Features

• Uses Off-the-Shelf Inductors
• Only 33µH Inductor Required
• Low Cost
• 3-Lead TO-92, SO8, or 8-Pin DIP
• Adjustable or Fixed 5V or 12V Output
• Adjustable or Fixed 5V or 12V Output
• Only Three External Components Required
• 320µA IQ
• 1.6V Minimum Start-Up Voltage
• Logic Controlled Shutdown

Typical Application

Description

The LT1109 is a simple step-up DC/DC converter. Avail-able in 8-pin SO, 3-lead TO-92 (fixed output only) or miniDIP packages, the devices require only three external components to construct a complete DC/DC converter. Current drain is just 320uA at no load, making the device ideal for cost-sensitive applications where standby current must be kept to a minimum. The LT1109-5 can deliver 5V at 100mA from a 3V input and the LT1109-12 can deliver 12V at 60mA from a 5V input. The 8-pin versions also feature a logic controlled SHUTDOWN pin that turns off the oscillator when taken low. The gated-oscillator design requires no frequency compensation components. The high frequency 120kHz oscillator permits the use of small surface mount inductors and capacitors. For a 5V to 12V at 120mA converter, see the LT1109A. For a 5V to 12V at 200mA converter with 20µA shutdown current, see the LT1301.