L9907N
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 (V
INC
- V
INF
) lower
than the negative NEUTRAL ZONE threshold, V
N-
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 V
ST-
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 V
N+
, 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
鈥滺IGH鈥?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 I
NC
, I
NF
pins. The error due to voltage
drop over the input signal source resistances
R
INC
, R
INF
is minimized with extremely low input
bias currents I
INC
, I
INF
.
The above mentioned resistors (R
INC
, R
INF
) are
necessary for the input current limitation during
the transients on the V
BAT
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.
Figure 2:
Control to feedbacktransfer characteristic
for tracking regulation (V
F
= V
C
within
the nominal V
INC
operating range):
V
BAT
D95AT183A
V
S
-2V
V
F
1.5V
0
1.5V
V
C
V
S
-2V
V
BAT
Figure 3:
Recommended Application Circuit Diagram with L9907N for tracking regulation
(V
F
= V
C
for 1.5V < V
C
< V
S
-2V):
MODULE
V
BAT
D1
I
Q
C
S
V
S
R
PR
R
INC
I
INC
INC
PR
OUT C
R
F
D2
R
C
V
C
R
CF
V
INC
R
INF
V
INF
I
INF
L9907N
V
M
OUT F
I
M
M
V
F
INF
GND
D95AT184
Note:
Recommended value of R
INC
, R
INF
(equivalent input resistance to I
NC
and I
NF
) is 5K鈩?to 10K鈩? Resistor R
CF
should assure that the differential
input voltage |V
INC
- V
INF
| 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.
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