L6228 STMicroelectronics, L6228 Datasheet - Page 16

• Manufacturer Part Number: L6228
• Description: DMOS DRIVER FOR BIPOLAR STEPPER MOTOR
• Manufacturer: STMicroelectronics

L6228
Figure 18. Wave Drive Mode
NON-DISSIPATIVE OVERCURRENT PROTECTION
The L6228 integrates an Overcurrent Detection Circuit (OCD) for full protection. 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 current sense resistor normally used and its associated power dissipation are eliminated. Figure 19
shows a simplified 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
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
16/26
C or LOGIC
V
DD
REF
. When the output current reaches the detection threshold (typically 2.8A) the OCD comparator signals
R
C
EN
EN
.
.
EN
Start Up or Reset
40 TYP.
R
DS(ON)
3
2
1
TO GATE
LOGIC
4
8
OPEN-DRAIN
INTERNAL
POWER SENSE
COMPARATOR
5
6
7
D01IN1321
COMPARATOR
1 cell
OCD
OCD
CLOCK
I
I
OUTA
OUTB
POWER DMOS
OVER TEMPERATURE
n cells
2
4
6
OUT1
I
1A
FROM THE
BRIDGE B
8
/ n
(I
1A
I
A
REF
I
2
1A
+I
VS
2A
4
+
) / n
A
I
2A
6
OUT2
I
8
2A
POWER DMOS
A
/ n
n cells
HIGH SIDE DMOSs OF
THE BRIDGE A
D01IN1337
POWER SENSE
1 cell