Datasheet

Reverse polarity protection VN808CM-E
12/21 DocID11456 Rev 10
6 Reverse polarity protection
Reverse polarity protection can be implemented on board using two different solutions:
1. Placing a resistor (R
GND
) between IC GND pin and load GND
2. Placing a diode between IC GND pin and load GND
If option 1 is selected, the minimum resistance value has to be selected according to the
following equation:
Equation 1
R
GND
≥ V
CC
/I
GND
where I
GND
is the DC reverse ground pin current and can be found in Section 1: Maximum
ratings of this datasheet.
Power dissipated by R
GND
(when V
CC
< 0: during reverse polarity situations) is:
Equation 2
P
D
= (V
CC
)
2
/R
GND
If option 2 is selected, the diode has to be chosen by taking into account VRRM >|V
cc
| and
its power dissipation capability:
Equation 3
P
D
≥ I
S
*V
f
Note: In normal conditions (no reverse polarity) due to the diode, there is a voltage drop between
GND of the device and GND of the system.
Figure 8. Reverse polarity protection
This schematic can be used with any type of load.
Status
Input
i
GND
Output
i
+ Vcc
R
GND
Load
Diode
Status
Input
i
GND
Output
i
+ Vcc
R
GND
Load
Diode