MPXM2102AS datasheet(633/670 Pages) MOTOROLA

633 / 670 page

MC145011

4–41

Motorola Sensor Device Data

www.motorola.com/semiconductors

TEST

LOW–SUPPLY

TRIP

VSS

OSC

LED

FEEDBACK

SILVER

VDD

IRED

I/O

BRASS

STROBE

DETECT

HORN

TO OTHER

MC145011(s),

ESCAPE LIGHT(S),

AUXILIARY ALARM(S),

REMOTE ALARM(S),

AND/OR AUTO–DIALER

CURRENT

R13*

4.7 TO 22

2.2 M

R55

VISIBLE

LED

47 k

100 k

SW1

MC145011

PUSHBUTTON

TEST

10 M

0.01

µF

C65

1500 pF

100 k

470

R45

100 k

1 TO 22

µF

C4**

0.047

µF

C2*

4700 pF

R14

560

Ω

R11 250 k

IR DETECTOR

8.2 k

R9†

5 k

R10

4.7 k

IR EMITTER

R12

1 k

100

µF

Values for R4, R5, and C6 may differ depending on type of piezoelectric horn used.

* C2 and R13 are used for coarse sensitivity adjustment. Typical values are shown.

† R9 is for fine sensitivity adjustment (optional). If fixed resistors are used, R8 = 12 k, R10 is 5.6 k to 10 k, and R9 is eliminated. When R9

is used, noise pickup is increased due to antenna effects. Shielding may be required.

** C4 should be 22

µF if supply line resistance is high (up to 50 Ω). C4 could be reduced to 1 µF when supply line resistance is < 30 Ω.

V+

Figure 5. Typical Application

PIN DESCRIPTIONS

C1 (Pin 1)

A capacitor connected to this pin as shown in Figure 5

determines the gain of the on–chip photo amplifier during

pushbutton test and chamber sensitivity test (high gain). The

capacitor value is chosen such that the alarm is tripped from

background reflections in the chamber during pushbutton

test.

Av ≈ 1 + (C1/10) where C1 is in pF. CAUTION: The value

of the closed–loop gain should not exceed 10,000.

C2 (Pin 2)

A capacitor connected to this pin as shown in Figure 5

determines the gain of the on–chip photo amplifier except

during pushbutton or chamber sensitivity tests.

Av ≈ 1 + (C2/10) where C2 is in pF. This gain increases

about 10% during the IRED pulse, after two consecutive

local smoke detections.

Resistor R14 must be installed in series with C2. R14

≈

[1/(12

√C2)] – 680 where R14 is in ohms and C2 is in farads.

DETECT (Pin 3)

This input to the high–gain pulse amplifier is tied to the

cathode of an external photodiode. The photodiode should

have low capacitance and low dark leakage current. The

diode must be shunted by a load resistor and is operated at

zero bias.

The Detect input must be ac/dc decoupled from all other

signals, VDD, and VSS. Lead length and/or foil traces to this

pin must be minimized, also. See Figure 6.

STROBE (Pin 4)

This output provides a strobed, regulated voltage refer-

enced to VDD. The temperature coefficient of this voltage is

± 0.2%/°C maximum from – 10° to 60°C. The supply–voltage

coefficient (line regulation) is

± 0.2%/V maximum from 6 to

12 V. Strobe is tied to external resistor string R8, R9, and

R10.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS Datasheet(PDF) 633 Page - Motorola, Inc

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