UM1693 datasheet(39/196 Pages) STMICROELECTRONICS

Part #	UM1693

Description	M0-7 standard high-side drivers hardware design guide

PDF	196 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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39 / 196 page

DocID025505 Rev 1

39/196

UM1693

Protection against battery transients

195

Figure 19. Internal structures involved during application of ISO 7637-2 pulse 1 in a monolithic

HSD and indication of pin voltages

Besides, since the device input may be driven independent from the microcontroller by a

separate HW, which is supplied directly from battery, it’s mandatory to decouple the signal

coming from the microcontroller to the one coming from the limp home circuitry, in order to

avoid any backward supply of one circuit versus the other one. The decoupling is ensured

by a signal diode, placed in series to the Limp Home path connected to the device input.

Dimensioning of the series resistors on I/O line

The resistor value should be calculated according to the maximum injected current to I/O pin

of the used microcontroller. That value can be assumed about 10 mA. So that, the resistors

value should be at least 15 k

Ω (150 V/10 mA):

Ri ≥ 15 kΩ

UM1693 Datasheet(PDF) 39 Page - STMicroelectronics