L9924L datasheet(39/84 Pages) STMICROELECTRONICS

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L9924L

Electrical specifications

4.3.15

Pin "LHC"

This pin must be used in place of L pin, to connect the lamp when externals MOS are used

to drive the lamp and the auxiliary load relay. It acts like the L pin, when the switch "Key"

(see Figure 18) is closed (i.e. V(LHC)>VLHCHTh) the device exits stand-by condition. The

presence of the key is detected in alarm condition by regulating the voltage on LHC pin to

VLHCfault=1.26 V (typ.), when suggested external low-side MOS is biased at its typical

current.

The voltage of this pin is monitored respect to GND and A+/B+ in order to protect the

external high side and low side MOS. When the external low side is turned on, if its drain

(i.e. LHC) voltage becomes greater than VLHCLSx respect to GND the external power is

switched off and bit 0 of SPI read register 0x12 is set [12.4.6].

When the external high side is turned on, if its drain (i.e. A+/B+) voltage becomes greater

than VLHCHSx respect to LHC the external power is switched off and bit 1 of SPI read

VLHCLSx and VLHCHSx thresholds can be selected by means of bits 0 and 1 of SPI write

These diagnostic functions take place when GLS voltage with respect to GND is higher than

VGLSTh parameter for low side MOS and when GHS voltage with respect to LHC is higher

than VGHsTh parameter for high side MOS.

Table 24. Electrical characteristics pin "LHC"

Symbol

Parameter

Test Condition

Min.

Typ.

Max. Unit

1ILHCpulldw

Pull down current

Reg(0x09.2) = b0

Reg(0x09.7) = b0

I(LHC) > 0 @ V(LHC) = 0.7 V

ILHCpulldw=ILHCpulldw,weak +

ILHCpulldw,strong=-ILHCpullup + I(LHC)

-1

2ILHCpulldw,weak

Weak pull-down

current

Reg(0x09.2) = b0

Reg(0x09.7) = b1

I(LHC) < 0 @ V(LHC) = 0.7 V

ILHCpulldw,weak=-ILHCpullup + I(LHC)

-50

µA

3ILHCpullup

Pull-up current

Reg(0x09.3) = b0

ILHCpullup=I(LHC)<0 @ V(LHC)=V(GND)

Current from HS driver injected

into LHC pin

-400

µA

4VLHCfault

LHC alarm

voltage

External low-side PowerMOS: VND5N07

I(D)=IDtyp

-1.26

5VLHCHTh

High Voltage

Threshold key-on

detector

-0.8

0.9

1.0

6VLHCLTh

Low Voltage

Threshold key-on

detector

-0.7

0.8

0.9

7TLHCdelay

Turn-on delay

time

100

µs

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