L6229

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3.7 NON-DISSIPATIVE OVERCURRENT DETECTION and PROTECTION

The L6229 integrates an Overcurrent Detection Circuit (OCD) for full protection. This circuit provides Output-to-

Output and Output-to-Ground short circuit protection as well. With this internal over current detection, the exter-

nal current sense resistor normally used and its associated power dissipation are eliminated. Figure 20 shows

a simplified schematic for 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-

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

capability of 4mA connected to pin DIAG is turned on.

The pin DIAG can be used to signal the fault condition to a

µC or to shut down the Three-Phase Bridge simply

Figure 20. Overcurrent Protection Simplified Schematic

operation can be easily programmed by means of the accurate thresholds of the logic inputs. It is affected

in Figure 23

be chosen according to the desired Disable Time.

are respectively 100K

Ω and 5.6nF that allow obtaining 200µs Disable Time.

+

OVER TEMPERATURE

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

HIGH SIDE DMOS

HIGH SIDE DMOS

OCD

COMPARATOR

TO GATE

LOGIC

INTERNAL

OPEN-DRAIN

40

Ω TYP.

DIAG

EN

µC or LOGIC

D02IN1381