L9907N datasheet(4/8 Pages) STMICROELECTRONICS

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FUNCTIONAL DESCRIPTION

The L9907N is a power comparator with full-

bridge push-pull outputs, intended for driving a

DC motor in the headling adjustment system.

The basic function of the device is shown in the

input-output tranfer characteristic, Fig. 1.

For differential input voltage (VINC -VINF) lower

than the negative NEUTRAL ZONE threshold, VN-

the output voltage is negative (corresponds to

motor direction right), for increasing differential in-

put voltage, this status changes to the zero output

voltage (motor is actively braked), when the differ-

ential input voltage exceeds the VST- stop range

threshold. The output status remains in this condi-

tion as long as the differential input voltage re-

mains within the NEUTRAL ZONE. If the input

voltage increases above the positive NEUTRAL

ZONE threshold VN+, the output voltage become

positive (motor direction left).

Similar behaviour is obtained for decreasing the

input voltage. The output status transitions are

marked with the arrows showing the correspond-

ing direction of the output status variation. The

active braking mode is got with both outputs in

”HIGH” status

The above described behaviour assures high po-

sitioning precision, corresponding to the STOP

RANGE and high noise immunity in the adjusted

condition due to the NEUTRAL ZONE hysteresis

thresholds .

Both the above described thresholds are defined

referring to INC,INF pins. The error due to voltage

drop over the input signal source resistances

RINC,RINF is minimized with extremely low input

bias currents IINC,IINF.

The above mentioned resistors (RINC,RINF) are

necessary for the input current limitation during

the transients on the VBAT line. The input source

resistors must be dimensioned so that in case of

a line transient the input current in the input pin,

clamped with the internal input protection diodes

do not increase over the specified absolute maxi-

mum value.

VBAT

VS -2V

1.5V

VS -2V

VBAT

D95AT183A

Figure 2: Control to feedbacktransfer characteristic

for tracking regulation (VF =VC within

the nominal VINC operating range):

VINC

RINF

RINC

RPR

RCF

L9907N

IINC

INC

VINF

IINF

INF

GND

OUT C

OUT F

VBAT

D95AT184

MODULE

Figure 3: Recommended Application Circuit Diagram with L9907N for tracking regulation

(VF =VC for 1.5V < VC <VS -2V):

Note:

Recommended value of RINC,RINF (equivalent input resistance to INC and INF)is 5K

Ω to 10KΩ. Resistor RCF should assure that the differential

input voltage |VINC -VINF| remains within the NEUTRAL ZONE, when the control signal wire become broken. When this condition is fulfiled the

motor will not change its previous position.

L9907N

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