L6208

16/27

Figure 18. Wave Drive Mode

NON-DISSIPATIVE OVERCURRENT PROTECTION

The L6208 integrates an Overcurrent Detection Circuit (OCD). This circuit provides protection against a short

circuit to ground or between two phases of the bridge. With this internal over current detection, the external cur-

rent sense resistor normally used and its associated power dissipation are eliminated. Figure 19 shows a sim-

plified schematic of the overcurrent detection circuit.

To implement the over current detection, a sensing element that delivers a small but precise fraction of the out-

put current is implemented with each high side power MOS. Since this current is a small fraction of the output

current there is very little additional power dissipation. This current is compared with an internal reference cur-

a fault condition. When a fault condition is detected, the EN pin is pulled below the turn off threshold (1.3V typ-

ical) by an internal open drain MOS with a pull down capability of 4mA. By using an external R-C on the EN pin,

the off time before recovering normal operation can be easily programmed by means of the accurate thresholds

of the logic inputs.

Figure 19. Overcurrent Protection Simplified Schematic

2

4

2

D01IN1321

4682468

6

8

CLOCK

35

17

Start Up or Reset

+

OVER TEMPERATURE

POWER SENSE

1 cell

POWER SENSE

1 cell

POWER DMOS

n cells

POWER DMOS

n cells

HIGH SIDE DMOSs OF

THE BRIDGE A

FROM THE

BRIDGE B

OCD

COMPARATOR

OCD

COMPARATOR

TO GATE

LOGIC

INTERNAL

OPEN-DRAIN

40

Ω TYP.

µC or LOGIC

D01IN1337