UM1693 Datasheet, PDF (95/196 Pages) STMicroelectronics – M0-7 standard high-side drivers hardware design guide

UM1693
Load compatibility
W_OFF ~ 0 mJ (dV_OUT/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
(V_OUT = 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
6.3.1
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.
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
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