Buck Controllers Maintain Current-sharing Accuracy

Apr 6, 2005 11:42 AM

From Maxim Integrated Products, the MAX5060/MAX5061 PWM buck controllers enable the design of high-output-current, power supplies with a minimum number of external components. Internal voltage regulators allow the controllers to operate from a 5-V, 12-V or 24-V supply and produce an adjustable output voltage ranging from 0.6 V to 5.5 V. The MAX5060/MAX5061 are suited for applications requiring up to 30 A of output current. Multiple dc-dc controller modules can be paralleled to achieve higher output currents.

Both devices employ average-current-mode control, which allows designers to achieve current-limiting as well as current-sharing accuracy of typically ±10%. This capability results in a small inductor and small or fewer external MOSFETs. An external current-sense resistor ensures that ±10% (typical) current-sharing accuracy is maintained between paralleled modules. The current-sense threshold for both devices is only 25 mV, which reduces power dissipation in the sense resistor and allows use of a small sense resistor. For example, in a 20-A supply, it is possible to use a sense resistor with a 2010 case size.

The MAX5060/MAX5061 also limit reverse-current sinking, thus preventing the main power bus (VBUS) from being pulled down when multiple power-supply modules are paralleled. Both the MAX5060 and MAX5061 include ON/OFF input and external frequency synchronization. Switching frequency is externally programmable from 125 kHz to 1.5 MHz.

The MAX5060 includes additional features such as a clock-output signal to drive a second dc-dc converter 180 degrees out-of-phase, a load-monitoring output voltage proportional to the output current, power-good output, overvoltage protection, and differential remote-sense pins to ensure precise voltage at the load.

Available in a thermally enhanced 28-pin TQFN, the MAX5060 is priced at $1.66 each in 1000-piece quantities. The MAX5061 is available in a 16-pin TSSOP package and priced at $1.44 each in quantities of 1000. A 20-A power-supply evaluation kit is also available.

For more information, visit www.maxim-ic.com.

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