mc33187d Freescale Semiconductor, Inc, mc33187d Datasheet - Page 4

• Manufacturer Part Number: mc33187d
• Description: Long Duration Automotive Timer
• Manufacturer: Freescale Semiconductor, Inc

provide a delay in turning the courtesy light off after the
vehicle doors are closed. The components are the same as
the defogger timer and Rt, Ct, Rs and Cs are as described in
the general description above, while Dz and Rin are
described in the description of the defogger timer. S1 to Sn
represent the doors switches which can be basically the
same as for a conventional system, except that only the relay
coil current and not the full lamp current passes through
them.
light is on with the relay current flowing through the switch.
MC33187
The circuit shown demonstrates the use of the timer to
The operation of the circuit is as follows :
While one of the door switches is closed, the courtesy
S1
Sn
Batt
Ct
Freescale Semiconductor, Inc.
Rin
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Dz
Figure 2.
Rt
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Courtesy Light Timer Operation
RC
GND
Relay
Toggle
MOTOROLA
MC33187
the relay coil causes the common connection of the switches
to rise to the voltage permitted by the clamp consisting of Dz
(approximately 16V).
output of the integrated circuit to go low, thus keeping the
relay energised for the period preset, with the direct
connection to Rin ensuring that any switch bounce or noise
during this period cannot cause toggle input to be detected.
Retriggering at the end of the timing period is prevented by
the built in the debounce timer.
As soon as the last switch is opened, the energy stored in
This provides a toggle input via Rin, causing the relay
N / C
N / C
Vcc
TS
Cs
Rs
Batt
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