MAX1771CSA Integrated Circuit Chip 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller

12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller

♦ 90% Efficiency for 30mA to 2A Load Currents

♦ Up to 24W Output Power

♦ 110µA Max Supply Current

♦ 5µA Max Shutdown Current

♦ 2V to 16.5V Input Range

♦ Preset 12V or Adjustable Output Voltage

♦ Current-Limited PFM Control Scheme

♦ Up to 300kHz Switching Frequency

♦ Evaluation Kit Available

General Description

The MAX1771 step-up switching controller provides 90% efficiency over a 30mA to 2A load. A unique current-limited pulse-frequency-modulation (PFM) control scheme gives this device the benefits of pulse-widthmodulation (PWM) converters (high efficiency at heavy loads), while using less than 110µA of supply current (vs. 2mA to 10mA for PWM converters).

This controller uses miniature external components. Its high switching frequency (up to 300kHz) allows surface-mount magnetics of 5mm height and 9mm diameter. It accepts input voltages from 2V to 16.5V. The output voltage is preset at 12V, or can be adjusted using two resistors.

The MAX1771 optimizes efficiency at low input voltages and reduces noise by using a single 100mV current-limit threshold under all load conditions. A family of similar devices, the MAX770–MAX773, trades some full-load efficiency for greater current-limit accuracy; they provide a 200mV current limit at full load, and switch to 100mV for light loads.

The MAX1771 drives an external N-channel MOSFET switch, allowing it to power loads up to 24W. If less power is required, use the MAX756/MAX757 or MAX761/MAX762 step-up switching regulators with on-board MOSFETs. An evaluation kit is available. Order the MAX1771EVKIT-SO.

Applications

► Positive LCD-Bias Generators

► Flash Memory Programmers

► High-Power RF Power-Amplifier Supply

► Palmtops/Hand-Held Terminals

► Battery-Powered Applications

► Portable Communicators

ABSOLUTE MAXIMUM RATINGS

Supply Voltage V+ to GND ...............................................................-0.3V, 17V

EXT, CS, REF, SHDN, FB to GND ...................-0.3V, (V+ + 0.3V)

GND to AGND.............................................................0.1V, -0.1V

Continuous Power Dissipation (TA = +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW

SO (derate 5.88mW/°C above +70°C).........................471mW

CERDIP (derate 8.00mW/°C above +70°C).................640mW

Operating Temperature Ranges

MAX1771C_A .....................................................0°C to +70°C

MAX1771E_A ..................................................-40°C to +85°C

MAX1771MJA ................................................-55°C to +125°C

Junction Temperatures

MAX1771C_A/E_A.......................................................+150°C

MAX1771MJA ..............................................................+175°C

Storage Temperature Range .............................-65°C to +160°C

Lead Temperature (soldering, 10sec) .............................+300°C

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.