VB525SP datasheet(13/19 Pages) STMICROELECTRONICS

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VB525SP-E

Application schematic

Doc ID 18022 Rev 2

13/19

Application schematic

Figure 8.

Application diagram

4.1

Principle of operation

The VB525SP-E is mainly intended as a high voltage power switch device driven by a logic

level input and interfaces directly to a high energy electronic ignition coil.

The input VIN of the VB525SP-E is fed from a low power signal generated by an external

controller that determines both dwell time and ignition point. During VIN high (≥ 4V) the

VB525SP-E increases current in the coil to the desired, internally set current level.

After reaching this level, the coil current remains constant until the ignition point, that

corresponds to the transition of VIN from high to low (typ. 1.9 V threshold).

During the coil current switch-off, the primary voltage HVC is clamped at an internally set

value Vcl, typically 380 V. The transition from saturation to desaturation, coil current limiting

phase, must have the ability to accommodate an overvoltage.

A maximum overshoot of 20 V is allowed.

4.2

Feedback

When the collector current exceeds 4.5 A, the feedback signal is turned high and it remains

so, until the input voltage is turned-off.

μP

1nF

18K

VCC

HVC

GND

FLAG

Vbat

μF

100nF

LGND

VIN

+5V

Note:

ENABLE pin can be alternatively connected to LGND.

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