The ADP1821 is a versatile and inexpensive, fixed-frequency step-down DC-to-DC controller from Analog Devices. It features a wide input voltage range of 1 V to 24 V, a wide output voltage range of 0.6 V to 85% of input voltage, a 1% accuracy, 0.6 V reference voltage, all N-channel MOSFET design for low cost, no current sense resistor required, power-good output, programmable soft start with reverse current protection, soft start, thermal overload, current-limit protection, undervoltage lockout, and 10 μA shutdown supply current.
The ADP1821 is a versatile, synchronous PWM step‑down controller that operates from a 3.7 V‑5.5 V internal supply and accepts a wide input voltage range of 1 V to 24 V. It delivers output voltages as low as 0.6 V or up to 85 % of the input voltage, with selectable fixed switching frequencies of 300 kHz or 600 kHz and optional synchronization up to 1.2 MHz. Features include soft‑start, programmable current‑limit, power‑good output, and thermal shutdown.
The handbook covers the full product line, including a detailed specifications table, absolute maximum ratings, pin‑out descriptions, typical performance curves, theory of operation, and design recommendations such as component selection, PCB layout, and application circuits. Revision history and ordering information are also provided.
| Input voltage range (VCC) | 3.7 V – 5.5 V |
|---|---|
| Power‑stage supply voltage | 1 V – 24 V |
| Output voltage range | 0.6 V – 85 % of input |
| Switching frequency options | 300 kHz, 600 kHz, or sync 300 kHz‑1.2 MHz |
| Quiescent current (IVCC + I VCC) | 1 – 2 mA |
| Shutdown current (SHDN) | 10 µA |
| Operating temperature range (junction) | −40 °C – +125 °C |
| Maximum duty cycle (300 kHz) | 85 % (typical) |
The shutdown input draws only 10 µA when the device is off.
It includes soft‑start, reverse‑current protection, programmable current‑limit, power‑good output, thermal shutdown, and undervoltage lockout.