The LM2797/98 is an efficient step-down switched capacitor voltage converter that produces a regulated low-voltage rail of 120mA from an input range of 2.6V to 5.5V. It utilizes multiple fractional gain configurations to maximize conversion efficiency across the input voltage and output current ranges. The LM2797/98 also features input voltage and output voltage monitoring. It is ideal for Li-Ion and other battery powered designs, requiring minimal external components with no inductors. The LM2797/98 incorporates short-circuit protection, over-temperature protection, and soft-start circuitry to prevent excessive inrush currents.
The LM2797 and LM2798 are switched‑capacitor step‑down DC/DC converters that provide a regulated low‑voltage rail (1.5 V, 1.8 V or 2.0 V) from a 2.6 V‑5.5 V input while drawing only a few microamps in idle. They use two 1 µF flying capacitors and two 10 µF bypass capacitors, eliminating the need for inductors, and include input‑voltage (BATOK) and output‑voltage (POK) monitoring pins.
The device features short‑circuit and over‑temperature protection, soft‑start, and gain‑hopping to maintain high efficiency (up to 90 %). Turn‑on times differ between the two parts (LM2797 100 µs, LM2798 400 µs). The parts are supplied in a 10‑pin MSOP package and are intended for battery‑powered designs such as cellular phones, pagers, and handheld instrumentation.
| Output voltage options | 1.5 V ±6 %, 1.8 V ±5 %, 2.0 V ±5 % |
|---|---|
| Maximum output current | 120 mA |
| Input voltage range | 2.6 V to 5.5 V |
| Turn‑on time (LM2797) | 100 µs |
| Turn‑on time (LM2798) | 400 µs |
| Supply current (unloaded) | 35 µA |
| Supply current (shutdown) | 0.1 µA |
| Efficiency | up to 90 % |
| Package | 10‑Pin MSOP (MSOP‑10) |
The LM2797 turns on in 100 µs.
The device enters shutdown when the EN pin is low, drawing virtually no supply current.