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Pin Number

Function

Description

Interface Schematic

11

VGATE

Gate Control pin for external amplifier. Connect to the gate

(base) of the external amplifier. In order to guarantee

stability,a 10μF capacitor should be connected between

the gate (base) terminal of the external amplifier and GND

as close to the amplifier as possible.

12

VDRAIN

Drain voltage. Should be connected to the supply

terminal of the external amplifier. A minimum 100 nF

capacitor has to be placed close to the external amplifier to

improve load regulation.

13

TRIGOUT

Trigger out signal. Generates a HIGH (3.5V) signal when

the active bias system stabilizes. This signal can be

used to trigger next device (ENABLE) if more than one

HMC981LP3E is used in a daisy chain.

15

ISENSE

To adjust the bias current of the external amplifier connect

a resistor (Rsense) from ISENSE pin to GND. Use Eqn.2 to

determine the required Rsense value.

16

VREF

1.5V reference voltage. 0.1uF or greater capacitor to GND

is needed for noise filtering.

Pin Descriptions (Continued)

HMC981LP3E

v02.1222

ACTIVE BIAS CONTROLLER