LTC6948 datasheet(12/38 Pages) AD

12 / 38 page

LTC6948

6948fa

For more information www.linear.com/LTC6948

TB (Pin 16): VCO Bypass. This output has a 2k resistance

and must be bypassed with a 2.2µF ceramic capacitor to

GND. It is normally connected to CMA, CMB, and CMC with

a short trace. Do not couple this pin to any other signal.

CMA,CMB,CMC(Pins18,19,20):VCOBiasInputs.These

inputs are normally connected to TB with a short trace

and bypassed with a 2.2µF ceramic capacitor to GND. Do

not couple these pins to any other signal. For best phase

noise performance, DO NOT place a trace between these

pads underneath the package.

BVCO (Pin 22): VCO Bypass Pin. This output must be

bypassed with a 1µF ceramic capacitor to GND. Do not

couple this pin to any other signal.

VVCO+ (Pin 23): 4.75V to 5.25V Positive Supply Pin for

VCO Circuitry. This pin should be bypassed directly to the

ground plane using a 0.01µF ceramic capacitor as close

to the pin as possible.

GND (24): Negative Power Supply (Ground). This pin is

attached directly to the die attach paddle (DAP) and should

be tied directly to the ground plane.

VCP+ (Pin 25): 4V to 5.25V Positive Supply Pin for Charge

Pump Circuitry. This pin should be bypassed directly to

the ground plane using a 0.1µF ceramic capacitor as close

to the pin as possible.

CP (Pin 26): Charge Pump Output. This bidirectional cur-

rentoutputisnormallyconnectedtotheexternalloopfilter.

See the Applications Information section for more details.

VREF+ (Pin 27): 3.15V to 3.45V Positive Supply Pin for

Reference Input Circuitry. This pin should be bypassed

directly to the ground plane using a 0.1µF ceramic capaci-

tor as close to the pin as possible.

pin FuncTions

LTC6948 Datasheet(PDF) 12 Page - Analog Devices