ADPA7008AEHZ-R7 datasheet(21/28 Pages) AD

21 / 28 page

Data Sheet

ADPA7008

BIASING THE ADPA7008 WITH THE LOW NOISE LTM8063

analog.com

Rev. 0 | 21 of 28

The LTM8063 is a Silent Switcher voltage regulator that meets the

bias requirement for the positive drain supply of the ADPA7008.

The regulator provides a drain bias voltage that is constant over

load current variations. Figure 70 shows a circuit that derives the

5 V VDD supply voltage from an input rail that can vary from 6.5 V

to 40 V (which is the VIN range of the LTM8063). The LTC8063 is

configured using external components to generate a 5 V VDD supply

capable of up to 2 A. Figure 71 shows a plot of the measured

noise figure vs. frequency of this circuit with a comparison to that

measured with a bench supply, for reference.

Figure 70. Application Circuit Using the LTM8063 for Low Noise Drain

Voltage Generation for the ADPA7008

Figure 71. ADPA7008 Noise Figure vs. Frequency Measured for VDD Using

the LTM8063 vs. a Bench Supply for Reference

A low current (<<1 mA) negative VGG is also required to provide the

constant VGG bias voltage. For this, the ADP5600 is recommended.

As previously noted, the ADPA7008 VDD and VGG voltages must be

correctly sequenced during power-on and power-off.

Figure 72 shows a complete circuit that includes positive drain

voltage generation, negative gate voltage generation, and the pow-

er-on and power-off sequencing. This circuit supports an external

input voltage (VIN) range of 12 V to 16 V.

ADPA7008AEHZ-R7 Datasheet(PDF) 21 Page - Analog Devices