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Chapter 23
Analog-to-Digital Converter/
Brownout Detector
The Analog to Digital Converter (ADC) is an AMBA-compliant SoC peripheral that con-
nects as a slave to the APB. The ADC block consists of an 8-channel, 10-bit Analog-to-
Digital Converter with integrated Touch Screen Controller. The complete touch screen
interface is achieved by combining the front-end biasing, control circuitry with analog-to-
digital conversion, reference generation, and digital control.
The ADC has a bias-and-control network that allows correct operation with both 4- and
5-wire touch panels. A 16-entry × 16-bit wide FIFO holds a 10-bit ADC output and a 4-bit
tag number. When the screen is touched, it pushes the conductive coating on the cover-
sheet against the coating on the glass, making electrical contact. The voltages produced
are the analog representation of the position touched. The voltage level of the coversheet
is converted continuously by the ADC and monitored by the system.
Figure 23-1 shows a block diagram of the ADC.
6/25/03
23-1
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