MHW720A1 MHW720A2

2

MOTOROLA RF DEVICE DATA

APPLICATIONS INFORMATION

Nominal Operation

All electrical specifications are based on the nominal

conditions of Vs1 (Pin 5) and Vs2 (Pin 3) equal to 12.5 Vdc

and with output power equaling 20 watts. With these condi-

tions, maximum current density on any device is 1.5 x 105

A/cm2 and maximum die temperature with 100

° base plate

temperature is 165

°. While the modules are designed to

have excess gain margin with ruggedness, operation of

these units outside the limits of published specifications is

not recommended unless prior communications regarding in-

tended use has been made with the factory representative.

Gain Control

This module is designed for wide range Pout level control.

The recommended method of power output control, as

shown in Figure 3, is to fix Vs1 and Vs2 at 12.5 Vdc and vary

the input RF drive level at Pin 7.

In all applications, the module output power should be lim-

ited to 20 watts.

Decoupling

Due to the high gain of the three stages and the module

size limitation, the external decoupling network requires

careful consideration. Both Pins 3 and 5 are internally by-

passed with a 0.018

µF chip capacitor effective for frequen-

cies from 5 through 470 MHz. For bypassing frequencies

below 5 MHz, networks equivalent to that shown in the test

fixture schematic are recommended. Inadequate decoupling

will result in spurious outputs at certain operating frequen-

cies and certain phase angles of input and output VSWR less

than 4:1.

Load Mismatch

During final test, each module is load mismatch tested in a

fixture having the identical decoupling network described in

Figure 1. Electrical conditions are Vs1 and Vs2 equal 15.5 V,

load VSWR infinite, and output power equal to 30 watts.

Mounting Considerations

To insure optimum heat transfer from the flange to heat-

sink, use standard 6–32 mounting screws and an adequate

quantity of silicon thermal compound (e.g., Dow Corning

340). With both mounting screws finger tight, alternately

torque down the screws to 4–6 inch pounds. The heatsink

mounting surface directly beneath the module flange should

be flat to within 0.005 inch to prevent fracturing of ceramic

substrate material. For more information on module mount-

ing, see EB–107.

MHW720A BLOCK DIAGRAM

L2

MHW720A Text Fixture Schematic

Z1, Z2 50

Ω Microstripline

L1, L2 Ferroxcube VK200–20/4B

Pin 2

C1, C4, C5, C6 1.0

µF Tantalum 25 V

Pin 4

L1

C1

C2

Pin 7

50

Ohm

Load

Z2

Pin 1

C7 47

µF Tantalum, 25 V

C2, C3 0.1

µF Ceramic

C4

C7

C6

C3

Pin 3

Vs1

Vs2

Pin 5

C5

Pin 6

MICROLAB/ FXR AD 10N

Generator

Signal

10 dB

Z1

NOTE: No Internal D.C. blocking on input pin.

Figure 1. UHF Power Amplifier Test Setup