VN808CM-32-E Datasheet, PDF (13/18 Pages) STMicroelectronics – Octal channel high side driver

VN808CM-32-E
7
Reverse polarity protection
Reverse polarity protection
A schematic solution to protect the IC against a reverse polarity condition is proposed.
This schematic is effective with any type of load connected to the outputs of the IC.
The R_GND resistor value can be selected according to the following conditions to be met:
1. R_GND ≤ 600 mV / (I_S in ON state max).
2. R_GND ≥ (-V_CC) / (-I_GND)
where -I_GND is the DC reverse ground pin current and can be found in the absolute
maximum rating section of the device datasheet.
The power dissipation associated to R_GNG during reverse polarity condition is:
PD = (-V_CC)²/R_GND
This resistor can be shared by several different ICs. In such case I_S value on formula (1) is
the sum of the maximum ON-state currents of the different devices.
Please note that if the microprocessor ground and the device ground are separated then the
voltage drop across the R_GND (given by I_S in ON state max * R_GND) produce a difference
between the generated input level and the IC input signal level. This voltage drop will vary
depending on how many devices are ON in the case of several high side switches sharing
the same R_GND.
Figure 8. Reverse polarity protection
+ Vcc
Status_i
Input_i
Output_i
R_GND
GND
(Optional)
Load
13/18