PIN DESCRIPTION.

Vs ( INPUT SUPPLY VOLTAGE PINS).

These are the two input supply voltage pins. The unregulated

input DC voltage can range from 7V to 52V.

With inductive loads the recommended operating maximum

supply voltage is 42V to prevent overvoltage applied to the

DMosfets. In fact considering a full bridge configuration (see

fig. 2), when the bridge is switched off (ENABLE CHOPPING)

the current recirculation produces a negative voltage to the

source of the lower DMOS switches (point A). In this condi-

ductance and current slope can be some Volts. So the drain-

source voltage of T1 and T4 DMOS switches can reach more

due to current decay and to parasitic inductance. For this reason C2 has to be placed as closed as pos-

The device can sustain a 4A DC input current for each of the two Vs pins, in accordance with the

power dissipation.

OUT1, OUT2, OUT3 (OUTPUTS). These are the output pins

that correspond to the mid point of each half bridge. They are

designed to sustain a DC current of 4A.

SENSE1, SENSE2.

SENSE1 is the common source of the lower DMOS of the half

bridge 1 and 2.

SENSE2 is the source of the lower DMOS of the half bridge

3.

Each of these pins can handle a current of 5A.

A resistance, Rsense, connected to these pins provides feed-

back for motor current control.

Care must be taken with the negative voltage applied to these

pins : negative DC voltage lower than -1V could damage the

device. For duration lower than 300ns the device can sustain

pulsed negative voltage up to -4V.

For example, if enable chopping current control method is

used, negative voltage pulses appear to these pins, due to the

current recirculation through the sensing resistor.

Vref ( Voltage Reference).

This is the internal 10V voltage reference pin to bias the logic

and the low voltage circuitry of the device. A 1

µF electrolytic ca-

pacitor connected from this pin to GND ensures the stability of the

DMOS drive circuit. This pin can be externally loaded up to 5mA .

Figure 3 and 4 show the typical behavior of the Vref pin.

Vcp ( CHARGE PUMP ).

This is the internal oscillator output pin for the charge pump.

The oscillator supplied by the

10V Voltage Reference

switches from GND to 10V

with a typical frequency of

-50

-25

0

25

50

75

100

125

150

0

1

2

3

4

5

6

7

8

9

10

11

Tj [°C]

Vref [V]

Vs = 52V

Vs = 24V

Vs = 7V

Vs = 10V

Figure 3. Reference Voltage vs.

Junction Temperature.

0

1020

3040

50

0

2

4

6

8

10

12

Vs [V]

Vref [V]

Tj = 25°C

Figure 4. Reference Voltage vs.

Supply Voltage.

L

ON/OFF

ON/OFF

T1

C

T3

T2

T4

B

A

ON

OFF

Rsense

D98IN938A

S

Figure 2.

AN1088 APPLICATION NOTE

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