PC87591L datasheet(190/437 Pages) NSC

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4.12 DIGITAL TO ANALOG CONVERTER (DAC)

The DAC converts digital input values to analog signals. The DAC support four channels for handling up to four independent

conversions in parallel.

4.12.1 Features

●

8-bit resolution

●

Independent 4-channel D/A converter

●

Fast settling time, 1

µs typical, on 50 pF capacitive load

●

Output range from AGND to AVCC

●

Independent enable/disable for each channel

●

All converters can be automatically disabled in Idle mode

●

Low power consumption when enabled; zero power consumption when disabled

●

Outputs drive 0V when disabled

4.12.2 Functional Description

The DAC has four independent digital-to-analog converters. Each converter generates an output in the range of 0V to AVCC,

with 8-bit resolution. The converters drive the four output pins DA0-3, as shown in Figure 67. An output impedance of 3 K

Ω

allows a settling time of about 1

µs on a 50 pF load.

When a DAC channel is enabled, its output is defined by the value written to its DACDATn register. DACDAT0-3 control

DA0-3, respectively. The maximum output voltage is (255

÷ 256)

* AVCC and is obtained for a value of FF16. The minimum

output, 0V, is obtained for a value of 0016.

The reference voltage of the converters is the AVCC analog power supply voltage. This allows full swing of the outputs from

0V to nearly AVCC.

After reset, all four channels are disabled and the voltage on the DA0-3 outputs is 0V.

In Idle mode, the DAC channels may be enabled or disabled (to reduce power consumption). Two control modes are pro-

vided:

●

Automatic disable of all channels on entering Idle mode

●

Selective disable of channels by software, before entering Idle mode

4.12.3 D/A Conversion

Output Signal

The DAC performs a linear conversion of the input digital value DACDATA7-0 registers to a unipolar analog output signal,

relative to the analog ground pin (AGND).

PC87591L 데이터시트(PDF) 190 Page - National Semiconductor (TI)

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