19
9120A–AUTO–01/08
ATA6831/ATA6832 Driver ICs
Figure 8-4.
Inductive Pulse at Low-side Output; Channel 1: Gradient of V
out
[10V Offset],
Channel 2: Gradient of I
out
[200 mA/Div.], Pulse Energy: W
L
= 10 mJ.
8.3
Discharger Circuit
Many applications use an inverse-polarity protection diode, such as D1 in
, in the
power supply feed to prevent any damage if V
S
is applied with the wrong polarity. Despite the
popularity of this method, it involves a risk of damage.
During inhibit mode, the IC consumes only an extremely low current IVS, such as 5 µA at maxi-
mum. Any peaks on the supply voltage (V
pk
in
) gradually charge the blocking
capacitor (C9 in
). D1 prevents the capacitor from discharging via the power supply.
Because of the extremely small quiescent current, discharging via the IC can also be neglected.
This means that during long periods in inhibit mode, the IC’s supply voltage could increase con-
tinuously until the maximum supply voltage limit of 40V is exceeded, damaging the IC.
ATA6831, therefore, features a discharger circuit that prevents such unwanted effects. If V
S
exceeds a threshold value of approximately 27V, the blocking capacitor is discharged via an
integrated resistor until V
S
falls again below the threshold.
Figure 8-5.
Functional Principle of the Discharger Circuit
ATA6831
VS
V
pk
V
batt
C9
D1
2 k
Ω
26.8V
