DRV595

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SLOS808 – DECEMBER 2012

INPUT IMPEDANCE

The DRV595 input stage is a fully differential input stage and the input impedance changes with the gain setting

from 9 k

Ω at 36 dB gain to 60 kΩ at 20 dB gain. Table 1 lists the values from min to max gain. The tolerance of

the input resistor value is ±20% so the minimum value will be higher than 7.2 k

Ω.

Table 2. Recommended Input AC-Coupling Capacitors

GAIN

INPUT IMPEDANCE

20 dB

60 k

Ω

26 dB

30 k

Ω

32 dB

15 k

Ω

36 dB

9 k

Ω

START-UP/SHUTDOWN OPERATION

The DRV595 employs a shutdown mode of operation designed to reduce supply current (Icc) to the absolute

minimum level during periods of non use for power conservation. The SDZ input terminal should be held high

(see specification table for trip point) during normal operation when the amplifier is in use. Pulling SDZ low will

put the outputs to Hi-Z and the amplifier to enter a low-current state. It is not recommended to leave SDZ

unconnected, because amplifier operation would be unpredictable.

GVDD SUPPLY

The GVDD Supply is used to power the gates of the output full bridge transistors. It can also be used to supply

the GAIN/SLV voltage divider. Decouple GVDD with a X5R ceramic 1 µF capacitor to GND. The GVDD supply is

not intended to be used as an external supply. It is recommended to limit the current consumption by using

resistor voltage dividers for GAIN/SLV of 100 k

Ω or more.

BSP AND BSN CAPACITORS

The full H-bridge output stages use only NMOS transistors. Therefore, they require bootstrap capacitors for the

high side of each output to turn on correctly. A 220 nF ceramic capacitor of quality X5R or better, rated for at

least 16 V, must be connected from each output to its corresponding bootstrap input. (See the application circuit

diagram in Figure 13.) The bootstrap capacitors connected between the BSx pins and corresponding output pins

function as a floating power supply for the high-side N-channel power MOSFET gate drive circuitry. During each

high-side switching cycle, the bootstrap capacitors hold the gate-to-source voltage high enough to keep the high-

side MOSFETs turned on.

DIFFERENTIAL OR SINGLE-ENDED INPUTS

The differential input stage of the amplifier cancels any noise that appears on both input lines of the channel. To

use the DRV595 with a differential source, connect the positive lead of the signal source to the IN+ input and the

negative lead of the signal source to the IN– input. To use the DRV595 with a single-ended source, use a

voltage divider to bias IN- to 3.0V, and apply the single-ended signal to IN+.

Copyright © 2012, Texas Instruments Incorporated

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