L6226Q

Circuit description

11/28

4.3

Truth table

4.4

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 7 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 output 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

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 8 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 7. The off time before recovering

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

logic inputs.

following the equations:

●

(PROGCL connected to GND)

●

Isover =

to 40 k

Ω.

Table 7.

Truth table

Inputs

Outputs

EN

IN1

IN2

OUT1

OUT2

1.

X = Don't care

X

2.

High Z = High impedance output

High Z

HL

L

GND

GND

HH

L

Vs

GND

HLH

GND

Vs

HH

H

Vs

Vs

11050

R

CL

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