With the Right Converter, a Single Battery Can Power Your Portable Design

Jim Harrison, Maxim Integrated Guest Blogger, Lincoln Technology Communications


Another boost regulator example may be found in the MAX1705 and MAX1706 family of high-efficiency, low-noise, step-up DC-DC converters with an auxiliary linear-regulator output. As discussed previously, 3.6V lithium cells typically require a buck-boost topology to cover their lifetime voltage range. These converters, however, combine boost and linear regulators, and the linear output is a very low-noise supply as well. Using a 300kHz synchronous rectifier PWM boost topology, the ICs can generate a 2.5V to 5.5V output from a battery input, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell. They provide a regulated output over their entire operating voltage range. The MAX1705 has a 1A n-channel MOSFET switch, while the MAX1706 has a 0.5A switch. Minimum VIN is 1.1V and they have a 1μA shutdown mode.

The linear regulator in both devices delivers up to 200mA. An efficiency-enhancing track mode reduces the step-up DC-DC converter output to 300mV above the linear-regulator output. Compared to similar non-synchronous converters, these converters provide 5% better efficiency. To enhance efficiency at light loads, they feature a pulse-frequency-modulation standby mode. Both devices come in a 16-pin QSOP package and have two shutdown-control inputs for push-on/push-off control, along with an uncommitted comparator that can be used as a voltage monitor. To evaluate the ICs for various battery-powered designs, you can check out the MAX1705 evaluation kit.



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