DAC0832 circuit in D/A converter

DAC0832 is a monolithic DC output 8-bit digital/analog converter made using CMOS technology. As shown in Figure 1, it consists of four parts: an inverted T-type R-2R resistor network, an analog switch, an operational amplifier, and a reference voltage VREF. The analog quantity V0 output by the operational amplifier is:

It can be seen from the above formula that the output analog quantity is proportional to the input digital quantity (), which realizes the conversion from digital quantity to analog quantity.

An 8-bit D/A converter has 8 inputs (each of which is one bit of an 8-bit binary number) and one analog output. The input can have 28 = 256 different binary configurations, and the output is one of 256 voltages, that is, the output voltage is not any value within the entire voltage range, but can only be 256 possible values. Figure 2 is the logic block diagram and pin arrangement of DAC0832.

Figure 2

D0~D7: Digital signal input terminal.

ILE: Input register enable, high level is valid.

CS: Chip select signal, low level is valid.

WR1: Write signal 1, low level is valid.

XFER: Transmit control signal, low level is valid.

WR2: Write signal 2, low level is valid.

IOUT1, IOUT2: DAC current output terminals.

Rfb: It is the feedback resistor of the external operational amplifier integrated in the chip.

Vref: reference voltage (-10~10V).

Vcc: is the source voltage (+5~+15V).

AGND: analog ground NGND: digital ground, can be connected together with AGND.

The output of DAC0832 is current, and it is generally required to output voltage, so it must be converted into voltage through an external operational amplifier. The experimental circuit is shown in Figure 3.

Figure 3

IN0~IN7: 8-channel analog signal input terminals.

A1, A2, A0: Address input terminals. ALE address latch allows input signals. A positive pulse is applied to this pin. The rising edge is effective. At this time, the address code is latched, thereby selecting the corresponding analog signal channel for A/D conversion.

START: Start signal input terminal. A positive pulse should be applied to this pin. When the rising edge arrives, the internal successive approximation register is reset. After the falling edge arrives, the A/D conversion process starts.

EOC: Conversion end output signal (conversion acceptance flag), high level is valid.

OE: Input enable signal, high level is valid.

CLOCK (CP): Clock signal input terminal, the external clock frequency is generally 640kHz.

Vcc: +5V single power supply.

Vref(+), Vref(-): The positive and negative poles of the reference voltage. Generally, Vref(+) is connected to the +5V power supply, and Vref(-) is connected to the ground.

D7~D0: Digital signal output terminals. Any of the 8 analog signals can be selected for A/D conversion by the three address input terminals A2, A1, and A0.