The **ADC0801** (often referred to as ADC01 series) is a classic 8-bit CMOS successive approximation Analog-to-Digital Converter (ADC). It is designed to interface directly with microprocessors and is widely used for basic sensor data acquisition. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Resolution** | 8 Bits | | **Conversion Time** | 100 microseconds (approx.) | | **Supply Voltage** | 4.5V to 6.3V (Standard 5V) | | **Input Channels** | 1 Differential Channel | | **Error Range** | ±1/4 LSB to ±1 LSB (depending on grade) | | **Clock Source** | On-chip or External | --- ### 2. Main Hardware Components & Pins The ADC0801 uses a 20-pin configuration. Below are the critical electronic sections: #### Control Pins * **CS (Chip Select):** Enables the IC. * **RD (Read):** When low, the digital data is placed onto the output pins. * **WR (Write):** Starts the conversion process on a high-to-low transition. * **INTR (Interrupt):** Goes low when the conversion is finished, signaling the CPU. #### Analog Input Section * **Vin(+) and Vin(-):** Differential analog inputs. This allows for noise rejection or offset adjustments. * **Vref/2:** This pin allows you to set the voltage range. If you provide 1.28V here, the full input range becomes 0 to 2.56V. #### Digital Output Section * **D0 - D7:** The 8-bit parallel output bus representing the converted digital value. --- ### 3. Circuit Block Diagram (Internal) The internal electronics consist of several functional blocks: 1. **Successive Approximation Register (SAR):** The "brain" that compares the analog input against a generated reference to determine each bit. 2. **R-2R Ladder:** A precision resistor network used as a Digital-to-Analog Converter (DAC) inside the chip to compare against the input voltage. 3. **Comparator:** Compares the input voltage to the DAC output. 4. **Tri-state Latches:** Holds the output data so it can be read by a microprocessor bus without interfering with other devices. --- ### 4. Basic Connection Example ```cpp // Typical logic flow for interfacing with a microcontroller: 1. Set CS = 0 (Select Chip) 2. Pulse WR pin (Start conversion) 3. Wait for INTR to go LOW (Conversion complete) 4. Set RD = 0 (Read data) 5. Read pins D0-D7 6. Set RD = 1 and CS = 1 ``` ---