Datasheet

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OPERATION - D/A CONVERTER

RRNG

VBIAS

DAC

8-Bits

V+

ARNG

AOUT

TSC2301

SLAS371D – SEPTEMBER 2002 – REVISED AUGUST 2004

The TSC2301 has an onboard 8-bit DAC, configured as shown in Figure 70 . This configuration yields a current

sink (AOUT) controlled by the value of a resistor connected between the ARNG pin and ground. The D/A

converter has a control register, which controls whether or not the converter is powered up. The eight-bit data is

written to the DAC through the DAC data register.

Figure 70. D/A Converter Configuration

This circuit is designed for flexibility in the output voltage at the VBIAS point shown in Figure 70 to accommodate

the widely varying requirements for LCD contrast control bias. V+ can be a higher voltage than the supply

voltage for the TSC2301. The only restriction is that the voltage on the AOUT pin can never go above the

absolute maximum ratings for the device, and should stay above 1.5 V for linear operation.

The DAC has an output sink range which is limited to approximately 1 mA. This range can be adjusted by

changing the value of RRNG shown in Figure 70 . As this DAC is not designed to be a precision device, the

actual value of the output current range can vary as much as ±20%. Furthermore, the current output changes

due to variations in temperature; the DAC has a temperature coefficient of approximately 0.9 uA/ °C.

To set the full-scale current, RRNG can be determined from the graph shown in Figure 71 .