Power Electronics

PWM Controllers Eliminate Current-Sensing Resistor

The ISL6545 and ISL6545A from Intersil are single-output PWM (pulse-width modulation) controllers. These devices integrate the MOSFET drivers, boot diode and current-sensing functions on a single chip.

The overcurrent function protects the controllers from a shorted output by using the lower MOSFET’s on-resistance, RDS(ON), to monitor the current, enhancing the efficiency of the controllers and reducing cost by eliminating the current-sensing resistor.

The ISL6545 and ISL6545A simplify the implementation of a complete control and protection scheme for a dc-dc step-down converter driving inexpensive N-channel MOSFETs in a synchronous buck topology. Each device features a fixed frequency oscillator (300 kHz for ISL6545; 600 kHz for ISL6545A).

These devices provide a single feedback loop and voltage-mode control with fast transient response. The output voltage can be precisely regulated to as low as 0.6 V with a maximum tolerance of +1.0% over temperature and line-voltage variations.

The error amplifier of the ISL6545 and ISL6545A feature a 20-MHz gain bandwidth product and 9 V/µs slew rate that enables high converter bandwidth for fast transient performance. The resulting PWM duty cycles range from 0% to 100%.

The device operates from a +5-V or +12-V supply voltage for bias. It features an input range of 1.0 V to 12 V. Output voltage is 0.6 V to VIN, and the integrated gate drivers use a VCC of 5 V to 12 V.

The ISL6545 and ISL6545A use a simple single-loop control design for voltage-mode PWM control. The devices are available now in an 8-lead SOIC package. They are priced at $1.00 each and in a 10-lead QFN package, and priced at $1.51 each in 1000-unit quantities.

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