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This paper primarily explains the working principle of the serial D/AMAX521, detailing its operational sequence, connection method with a microcontroller, and some related programs. It provides a comprehensive overview of the MAX521, a 2-wire, 8-channel, 8-bit voltage output digital-to-analog converter (DAC). The device features five reference voltage inputs: the first four DACs (DAC0 to DAC3) each have an independent reference input (REF0 to REF3), while the remaining four DACs (DAC4 to DAC7) share a single reference input (REF4). The MAX521 supports a maximum conversion frequency of 400 kbps through its serial interface and built-in software protocol.
The device has a double-buffered input structure, allowing individual or simultaneous updates of the DAC registers, and includes a low-power mode that reduces current consumption to 4 μA. It operates on a single +5V power supply and is available in various package types, including 20-pin DIP, 24-pin SO, and 24-pin SSOP. The pin configuration for the 20-pin DIP version is illustrated in Figure 1.
Applications of the MAX521 include minimal analog systems, data offset/sampling adjustment, industrial process control, and automatic testing equipment. The device’s I2C communication protocol involves two lines: SCL (serial clock) and SDA (serial data). The SCL line is controlled by the master device, while the SDA line transmits data bidirectionally.
The I2C protocol specifies that data changes occur when SCL is low, except during start and stop signals. Each byte transferred follows a high-bit-first format. The communication process begins with a start signal, which occurs when SCL is high and SDA transitions from high to low. A stop signal is generated when SCL is high and SDA transitions from low to high.
The device address byte consists of five fixed bits (01010), followed by two address bits (AD0 and AD1), and a read/write bit (X). The command byte includes three zero bits, followed by RST and PD bits, and three channel address bits (A2-A0). The response signal (ACK) is sent after each byte transfer to confirm successful reception.
The MAX521 is interfaced with a microcontroller using P1.6 and P1.7 for I2C communication. All reference voltages are connected to +5V, ensuring the output voltage range remains between 0 and +5V. The device address is set to 01B, and the system has been successfully implemented in circuits requiring multiple DAC conversions. This solution offers a cost-effective and efficient alternative to traditional parallel DACs, making it ideal for intelligent device development.