DRV593

DRV594

SLOS401A - SEPTEMBER 2002 REVISED - OCTOBER 2002

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APPLICATION INFORMATION

PULSE-WIDTH MODULATION SCHEME FOR DRV593 AND DRV594

The pulse-width modulation scheme implemented in the DRV593 and DRV594 eliminates one-half of the full output

filter previously required for PWM drivers. The DRV593 and DRV594 require only one inductor and capacitor for the

output filter. The H/C outputs determine the direction of the current and do not switch back and forth. The PWM outputs

switch to produce a voltage across the load that is proportional to the input control voltage.

COOLING MODE

Figure 18 shows the DRV593 and DRV594 in cooling mode. The H/C outputs (pins 14 - 17) are at ground and the

PWM outputs (pins 24 - 27) create a voltage across the load that is proportional to the input voltage.

The differential voltage across the load is determined using equation (1) and the duty cycle using equation (2). The

differential voltage is defined as the voltage measured after the filter on the PWM output relative to the H/C output.

V

D

V

DD

D

+

V

DD

where

D

duty cycle of the PWM signal

Gain of DRV593/594 (DRV593: 2.3 V/V, DRV594: 14.5 V/V)

Positive input terminal of the DRV593/594

Negative input terminal of the DRV593/594

Power supply voltage

H/C

PWM

Load

Voltage

VDD

VDD

VDD

VDD/2

0

0

0

Figure 18. Cooling Mode

(1)

(2)