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L9904

MOTOR BRIDGE CONTROLLER

STMicroelectronics 

L9904

3 FUNCTIONAL DESCRIPTION

3.1 General

The L9904 integrated circuit (IC) is designed to control four external N-channel MOS transistors in H-Bridge con-

figuration for DC-motor driving in automotive applications. It includes an ISO9141 compatible interface. A typical

application is shown in fig.9.

3.2 Voltage supply

The IC is supplied via an external reverse battery protection diode to the VVS pin. The typical operating voltage

range is down to 8V.

The supply current consumption of the IC composes of static and a dynamic part. The static current is typically

5.8mA. The dynamical current Idyn is depending of the PWM frequency fPWM and the required gate charge QGate

of the external power mos transistor. The current can be estimated by the expression:

Idyn = 2 · fPWM · QGate

An external power transistor with a gate charge of QGate = 160nC and a PWM frequency of fPWM = 20kHz re-

quires a dynamical supply current of Idyn = 6.4mA.

The total supply current consumption is IVS = 5.8mA + 6.4mA = 12.2mA.

3.3 Extended supply voltage range (ST)

The operating battery voltage range can be extended down to 6V using the additional components shown in

fig.7. A small inductor of L~150H (Ipeak~500mA) in series to the battery supply builts up a step up converter

with the switching open drain output ST. The switching frequency is typical 100kHz with a fixed duty cycle of

50%. The step up converter starts below VVS < 8V, increases the supply voltage at the VS pin and switches off

at VVS > 10V to avoid EME at nominal battery voltage. The diode D2 in series with the ST pin is necessary only

for systems with negative battery voltage. No additional load can be driven by the step up converter.

Figure 10.

VBAT

L1

D1

L9904

VS

C1

C2

D2

ST

-

+

= VSTH

fST

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