ADC 0808/0809 Family

ADC 0808/0809 Family

The ADC 0808 and ADC 0809 are monolithic CMOS devices with an 8-channel multiplexer. These devices are also designed to operate from common microprocessor control buses, with tri-state output latches driving the data bus.

The main features of these devices are :

Features

• 8-bit successive approximation ADC.

• 8-channel multiplexer with address logic.

• Conversion time 100 ,us.

• It eliminates the need for external zero and full-scale adjustments.

• Easy to interface to all microprocessors.

• It operates on single 5 V power supply.

• Output meet TTL voltage level specifications.

Fig. 13.5.1 shows pin diagram of 0808/0809 ADC.

ADC 0808/0809 has eight input channels, so to select desired input channel, it is necessary to send 3-bit address on A, B and C inputs. The address of the desired channel is sent to the multiplexer address inputs through port pins. After at least 50 ns, this address must be latched. This can be achieved by sending ALE signal. After another 2.5 ,us, the start of conversion (SOC) signal must be sent high and then low to start the conversion process. To indicate end of conversion ADC 0808/0809 activates EOC signal. The microprocessor system can read converted digital word through data bus by enabling the output enable signal after EOC is activated. This is illustrated in Fig. 13.5.2.