UM1693 datasheet(46/196 Pages) STMICROELECTRONICS

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Protection against battery transients

UM1693

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device level are minimum VIH and maximum IGND(ON), values are both available in

datasheets). Experimental trials have led to fix the below range:

— 47

Ω < R1 < 300 Ω in case of 5 V Input logic level and single or double channel

Hybrid HSD.

— 18

Ω < R1 < 300 Ω in case of 3.3 V Input logic level and quad channel Hybrid

HSD

•

The simple reverse battery network (R1) is not always enough. In case of four channels

Hybrid HSD, a further D+R2 network is required in order to keep the GND pin voltage

drop as little as possible and avoid usage of big space demanding, low ohmic R1

component. R2 must be chosen according to the following limits:

–

Minimum value must limit the current flowing from VCC to GND through the

internal signal clamp structure during the ISO 2a pulse;

–

Maximum value according to maximum GND shift that guarantees device properly

driven ON even in the worst case device limits (relevant parameter to be taken into

account at device level are minimum VIH and maximum IGND(ON), both values are

available in datasheets). Experimental trials have led to suggest below range

(assuming R1 = 270

Ω and drop Voltage on diode of 0.4 V):

— 18

Ω < R2 < 91 Ω

In Figure 25 a test setup is used in order to measure capability of M0-7 Hybrid device, in this

case the VN7004AH-E, to sustain ISO7637-2: (2011) pulses.

Figure 25. Basic Test setup for ISO 7637-2 (2011) pulses applied to VN7004AH-E

UM1693 Datasheet(PDF) 46 Page - STMicroelectronics