MAX848ESE datasheet(8/16 Pages) MAXIM

8 / 16 page

1-Cell to 3-Cell, High-Power,

Low-Noise, Step-Up DC-DC Converters

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Pin Description

ADC’s Input Channel Selector. Pull low to select AIN1 and drive high to select AIN2.

AINSEL

ADC’s Serial Output. Pulsed output, RZ format. Full scale is fOSC/2 (fCLK/2 in external sync mode). The

DATA output is low when VCLK/SEL = 0V (PFM mode).

DATA

External Clock Input/Regulator’s Switching Mode Selector.

CLK/SEL = low: low-power, low-quiescent PFM mode. Delivers 100mW of output power.

CLK/SEL = high: low-noise, high-power PWM mode, switching at a constant frequency (300kHz).

CLK/SEL = driven with external clock: low-noise, high-power, synchronized PWM mode. The internal

oscillator is synchronized to the external clock (200kHz ~ 400kHz). Turning the DC-DC converter on with

VCLK/SEL = 0V also serves as a soft-start function, since the peak inductor current is limited to 30% of the

nominal value.

CLK/SEL

Source of the Internal N-Channel Power MOSFET. Connect to high-current ground path.

PGND

Drain of the Internal N-Channel Power MOSFET and P-Channel Synchronous Rectifier

Output Sense Input. The IC is powered from OUT. Bypass to GND with a 0.1µF ceramic capacitor. Connect

OUT to POUT through a 10

Ω series resistor.

OUT

Power-Good Comparator Input. Connect to GND for fixed threshold (VOUT x 0.9). To adjust the threshold,

connect to a resistor divider from OUT to GND.

POKIN

Dual Mode DC-DC Converter Feedback Input. Connect to GND for fixed 3.3V output voltage. Connect to

a resistor divider from OUT to GND to adjust the output voltage. Minimize noise coupling from switching

signals to FB.

Power-Good Output. This open-drain output is pulled low when the output voltage (VOUT) drops below

the internally set threshold (fixed threshold), or when the voltage at POKIN drops below VREF (adjustable

threshold).

POK

Ground. Use for low-current ground paths. Connect to PGND with a short trace.

GND

Reference Output. Bypass with a 0.22µF capacitor to GND.

REF

ADC’s Channel 2 Input. Analog input voltage range is 0V to 2.5V.

AIN2

ADC’s Channel 1 Input. Analog input voltage range is 0.625V to 1.875V.

AIN1

FUNCTION

NAME

POUT

Source of the Internal P-Channel Synchronous Rectifier MOSFET. Connect an external Schottky diode from

LX to POUT. Bypass to PGND with a 0.1µF ceramic capacitor as close to the IC as possible.

ON2

OFF Control Input. When ON1 = 0 and ON2 = 1, the IC is off.

ON1

ON Control Input. When ON1 = 1 or ON2 = 0, the IC is on.

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