PCA8591 PHILIPS [NXP Semiconductors], PCA8591 Datasheet - Page 8

• Manufacturer Part Number: PCA8591
• Description: 8-bit A/D and D/A converter
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
7.3
The third byte sent to a PCF8591 device is stored in the
DAC data register and is converted to the corresponding
analog voltage using the on-chip D/A converter. This D/A
converter consists of a resistor divider chain connected to
the external reference voltage with 256 taps and selection
switches. The tap-decoder switches one of these taps to
the DAC output line (see Fig.5).
The analog output voltage is buffered by an auto-zeroed
unity gain amplifier. This buffer amplifier may be switched
on or off by setting the analog output enable flag of the
control register. In the active state the output voltage is
held until a further data byte is sent.
1998 Jul 02
8-bit A/D and D/A converter
D/A conversion
Fig.5 DAC resistor divider chain.
8
The on-chip D/A converter is also used for successive
approximation A/D conversion. In order to release the
DAC for an A/D conversion cycle the unity gain amplifier is
equipped with a track and hold circuit. This circuit holds the
output voltage while executing the A/D conversion.
The output voltage supplied to the analog output AOUT is
given by the formula shown in Fig.6. The waveforms of a
D/A conversion sequence are shown in Fig.7.
Product specification
PCF8591