NCV8460A
www.onsemi.com
13
Reverse Battery
Protection
Load
STAT
GND
5 V
Input
V
out
V
D
R
GND
D
GND
+−
Figure 31. Application Diagram
Reverse Battery Protection
An external resistor R
GND
is required to adequately
protect the device from a Reverse Battery event. The resistor
value can be calculated using the following two formulas.
1. R
GND
≤ 600 mV / (I
d
(on) max)
2. R
GND
≥ (-V
D
) / (-I
gnd
)
Maximum (-I
gnd)
current, which is the reverse GND pin
current, can be found in the Maximum Ratings section.
Several High Side Devices can share same the reverse
battery protection resistor. Please note that the sum of (I
d
(on) max) of all devices should be used to calculate R
GND
value. If the microprocessor ground is not common with the
device ground, R
GND
will produce a voltage offset ((I
d
(on)
max) x R
GND
) with respect to the IN and STAT pins.
This offset will be increased when more than one device
shares the resistor.
Power Dissipation during a reverse battery event is equal
to:
P
D
+
ǒ
* V
D
Ǔ
2
ń R
GND
In the case of high power dissipation due to several
devices sharing R
GND
, it is recommended to place a diode
D
GND
in the ground path as an alternate reverse battery
protection method. When driving an inductive load, a 1 kW
resistor should be placed in parallel with the D
GND
diode.
This method will also produce a voltage offset of ~600 mV
with respect to the IN and STAT pins. This diode can also be
shared amongst several High Side Devices. This voltage
offset will vary if D
GND
is shared by multiple devices.
