracies due to supply bounce

at high frequencies.

GND (Pin 8): Ground. Should be tied to a ground plane for

best performance.

SET (Pin 10): Frequency Setting Resistor Input. The value

determines the oscillator frequency. The voltage on this

For best performance, use a precision metal film resistor

with a value between 10k and 2M and limit the capacitance

on this pin to less than 10pF.

PI FU CTIO S

MOD (Pin 9): Spread Spectrum Frequency Modulation

of frequency modulation. The output frequency is always

tor. For best performance, use a precision metal film resis-

tor with a value between 10k and 2M and limit the

capacitance on this pin to less than 10pF. The voltage on

this pin is not static. Limiting the capacitance on this pin

is important for the part to perform properly. To disable

the modulation, connect this pin to GND. Grounding the

MOD pin disables the modulation and shuts down the

modulation circuitry to save power. Leaving the pin open

to disable the modulation is not recommended. While

result of 0% modulation, the open pin is susceptible to

external noise coupling that can effect frequency accuracy.

BLOCK DIAGRA

–

+

1

10

9

MOD

CURRENT MIRROR

G = 1

MASTER OSCILLATOR

PROGRAMMABLE

DIVIDER

÷N

(N = 1, 10 OR 100)

÷3200

6902 BD

9-BIT PRBS

GENERATOR

REF

MULTIPLYING

DAC

7

MULTIPHASE

CIRCUIT

SELECTS BETWEEN

MULTIPHASE

OPTIONS AND

÷M

2-PHASE (M = 1)

3-PHASE (M = 3)

4-PHASE (M = 4)

SET

+

–

2

3

4

DIV

PH

OUT1

5

OUT2

6

OUT3

7

OUT4