MAX1760HEUB+T中文资料(8)

Step-Up DC-DC Converter

0.8A, Low-Noise, 1MHz,Reference

where VThe MAX1760 has an internal 1.250V ±1% reference.FB, the boost-regulator feedback set point, is1.24V.

Connect a 0.22µF ceramic bypass capacitor from REFto GND within 0.2in (5mm) of the REF pin. REF canSetting the Switch Current Limit

source up to 50µA of external load current.

and Soft-Start

The ISET pin adjusts the inductor current limit andimplements soft-start. With ISET connected to REF, theSetting the Output Voltages

inductor current limits at 1.25A. With ISET connected toFor a fixed 3.3V output, connect FB to GND. To seta resistive divider set from REF to GND, the current limitother output voltages between 2.5V and 5.5V, connectis reduced according to:

a resistor voltage-divider to FB from OUT to GND(Figure 3). The input bias current into FB is <20nA,allowing large-value divider resistors without sacrificingILIM = 1.25A VISET

accuracy. Connect the resistor voltage-divider as close 1.25V

to the IC as possible, within 0.2in (5mm) of FB. ChooseImplement soft-start by placing a resistor from ISET toR2 of 270k or less, then calculate R1 using:

REF and a capacitor from ISET to GND. In shutdown,ISET is discharged to GND through an on-chip 100k resistor. At power-up, ISET is 0V and the LX current iszero. As the capacitor voltage rises, the currentincreases and the output voltage rises. The soft-start

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MAX1760