MLX10801 Ver la hoja de datos (PDF) - Melexis Microelectronic Systems

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MLX10801

Power LED driver for automotive applications Power saving low side coil driver Electronic fuse

Melexis Microelectronic Systems  

IC specification MLX10801

Power LED driver for automotive applications

Power saving low side coil driver

Electronic fuse

1.2. Coil driver applications

1.2.1. Coil driver schematic diagram

Cap for EMC directly

on the connector

VBAT

10...100uF

100nF

Calibration point

GND

Calibration

point

VS

GND

TEST

CALIB

47k

optional cap for

EMC reduction

CONTR

DRVOUT

RSENSE

DSENSE

RF

COIL

Calibration points

RSENSE

CF

1.2.2. Coil driver application notes

The purpose of this application is to drive a coil in a power saving efficient way using a switched mode power

supply. Coils of 10mH…5H can be driven. Attention has to be drawn to the maximum allowed current which

must not be exceeded.

In case of high inductive coils and/or longer cables between the IC and the coil, CF and RF might be needed for

reducing electromagnetic emissions.

When the driver switches on, the coil still contains a certain amount of energy, which is connected to a high voltage

on node COIL. Via the RDSon of the driver this voltage together with switching oscillations is then coupled to

RSENSE. If these switching oscillations do not disappear within the debouncing time of the comparator (typically

1µs) the driver is switched off immediately, an effect known as “parasitic switching”. A solution to that could be:

• CF, RDSon+ RF form a filter

• CF only acts in case the driver switches ON (in the OFF state it is quickly discharged by RSENSE)

• RDSon + RF should be larger than RSENSE

• RSENSE and CF must be directly connected to pin RSENSE

• CF and RF must be figured out in the application. However, typical start values are RF=0 (not used)

and CF=1.5uF.

3901010801

Author: TFR revised: RAH/SSZ

Page 8/41

Rev 021 14/July/05

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