L6235Q datasheet(19/33 Pages) STMICROELECTRONICS

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L6235Q

Circuit description

Doc ID 018997 Rev 2

19/33

Figure 19.

Overcurrent protection simplified schematic

Figure 20 shows the overcurrent detection operation. The disable time tDISABLE before

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

thresholds of the logic inputs. It is affected by both CEN and REN values and its magnitude is

reported in Figure 21. The delay time tDELAY before turning off the bridge, when an

overcurrent has been detected, depends only on the CEN value. Its magnitude is reported in

Figure 22.

CEN is also used for providing immunity to pin EN against fast transient noises. Therefore

the value of CEN should be chosen as big as possible according to the maximum tolerable

delay time and the REN value should be chosen according to the desired disable time.

The resistor REN should be chosen in the range from 2.2 kΩ to 180 kΩ. Recommended

values for REN and CEN are respectively 100 kΩ and 5.6 nF which allow to obtain 200 µs

disable time.

AM02563v1

OVER TEMPERATURE

IREF

I1+I2 / n

I1 / n

HIGH SIDE DMOS

POWER SENSE

1 cell

POWER SENSE

1 cell

POWER SENSE

1 cell

POWER DMOS

n cells

POWER DMOS

n cells

POWER DMOS

n cells

OUT1

OUT2

VSA

OUT3

VSB

I2/ n

I3/ n

OCD

COMPARATOR

TO GATE

LOGIC

INTERNAL

OPEN-DRAIN

RDS(ON)

Ω TYP.

CEN

REN

DIAG

VDD

μC or LOGIC

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