Datasheet

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-
rent I
REF
. When the output current reaches the detection threshold (typically 5.6A) the OCD comparator signals
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
I
OUTA
I
OUTB
CLOCK
35
17
Start Up or Reset
+
OVER TEMPERATURE
I
REF
(I
1A
+I
2A
) / n
I
1A
/ n
POWER SENSE
1 cell
POWER SENSE
1 cell
POWER DMOS
n cells
POWER DMOS
n cells
HIGH SIDE DMOSs OF
THE BRIDGE A
OUT1
A
OUT2
A
VS
A
I
1A
I
2A
I
2A
/ n
FROM THE
BRIDGE B
OCD
COMPARATOR
OCD
COMPARATOR
TO GATE
LOGIC
INTERNAL
OPEN-DRAIN
R
DS(ON)
40Ω TYP.
C
EN
.
R
EN
.EN
V
DD
µC or LOGIC
D01IN1337