ADC0804 8-Bit Analog-to-Digital Converter IC – 20-Pin DIP

The ADC0804 is an 8-bit successive-approximation Analog-to-Digital Converter (ADC) designed to convert an analog voltage signal into an 8-bit digital value that can be processed by a microcontroller, microprocessor, or digital logic circuit.

It provides a simple 8-bit parallel data interface, differential analog inputs, an adjustable voltage-reference input, and an onboard clock-generator circuit. The ADC0804 can be interfaced with microprocessors or configured for standalone conversion applications.

Technical Specifications

• Model: ADC0804
• Device Type: Analog-to-Digital Converter (ADC)
• ADC Architecture: Successive Approximation (SAR)
• Resolution: 8-Bit
• Number of Input Channels: 1
• Analog Input Type: Differential
• Digital Output: 8-Bit Parallel
• Typical Supply Voltage: 5V DC
• Operating Supply Range: 4.5–6.3V DC depending on device version
• Standard Analog Input Range: 0–5V with 5V supply
• Conversion Time: Approx. 100µs nominal; datasheet timing depends on clock conditions
• Maximum Sample Rate: Approx. 10kSPS
• Typical Clock Frequency: 640kHz
• Clock Generator: On-Chip, requires external timing components when used in RC-clock configuration
• Voltage Reference: Adjustable through VREF/2
• Control Interface: CS, RD, WR and INTR
• Logic Compatibility: TTL / MOS-Compatible Control Interface
• Output Type: Tri-State Digital Outputs
• Package: 20-Pin DIP for common through-hole version
• No Zero Adjustment Required: Yes

8-Bit Analog-to-Digital Conversion

The ADC0804 converts an analog input voltage into one of 256 digital levels, represented by an 8-bit binary output from:

00000000 to 11111111

With the standard 0–5V input range, each digital step represents approximately:

5V ÷ 256 ≈ 19.5mV per step

The effective measurement range can also be adjusted using the VREF/2 input, allowing better use of the available 8-bit resolution when measuring a smaller analog-voltage range.

Differential Analog Input

The ADC0804 provides two analog input pins:

VIN(+) – Positive Analog Input
VIN(−) – Negative Analog Input

For simple single-ended measurements, VIN(−) can typically be referenced to analog ground while the signal is applied to VIN(+).

The differential-input arrangement can also be useful for offsetting the analog zero point and improving common-mode performance in suitable circuits.

Parallel Digital Output

After conversion, the ADC0804 presents the result through eight parallel digital output lines: DB0 to DB7.

This parallel architecture allows all eight bits of the converted value to be read simultaneously.

Control signals including CS, RD, WR and INTR are used to start conversions, monitor conversion completion, and read the resulting digital data.

Clock Operation

The ADC0804 includes an on-chip clock generator, but external timing components are normally used to establish the conversion clock when operating with the internal RC oscillator configuration.

An external clock source can also be used when required by the application.

Conversion speed depends on the selected clock frequency.

Applications

Ideal for analog sensor interfacing, voltage measurement, data-acquisition circuits, microprocessor systems, educational electronics, instrumentation, analog-to-digital conversion experiments, industrial control projects, legacy computer interfaces, and digital measurement systems.

It is particularly useful when a digital system requires an external ADC with a straightforward 8-bit parallel interface.

Important Note

The ADC0804 is an 8-bit parallel ADC, not an I2C or SPI converter. It therefore requires multiple GPIO/data lines when connected directly to a modern microcontroller.

Also note that ADC0804 variants from different manufacturers may have differences in operating temperature, accuracy, package, and electrical specifications. Check the exact manufacturer marking when these parameters are critical.

For modern projects requiring higher resolution or fewer interface pins, an I2C or SPI ADC may be more convenient, but the ADC0804 remains useful for educational, legacy, and parallel-interface applications.

Package Includes

1 × ADC0804 8-Bit Analog-to-Digital Converter IC