PWM controller takes external reference

Edited by the Electronicstalk editorial team Mar 23, 2004

The Endura ISL6420 is a single-phase synchronous-buck pulsewidth modulation controller with integrated MOSFET drivers.

The Endura ISL6420 is a single-phase synchronous-buck pulsewidth modulation controller with integrated mosfet drivers.

The ISL6420 is ideal for a wide range of applications including core power for FPGAs, ASICs, DSPs, embedded controllers and microprocessors, as well as for Ethernet routers and switchers, distributed DC/DC conversion and tracking external reference buck converters.

In these applications, the ISL6420 provides designers with high performance in a very small package that offers power, thermal and cost efficiencies with space and cost savings.

This new high-performance IC integrates control, protection, monitoring and output adjustment all in one very small 4 x 4mm quad flat no-lead (QFN) package.

A key feature of this PWM controller is its ability to accept an external reference input, thereby allowing multiple regulated power supply rails to track each other.

Another key feature, voltage margining, allows downstream circuitry to be exercised within the full range of voltage tolerance that could occur over the life of the product and can be pre-set to a desired percentage variation to ensure simulation of worst-case conditions.

The ISL6420 also provides a simple single feedback-loop voltage mode control for fast transient response and the output voltage can be precisely regulated to as low as 0.6V, with a maximum tolerance of +/-1.0% over temperature and line voltage variations.

The switching frequency is fully adjustable from 100kHz to 1.4MHz providing a wide range of design applications.

The high frequency end of the range allows designers to realise space and cost savings because smaller and fewer passive filter components are needed.

It also includes a high-performance error amplifier with a 15MHz gain bandwidth product and a 6V/us slew rate that enables high convertor bandwidth for fast transient response and a cleaner DC output.

The PWM duty cycle is not limited and can cover the entire 0 to 100% range as needed.

Soft start can be optimised as desired by selecting the capacitor value from the enable soft-start (EN/SS) pin to ground.

Switching the EN/SS pin to ground disables the controller.

The ISL6420 monitors the output voltage and generates a power-good signal when the soft-start sequence has completed and the output is within regulation.

A built-in overvoltage protection circuit prevents the output voltage from going above typically 115% of the set point.

Protection from over-current conditions is provided by making use of the on-resistance of the upper mosfet, saving the cost of an external current-sense resistor.