MC33187 データシートの表示（PDF） - Motorola => Freescale

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MC33187

Long Duration Automotive Timer

Motorola => Freescale 

Freescale SeMmC3i3c18o7nductor, Inc.

DEVICE DESCRIPTION

Pin 1 : RC

Oscillator frequency control. Rt and Ct control the

frequency of the clock oscillator. The period of oscillation is

nominally given by t = RtCt with the overall time period given

by T = 4096 RtCt. However, the following formula is believed

to give a more accurate forecast of the overall time interval

provided by the circuit for values of Rt between 200K and 2M

and values of Ct between 1nF and 1uF.

Formula : T = 4.1 10e-3 (RT * (RT/150)*2.7) *CT.

Pin 2 : GND

Ground : Most negative supply terminal.

Pin 3 : RELAY

Relay output driver. Open collector drive from a Darlington

transistor rated. Icmax = 400mA and Vmax = 18V. The relay

driver output is on (low) during the time period.

Pin 4 : TOGGLE

On/Off Control. A positive going voltage transition on this

input toggles the timer between the On and Off state. If the

timer is On and timing, it may be turned off by a positive going

signal on the toggle pin before the time delay has elapsed.

Pin 5 : VCC

Positive supply terminal. The timer requires a supply

voltage of 5 to 18V applied to Vcc through Rs. An internal 7V

zener limits the Vcc terminal voltage. Cs is included to provide

supply rail decoupling.

Recommended values of Rs and Cs on a standard 12V

vehicle system are Rs = 1KOhm and Cs = 100nF.

APPLICATION

This is the standard operation of this circuit requiring the

minimum of extra components.

The ON/OFF switch is a non-latching push button (or

similar), illuminated by a lamp in parallel with the rear window

defogger. Rin protects the toggle input from supply line

transients with a nominal of Rin = 10KΩ. The relay is intended

to be a standard automotive relay (Rnom = 60Ω) with contacts

rated appropriately for the defogger controlled. Dz with a

nominal value of 16V +-5% is included to provide protection of

the relay drive output transistor against relay turn-off and

supply lines transients.

The type of zener used is dependent of the level of

protection required. An MZD16 will provide adequate

protection for all relay turn-off and low energy supply

transients, while a P6KE16A will provide full protection against

all known transients. If the relay output is to be connected in

any other way or to a non-standard relay, the maximum ratings

quoted under the General Description above should be noted.

Figure 1. .Defogger Timer Operation

Ct

Rt

Cs

Rear

Defogger

Resistor

Batt

Dz

RC

GND

Relay

TS

N/C

N/C

Toggle

Rin

S1

Vcc

Batt

Batt

Rs

MC33187

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