TC7126_13 datasheet(7/28 Pages) MICROCHIP

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 2002-2012 Microchip Technology Inc.

DS21458D-page 7

TC7126/A

2.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 2-1.

TABLE 2-1:

PIN FUNCTION TABLE

Pin Number

(40-Pin PDIP)

Normal

(Reversed)

Symbol

Description

(40)

V+

Positive supply voltage.

(39)

Activates the D section of the units display.

(38)

Activates the C section of the units display.

(37)

Activates the B section of the units display.

(36)

Activates the A section of the units display.

(35)

Activates the F section of the units display.

(34)

Activates the G section of the units display.

(33)

Activates the E section of the units display.

(32)

Activates the D section of the tens display.

(31)

Activates the C section of the tens display.

(30)

Activates the B section of the tens display.

(29)

Activates the A section of the tens display.

(28)

Activates the F section of the tens display.

(27)

Activates the E section of the tens display.

(26)

Activates the D section of the hundreds display.

(25)

Activates the B section of the hundreds display.

(24)

Activates the F section of the hundreds display.

(23)

Activates the E section of the hundreds display.

(22)

AB4

Activates both halves of the 1 in the thousands display.

(21)

POL

Activates the negative polarity display.

(20)

LCD Backplane drive output (TC7106A). Digital Ground (TC7107A).

(19)

Activates the G section of the hundreds display.

(18)

Activates the A section of the hundreds display.

(17)

Activates the C section of the hundreds display.

(16)

Activates the G section of the tens display.

(15)

V-

Negative power supply voltage.

(14)

VINT

The integrating capacitor should be selected to give the maximum voltage swing that

ensures component tolerance buildup will not allow the integrator output to saturate.

When analog common is used as a reference and the conversion rate is 3 readings

per second, a 0.047

F capacitor may be used. The capacitor must have a low

dielectric constant to prevent rollover errors. See Section 6.3 “Integrating Capaci-

tor (CINT)”, Integrating Capacitor for additional details.

(13)

VBUFF

Integration resistor connection. Use a 180k

 resistor for a 200mV full-scale range

and a 1.8M

 resistor for a 2V full scale range.

(12)

CAZ

The size of the auto-zero capacitor influences system noise. Use a 0.33

F capacitor

for 200mV full scale, and a 0.033

F capacitor for 2V full scale. See Section 6.1

“Auto-Zero Capacitor (CAZ)”, Auto-Zero Capacitor for additional details.

(11)

VIN-

The analog LOW input is connected to this pin.

(10)

VIN+

The analog HIGH input signal is connected to this pin.

(9)

ANALOG

COMMON

This pin is primarily used to set the Analog Common mode voltage for battery opera-

tion, or in systems where the input signal is referenced to the power supply. It also

acts as a reference voltage source. See Section 7.3 “Analog Common (Pin 32)”,

Analog Common for additional details.

(8)

CREF-

See Pin 34.

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