RF2461PCBA-41X datasheet(4/12 Pages) RFMD

4 / 12 page

8-106

RF2461

Rev B6 060925

Function

Description

Interface Schematic

LNA GAIN

Controls the bypass feature of the LNA. A logic low (<1.0V) selects the

bypass mode. A logic high (>2.0V) turns on the LNA.

MIX GAIN

Controls the bypass feature of the mixer preamp. A logic low (<1.0V)

selects the bypass mode. A logic high (>2.0V) turns on the preamp-

preamp.

3LNA IN

LNA input pin.

4VCC1

VCC pin for all circuits except the LO. Buffer/bias circuitry.

5GND1B

LNA emitter. This pin provides the DC path to ground for the LNA. A

lumped element or a transmission line inductor can be placed between

this pin and ground to degenerate the LNA. This will decrease the gain

and increase the IP3 of the LNA. As the value of inductance is

increased, these effects will become more pronounced.

6LNA OUT

LNA output pin.

See pin 3.

ISET2

An external resistor R2 connected to this pin sets the current of the

preamp and the mixer.

ISET1

An external resistor R3 connected to this pin sets the current of the

LNA when IP SET is high (see pin 19).

9GND3B

Ground pin for preamp circuit. A 3.3nH inductor is used between pin 9

and ground to degenerate the mixer preamp. Degenerating the preamp

will reduce the gain, increase the IP3 and affect the preamp input

impedance.

MIX IN

Mixer preamp input pin.

See pin 9.

IF1-

Second differential output pin for the first mixer.

See pin 12.

IF1+

First differential output pin for the first mixer. Open collector. A current

combiner external network performs a differential to single-ended con-

version and sets the output impedance. A DC blocking cap must be

present if the IF filter input has a DC path to ground. Mixer (IF2+ and

IF-) needs to “see” a differential impedance between 2k

Ω to 4kΩ.

BYPASS

Bypass pin for the LO bias reference.

IF2-

Second differential output pin for the second mixer.

See pin 15.

LNA GAIN

MIX GAIN

LNA IN

LNA OUT

GND1B

MIX IN

GND3B

VCC2

IF1-

IF1+

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