UM1693 datasheet(23/196 Pages) STMICROELECTRONICS

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UM1693

Reverse battery protection

195

Figure 7. Measurement example (tDEMAG > tD_STBY) with 4.7 kΩ GND resistor

The experimental trials have shown:

•

The operation with high inductivity load (TDEMAG > tD_STBY) is correct even without the

GND resistor (only the diode), knowing that the device GND pin oscillation with period

of tD_STBY may be present (see Figure 6)

•

In all cases, the 10 k

Ω resistor was enough to reduce the GND shift below the logic

input activation level (so eliminate the oscillations)

•

The 4.7 k

Ω appears to be the best compromise between the GND shift safety and

power dissipation during static reverse battery condition (~50 mW)

The value of the resistor should be low enough to be sure that the negative voltage at the

GND pin is suppressed as much as necessary to keep the device off. This means the VGND

should be kept above -1.3 V.

The minimum resistor value is determined by the maximum DC reverse ground pin current

of the HSD in reverse battery condition:

In order to keep the power dissipation on the resistor during reverse battery condition as low

as possible, it is recommended to select the resistor value close to the maximum value

(4.7 k).

GND

BAT reverse

()

GN D reverse

()max

------------------------------------------------

≥

16V

200mA

-------------------

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