LTC6902 Linear Technology, LTC6902 Datasheet - Page 7

• Manufacturer Part Number: LTC6902
• Description: Multiphase Oscillator
• Manufacturer: Linear Technology

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BLOCK DIAGRA
PI FU CTIO S
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
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
of the resistor (R
determines the oscillator frequency. The voltage on this
pin is held at approximately 1.13V below the V
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.
U
R
R
SET
I
MOD
MOD
U
I
SET
10
1
9
8
I
SET
MOD
I
SET
V
SET
MOD
GND
+
U
) connected between Pin 10 and V
W
CURRENT MIRROR
+
–
V
BIAS
+
–
I
V
SET
–
+
+
and/or 10pF loads.
– V
G = 1
SET
= 1.1V 25%
I
MOD
f
I
MASTER
MASTER
+
voltage.
MASTER OSCILLATOR
= 10MHz • 20k •
MULTIPLYING
+
DAC
MOD (Pin 9): Spread Spectrum Frequency Modulation
Setting Resistor Input. The value of the resistor (R
connected between Pin 9 and V
of frequency modulation. The output frequency is always
modulated down from the frequency set by the R
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
leaving the pin open, R
result of 0% modulation, the open pin is susceptible to
external noise coupling that can effect frequency accuracy.
V
REF
SET
(V
I
MASTER
+
– V
SET
7
)
GENERATOR
9-BIT PRBS
(N = 1, 10 OR 100)
PROGRAMMABLE
DIVIDER N
2
DIV
MOD
3200
SELECTS BETWEEN
+
OPTIONS AND M
, gives the mathematical
2-PHASE (M = 1)
3-PHASE (M = 3)
4-PHASE (M = 4)
determines the amount
MULTIPHASE
MULTIPHASE
CIRCUIT
3
PH
LTC6902
OUT1
OUT2
OUT3
OUT4
SET
6902 BD
resis-
4
5
6
7
MOD
7
6902f
)