The LT1109A is a micropower DC/DC converter that can be used as a flash memory VPP generator. It supports 5V and 12V fixed outputs, or an adjustable version. The device uses off-the-shelf inductors, is low cost, and only requires an 8-pin DIP or SOIC package. The no-load current is only 360µA, making it ideal for cost-sensitive applications where standby current must be kept to a minimum. The LT1109A-12 can provide over 150mA of 12V power from a 5V supply, enough to program four flash memory chips simultaneously. The LT1109A-5 can provide up to 110mA of 5V power from a 2V input. The device has a shutdown pin that turns off the oscillator when the pin is low. The gated-oscillator design requires no frequency compensation components. High frequency 120kHz operation permits the use of small surface mount inductors and capacitors.
The LT1109A is a micropower step‑up DC/DC converter that delivers up to 2 W of output power from a 5 V supply while maintaining a standby current of only 360 µA. It operates in burst‑mode and includes a logic‑controlled shutdown pin for low‑power operation.
The document lists absolute maximum ratings, electrical characteristics, typical performance curves, and detailed component‑selection advice for inductors, capacitors, and diodes. Typical applications such as flash‑memory VPP generators and 5 V‑to‑12 V converters are illustrated with schematic examples and recommended part numbers.
| Quiescent current (shutdown) | 360 µA |
|---|---|
| Maximum power dissipation | 300 mW |
| Operating temperature range | 0 °C to 70 °C |
| Input voltage range (recommended) | 2 V to 9 V |
| Output voltage ripple (LT1109A‑5) | 25‑50 mV |
| Oscillator frequency | 105‑120 kHz |
The standby (quiescent) current with the shutdown pin high is 360 µA.
The device is recommended for an input voltage between 2 V and 9 V.
The 1N5818 Schottky diode is the ideal choice for LT1109A circuits.
The oscillator typically runs at about 120 kHz (range 105‑135 kHz).