DAC0832 pin diagram, function introduction, principle circuit diagram:
The DAC0832 is a D/A conversion chip with a sampling frequency of eight bits. The integrated circuit has two input registers, which make the DAC0832 chip have three input modes of double buffering, single buffering and straight through, so as to suit the needs of various circuits (such as requirements). Multiple D/A asynchronous input, synchronous conversion, etc.). Therefore, the application of this chip is very extensive. Some important information about the application of DAC0832 is shown in the following figure:
The D/A conversion result is output in the form of current. If a corresponding analog voltage signal is required, it can be implemented with a linear input amplifier with high input impedance. The feedback resistor of the op amp can be referenced to the on-chip inherent resistance through the RFB terminal, or it can be externally connected. The DAC0832 logic input meets TTL levels and can be directly connected to TTL or microcomputer circuits.
DAC0832 pin function description:
DI0~DI7: Data input line, TLL level.
ILE: The data latch allows the control signal input line to be active high.
CS: Chip select signal input line, active low.
WR1: Write strobe signal for the input register.
XFER: Data transmission control signal input line, active low.
WR2: Write the strobe input line for the DAC register.
Iout1: Current output line. When the input is all 1, Iout1 is the largest.
Iout2: Current output line. Its value is a constant with the sum of Iout1.
Rfb: feedback signal input line, there is feedback resistor inside the chip.
Vcc: power input line (+5v~+15v)
Vref: Reference voltage input line (-10v~+10v)
AGND: Analog ground, analog signal and reference ground for the reference power supply.
DGND: Digital ground, the two ground lines are better at the reference power supply.
Internal structure and external structure of DAC0832:
Internal structure of DAC0832
The internal structure of the DAC0832 is shown in Figure 10.9. There are two levels of latches in the DAC0832. The first stage latch is called the input register and its latch signal is ILE. The second stage latch is called the DAC register. Its latch signal is the transmission control signal. . Because of the two-stage latch, the DAC0832 can operate in a double buffer mode, that is, the next digital quantity is acquired while the analog signal is being output, which can effectively improve the conversion speed. In addition, the two-stage latch can also realize the synchronous output of multiple converters by using the second-stage latch signal when multiple D/A converters are working simultaneously.
In Figure 10.9, LE is high, with When it is low, Is high, the output of the input register changes with the input; thereafter, when When going from low to high, To be low, the data is latched into the input register, at which point the output of the input register no longer changes as the input data changes. For the second stage latch, with When it is low at the same time, High, the output of the DAC register changes following its input; thereafter, when When going from low to high, Go low and latch the data in the input register into the DAC register.
DAC0832 external connection
The external connection line of the DAC0832 is shown in Figure 10.10.
How the DAC0832 works
The DAC0832 performs D/A conversion, and the data can be latched in two ways.
The first method is to make the input register operate in the latched state, while the DAC register operates in the pass-through state. Specifically, it is to make with Both are low, the latched strobe of the DAC register is not passed through the active level; in addition, the control signal ILE of the input register is at a high level, At a low level, so when When a negative pulse is received, one conversion can be completed.
The second method is to make the input register operate in the through state, while the DAC register operates in the latched state. Just make with Low level, ILE is high level, so that the latch strobe signal of the input register is in an inactive state and is through; with When a negative pulse is input to the terminal, the DAC register is operated in a latched state, and latched data is supplied for conversion.
According to the above different control methods for the input register and DAC register of DAC0832, DAC0832 has the following three working modes:
(1) Single buffering method. The single buffer mode is to control the input register and the DAC register to receive data at the same time, or to use the input register to connect the DAC register to the through mode. This method is suitable for situations where there is only one analog output or several analog asynchronous outputs.
(2) Double buffering. The double buffering method firstly receives the data from the input register, and then controls the output data of the input register to the DAC register, that is, the input data is latched twice. This method is suitable for the plot of multiple D/A conversion sync outputs.
(3) Direct mode. The pass-through mode is that the data is not latched by the two-stage latch, ie , , , Both are grounded and ILE is connected to a high level. This method is suitable for continuous feedback control lines, but in use, it must be connected to the CPU through an additional I/O interface to match the CPU and D/A conversion.
DAC0832 application circuit program
A/D data conversion with ADC0809
(A) D / A converter DAC0832
The DAC0832 is a monolithic DC output 8-bit digital-to-analog converter fabricated in a CMOS process. As shown in Figure 4-82, it consists of an inverted T-type R-2R resistor network, an analog switch, an operational amplifier, and a reference voltage VREF. The analog quantity V0 of the op amp output is:
As can be seen from the above equation, the analog quantity of the output and the digital quantity of the input ( In direct proportion, this achieves a conversion from digital to analog.
An 8-bit D/A converter has 8 inputs (each of which is a bit of an 8-bit binary number) and has an 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 in the entire voltage range, but only 256 possible values. Figure 4-83 shows the logic block diagram and pinout of the DAC0832.
The DAC0832 outputs current, which is generally required to be voltage, so it must be converted to a voltage by an external op amp. The experimental circuit is shown in Figure 4-84:
IN0~IN7: 8 analog signal inputs.
A1, A2, A0: Address input. The ALE address latch allows the input signal. A positive pulse is applied to this pin, and the rising edge is valid. At this time, the address code is latched, thereby strobing the corresponding analog signal channel for A/D conversion.
START: Start signal input, 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), active high.
OE: Input enable signal, active high.
CLOCK (CP): The clock signal input terminal, the external clock frequency is generally 640kHz.
Vcc: +5V single power supply. ,
Vref(+), Vref(-): positive and negative electrodes of the reference voltage. Generally, Vref(+) is connected to +5V power supply, and Vref(-) is grounded.
D7~D0: Digital signal output. A/D conversion is performed by strobing any one of the eight analog signals by the three address inputs of A2, A1, and A0.
The program implementation of the DAC0832 application circuit D/A conversion is given below:
The DAC0832 implements a D/A conversion, and the following blocks can be used. Set the data to be converted to be placed in the 1000H unit.
MOV BX, 100H
MOV AL, [BX] ; take conversion data
MOV DX, PORTA; PORTA is the D/A converter port address
OUT DX, AL
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