Features: 0.8V to 6.0V Input Supply Voltage
0.8V Typ Start-Up Supply Voltage
85% Efficiency at 100mA
25A Quiescent Current
1A Shutdown Mode
125mA and 500mA Switch-Current Limits Permit
Use of Low-Cost Inductors
Up to 500kHz Switching Frequency
±1.5% Reference Tolerance Over Temperature
Low-Battery Detector (LBI/LBO)
8-Pin SO and MAX PackagesApplication3.3V to 5V Step-Up Conversion
Palmtop Computers
Portable Data-Collection Equipment
Personal Data Communicators/Computers
Medical Instrumentation
2-Cell & 3-Cell Battery-Operated Equipment
Glucose MetersPinout
SpecificationsSupply Voltage (OUT to GND) .....................................-0.3V, +7V
Switch Voltage (LX to GND) ........................................-0.3V, +7V
SHDN , LBO to GND.....................................................-0.3V, +7V
LBI, REF, 3/5, FB to GND .............................-0.3V, (VOUT + 0.3V)
Reference Current (IREF) ..................................................2.5mA
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
MAX (derate 4.1mW/°C above +70°C) .......................330mW
CERDIP (derate 8.00mW/°C above +70°C) ..................640mW
Reverse Battery Current (TA +45°C, Note 1)...................750mA
Operating Temperature Ranges
MAX85_C_ _ .......................................................0°C to +70°C
MAX85_E_ _ .....................................................-40°C to +85°C
MAX85_MJA ....................................................-55°C to +125°C
Junction Temperature ....................................................+150°C
Storage Temperature Range ..........................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
DescriptionThe MAX857 are high-efficiency, CMOS, step- up, DC-DC switching regulators for small, low input volt- age or battery-powered systems. The MAX856/MAX858 accept a positive input voltage between 0.8V and VOUT and convert it to a higher, pin-selectable output voltage of 3.3V or 5V. The MAX857/MAX859 adjustable versions accept 0.8V to 6.0V input voltages and generate higher adjustable output voltages in the 2.7V to 6.0V range. Typical efficiencies of MAX857 are greater than 85%. Typical quies- cent supply current is 25A (1A in shutdown).
The MAX857 combine ultra-low quiescent supply current and high efficiency to give maximum battery life. An internal MOSFET power transistor permits high switching frequencies. This benefit, combined with internally set peak inductor current limits, permits the use of small, low-cost inductors. The MAX856/MAX857 have a 500mA peak inductor current limit. The MAX858/MAX859 have a 125mA peak inductor current limit.
MAX857 Data Sheet
