Intersil DC/DC converter optimized for RF power amplifiers

6th October 2008

ES Admin

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Datasheet

Intersil has announced a DC/DC converter for RF power amplifiers that provides the industry’s fastest start up from standby mode with very low current and excellent transient load response. The ISL9109 is a 1.6MHz synchronous step-down regulator designed to resolve the inefficiencies often seen with mobile RF power amps, particularly at low output levels. The device incorporates power switches that deliver 1.5A output and features a standby mode that enables rapid startup.

This rapid startup is achieved even though the part draws only 22 microamps standby current (typical) and provides the highest possible light load efficiency while reducing power draw and maximizing battery. When powered from a Li-ion battery, the ISL9109 operates at 90-95% efficiency in powering an RF PA.

The ISL9109’s supply voltage ranges from 2.7V to 5.5V enable designers to use a single Li+ cell, three NiMH cells or a regulated 5V input. The ISL9109’s 1.6MHz pulse-width modulation (PWM) switching frequency also allows the use of small external components. When in standby, the IC’s band-gap reference is powered up, which assists in a rapid power-up when the EN (enable) pin is reasserted high.

Other features of the ISL9109 include soft-start, overcurrent protection and thermal shutdown. In addition, its small 2mm x 3mm DFN form factor saves space in any cell phone or modem card design. The complete converter occupies less than one centimetre squared.