UM1693 datasheet(95/196 Pages) STMICROELECTRONICS

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UM1693

Load compatibility

195

WOFF ~ 0 mJ (dVOUT/dt)OFF = 0.8*16 V/251 µs = 0.051 V/µs

During the HSD channel activation the xenon module behaves like capacitive load

(waveforms / losses equivalent to ~47 µF capacitor). When the input capacitor is charged

(VOUT = nominal) the input current falls to ~0 until the convertor starts (~1.5 ms delay).

The losses during HSD deactivation are below the measurement resolution (capacitive

character of the load).

6.3

Inductive loads

Switching inductive loads such as relays, solenoids, motors etc. can generate transient

voltages of many times the steady-state value. For example, turning off a 12 volt relay coil

can easily create a negative spike of several hundred volts. The M0-7 high-side drivers are

well designed to drive such kind of loads, in most cases without any external protection.

Nevertheless there are physical limits for each component that have to be respected in

order to decide if an external protection is necessary or not.

As a feature of the M0-7 drivers it can be highlighted that a relatively high output voltage

clamping leads to a fast demagnetization of the inductive load.

The aim of this chapter is to have a simple guide how to check the conditions during

demagnetization, how to select a proper HSD (and the external clamping if necessary)

according to the given load.

6.3.1

Turn-on

When a HSD turns on an inductive load the current is increasing with a time constant given

by L/R values, so the nominal load current is not reached immediately. This fact should be

considered in diagnostics software (i.e. to avoid false open-load detection).

Figure 71. HSD turn-on phase with inductive load

UM1693 Datasheet(PDF) 95 Page - STMicroelectronics