1.2MHz/2.2MHz Inverting DC/DC Converters in ThinSOT

The LT1931/LT1931A are the industry’s highest power inverting SOT-23 current mode DC/DC converters. Both parts include a 1A integrated switch allowing high current outputs to be generated in a small footprint. The LT1931 switches at 1.2MHz while the LT1931A switches at 2.2MHz. These high speeds enable the use of tiny, low cost capacitors and inductors 2mm or less in height. The LT1931 is capable of generating –5V at 350mA or –12V at 150mA from a 5V supply, while the LT1931A can generate –5V at 300mA using significantly smaller inductors. Both parts are easy pin-for-pin upgrades for higher power LT1611 applications.

The LT1931/LT1931A operate in a dual inductor inverting topology that filters both the input side and output side current. Very low output voltage ripple approaching 1mVP-P can be achieved when ceramic output capacitors are used. Fixed frequency switching ensures a clean output free from low frequency noise typically present with charge pump solutions. The low impedance output remains within 1% of nominal during large load steps. The 36V switch allows VIN to VOUT differential of up to 34V.

The LT1931/LT1931A are available in the 5-lead ThinSOT package.

Applications

* Disk Drive MR Head Bias

* Digital Camera CCD Bias

* LCD Bias

* GaAs FET Bias

* Local Low Noise/Low Impedance Negative Supply

* Fixed Frequency 1.2MHz/2.2MHz Operation

* Very Low Noise: 1mVP-P Output Ripple

* –5V at 350mA from 5V Input

* –12V at 150mA from 5V Input

* Uses Small Surface Mount Components

* Wide Input Range: 2.6V to 16V

* Low Shutdown Current: <1µA

* Low VCESAT Switch: 400mV at 1A

* Pin-for-Pin Compatible with the LT1611

* Low Profile (1mm) ThinSOT™ Package