Analog Input

Converter

–REF

+REF

+IN

–IN

V

BAT1

IN1

Battery

On

IN2

GND

C2-C0

(Shown 101 )

B

2.5-V

Reference

Ref ON/OFF

C3

(Shown HIGH)

X+

X–

+VDD

TEMP1

PENIRQ

Y+

Y–

VREF

TEMP0

7.5kΩ

V

BAT2

7.5kΩ

2.5kΩ

Battery

On

2.5kΩ

TSC2003-Q1

SBAS454 – DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com

See Figure 4 for a block diagram of the input multiplexer on the TSC2003, the differential input of the ADC, and

the converter's differential reference.

When the converter enters the Hold mode, the voltage difference between the +IN and –IN inputs (see Figure 4)

is captured on the internal capacitor array. The input current on the analog inputs depends on the conversion

rate of the device. During the sample period, the source must charge the internal sampling capacitor (typically

25 pF). After the capacitor has been fully charged, there is no further input current. The amount of charge

transfer from the analog source to the converter is a function of conversion rate.

Figure 4. Simplified Diagram of the Analog Input

12

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Product Folder Link(s): TSC2003-Q1