MAX849

Up to 95% Efficiency (see Typical Output Selector Guide below)
3.3V Dual Mode™ or 2.7V to 5.5V Adj. Output
0.7V to 5.5V Input Range
0.15mW Standby Mode
300kHz PWM Mode or Synchronizable
Two-Channel ADC with Serial Output
Power-Good Function

Digital Cordless                                            Phones PCS Phones
Cellular Phones                                       Hand-Held Instruments
Palmtop Computers                              Personal Communicators
Local 3.3V to 5V Supplies

ON1, ON2, OUT, POUT to GND.....................................................-0.3V, +6V
PGND to GND ...........................................................................-0.3V, +0.3V
LX to PGND ...............................................................-0.3V, (VPOUT + 0.3V)
CLK/SEL, DATA, POKIN, REF,
AINSEL, AIN1, AIN2, FB, POK to GND ..........................-0.3V, (VOUT + 0.3V)
Continuous Power Dissipation (TA = +70°C)
Narrow SO (derate 8.7mW/°C above +70°C) ..............................696mW
Operating Temperature Range
MAX848ESE/MAX849ESE .................................................-40°C to +85°C
Junction Temperature....................................................................+150°C
Storage Temperature.....................................................-65°C to +160°C
Lead Temperature (soldering, 10sec) ...........................................+300°C

The MAX848/MAX849 boost converters set a new standard of high efficiency and high integration for noisesensitive power-supply applications, such as portable phones and small systems with RF data links. The heart of the these MAX849 is a synchronous boost-topology regulator that generates a fixed 3.3V output (or 2.7V to 5.5V adjustable output) from one to three NiCd/NiMH cells or one Li-Ion cell.

Synchronous rectification of MAX849 provides a 5% efficiency improvement over similar nonsynchronous boost regulators. In standby mode, pulse-skipping PFM operation keeps the output voltage alive with only 150W quiescent power consumption. Fixed-frequency PWM operation ensures that the switching noise spectrum is limited to the 300kHz fundamental and its harmonics, allowing easy post-filtering noise reduction. For even tighter noise spectrum control, synchronize to a 200kHz to 400kHz external clock.

Battery monitoring of MAX849 is provided by a two-channel, voltage- to-frequency analog-to-digital converter (ADC). One channel is intended for a single-cell battery input (0.625V to 1.875V range), while the other channel is for monitoring higher voltages (0V to 2.5V range).

Two control inputs of MAX849 are provided for push-on, push-off control via a momentary pushbutton switch. Upon power-up, an internal comparator monitors the output voltage to generate a power-good output (POK).

The MAX849 differ only in the current limit of the N-channel MOSFET power switch: 0.8A for the MAX848, and 1.4A for the MAX849.