36 V Output, Sot23, Low-Noise Power Supplies For Varactor Diode Biasing

Maxim Integrated Products introduces the MAX5026/MAX5028 SOT23 step-up DC-DC converters targeted at low-noise varactor diode biasing in TV RF tuners, set-top boxes, satellite receivers, PCI cable modems, and voice-over-cable modems. These devices operate from 3V to 11V input and boost the output up to 36V for MAX5026 (adjustable output version) and 30V for MAX5028 (fixed output version). Up to 12mA output current is possible depending on input voltage and output voltage.

The MAX5026/MAX5028 are designed to operate in discontinuous mode, which reduces switching noise and voltage spikes. In addition, the slew rate at the switch/inductor pin is controlled to further reduce noise. Both devices operate at constant PWM frequency, which provides easy filtering for low-noise applications, allowing high-frequency switching ripple of less than 1 mV peak-to-peak at the output of the power supply. Both devices operate at 500kHz switching frequency, which allows the use of a tiny surface-mount 47 microfarads inductor and a 1 microfarads ceramic output capacitor, resulting in a compact power supply.

Both the MAX5026 and MAX5028 are available in a 6-pin SOT23 package and are rated for operation over the extended-industrial temperature range (-40 degrees Celsius to +85 degrees Celsius).