High-Efficiency Step-Up DC-DC Controllers — MAX770-MAX773

The MAX770-MAX773 step-up switching controllers offer 90% efficiency for a 10mA to 1A load. A unique current-limited pulse-frequency modulation (PFM) control scheme enables these devices to benefit from pulse-width modulation (PWM) converters (high efficiency at heavy loads) while using less supply current than 10mA (about 110µA for a 2mA PWM converter).

These ICs use small external components. Their high switching frequency (up to 300kHz) allows for surface mount heights of 5mm and 9mm diameter magnetics.

The MAX770/MAX771/MAX772 operate from an input voltage range of 2V to 16.5V. Output voltages are preset to 5V (MAX770), 12V (MAX771), and 15V (MAX772); they can also be adjusted with two resistors.

The MAX773's input voltage ranges from 3V to 16.5V. For a wider input range, it has an internal shunt regulator that allows unlimited higher input voltages. The MAX773's output can be set to 5V, 12V, or 15V and can also be adjusted with two resistors.

The MAX770-MAX773 drive external N-channel MOSFET switches, allowing them to power loads up to 15W. If more power savings are needed, use the MAX756/MAX757 or MAX761/MAX762 step-up switching regulators with onboard MOSFETs.

characteristic:

● 90% efficiency, 10mA to 1A load current

● Output power up to 15W

● Maximum power supply current 110μA

● Maximum shutdown current 5μA

● 2V to 16.5V input range (MAX770/MAX771/MAX772)

● Internal shunt regulator (MAX773) for high input voltage

● Preset or adjustable output voltage

MAX770: 5V or adjustable

MAX771: 12V or adjustable

MAX772: 15V or adjustable

MAX773: 5V, 12V, 15V, or adjustable

● Current-limited PFM control plan

● 300kHz switching frequency

Typical working circuit:

application:

Battery powered applications

Flash memory programming

● High efficiency DC-DC converter

● Palm computer, handheld terminal

● Portable communication device

● LCD positive bias generator