L6226

Circuit description

Doc ID 9452 Rev 4

13/31

4.3

Non-dissipative overcurrent detection and protection

An overcurrent detection circuit (OCD) is integrated. This circuit can be used to provides

protection against a short circuit to ground or between two phases of the bridge as well as a

roughly regulation of the load current. With this internal over current detection, the external

current sense resistor normally used and its associated power dissipation are eliminated.

Figure 9 shows a simplified schematic of the overcurrent detection circuit for the Bridge A.

Bridge B is provided of an analogous 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-rent IREF. When the

output current reaches the detection threshold Isover the OCD comparator signals a fault

condition. When a fault condition is detected, an internal open drain MOS with a pull down

capability of 4 mA connected to OCD pin is turned on. Figure 10 shows the OCD operation.

This signal can be used to regulate the output current simply by connecting the OCD pin to

EN pin and adding an external R-C as shown in Figure 9. The off time before recovering

normal operation can be easily programmed by means of the accurate thresholds of the

logic inputs.

following the equations:

●

●

to 40 k

Ω.

means of the accurate

Figure 13.

disable time.