MAXREFDES1004: -73V to -35V input, 5V/100mA output, Boost converter

MAXREFDES1004 is used to achieve negative voltage to positive voltage conversion. It can support the input voltage range from -73V to -35V and output 5V@100mA to meet the design requirements of most non-isolated communication power supplies. This reference design uses the MAX668 fixed-frequency, pulse-width modulation (PWM), current-mode DC-DC controller. The MAX668 is used in wide-range input DC-DC conversion applications, including boost, SEPIC, flyback, and isolated output power supplies. It can output 20W or higher power, and the conversion efficiency is higher than 90%. The 1.8V to 28V input voltage range supports a wide range of battery or AC powered inputs. The advanced BiCMOS design features low operating current (220µA), adjustable operating frequency (100kHz to 500kHz), soft-start, and a sync input allows the MAX668 oscillator to be synchronized with an external clock.

The MAX668 operates at a minimum voltage of 3V and can be connected in a bootstrap or non-bootstrap (IC is powered by the input supply or other power supply) configuration. In non-bootstrap configuration, there is no limit on the output voltage.

Key Features

• -73V to -35V input, 5V output, output current up to 100mA

• 20mV output voltage ripple

• 1250kHz operating frequency

• 220µA quiescent current, 70% peak efficiency

• soft start

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Design, build and test

This reference design introduces the hardware shown in Figure 1 and provides detailed technical guidance for designing a negative-input, positive-output boost converter using Maxim's MAX668 current-mode controller. This power supply design has been fully tested, please refer to the detailed introduction.

design resources