MAX1760HEUB+T中文资料(6)

Step-Up DC-DC Converter

0.8A, Low-Noise, 1MHz,Figure 1. Functional Diagram

Detailed Description

The MAX1760 is a highly efficient, low-noise power sup-ply for portable RF and hand-held instruments. It com-bines a boost switching regulator, N-channel powerMOSFET, P-channel synchronous rectifier, precisionreference, and shutdown control (Figure 1).

The DC-DC converter boosts a 1-cell to 3-cell batteryvoltage input to a fixed 3.3V or adjustable voltagebetween 2.5V and 5.5V. An external Schottky diode isrequired for output voltages greater than 4V. TheMAX1760 guarantees startup with an input voltage aslow as 1.1V and remains operational down to an inputof just 0.7V. It is optimized for use in cellular phonesand other applications requiring low noise and low qui-escent current for maximum battery life. It featuresfixed-frequency operation at medium and heavy loads,but at light loads, switches only as needed for optimumFigure 2. Standard Application Circuit

efficiency. This device is also capable of constant-fre-quency (1MHz), low-noise PWM operation at all loadStep-Up Converter

currents, or frequency-synchronized PWM operationDuring DC-DC converter operation, the internal N-chan-when connected to an external clock. Table 1 listsnel MOSFET switch turns on for the first part of eachsome typical outputs. Shutdown reduces quiescent cur-cycle, allowing current to ramp up in the inductor andrent to just 1µA. Figure 2 shows the standard applica-store energy in a magnetic field. During the secondtion circuit for the MAX1760.

part of each cycle, the MOSFET turns off and inductorcurrent flows through the synchronous rectifier to the

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MAX1760/MAX1760H