Datasheet MAX856, MAX857, MAX858, MAX859 (Maxim)

19-0211; Rev 4; 5/96
EVALUATION KIT AVAILABLE 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters MAX856–MAX859 _______________General Description ____________________________Features
The MAX856–MAX859 are high-efficiency, CMOS, step- ♦
0.8V to 6.0V Input Supply Voltage
up, DC-DC switching regulators for small, low input volt- ♦
0.8V Typ Start-Up Supply Voltage
age or battery-powered systems. The MAX856/MAX858 ♦
85% Efficiency at 100mA
accept a positive input voltage between 0.8V and VOUT ♦
25µA Quiescent Current
and convert it to a higher, pin-selectable output voltage of 3.3V or 5V. The MAX857/MAX859 adjustable versions ♦
1µA Shutdown Mode
accept 0.8V to 6.0V input voltages and generate higher ♦
125mA and 500mA Switch-Current Limits Permit
adjustable output voltages in the 2.7V to 6.0V range.
Use of Low-Cost Inductors
Typical efficiencies are greater than 85%. Typical quies- ♦
Up to 500kHz Switching Frequency
cent supply current is 25µA (1µA in shutdown). ♦
±1.5% Reference Tolerance Over Temperature
The MAX856–MAX859 combine ultra-low quiescent supply ♦
Low-Battery Detector (LBI/LBO)
current and high efficiency to give maximum battery life. An ♦
8-Pin SO and µMAX Packages
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
______________Ordering Information
inductors. The MAX856/MAX857 have a 500mA peak inductor current limit. The MAX858/MAX859 have a 125mA
PART TEMP. RANGE PIN-PACKAGE
peak inductor current limit.
MAX856
CSA 0°C to +70°C 8 SO
________________________Applications
MAX856CUA 0°C to +70°C 8 µMAX MAX856C/D 0°C to +70°C Dice* 3.3V to 5V Step-Up Conversion MAX856ESA -40°C to +85°C 8 SO Palmtop Computers MAX856MJA -55°C to +125°C 8 CERDIP† Portable Data-Collection Equipment
MAX857
CSA 0°C to +70°C 8 SO Personal Data Communicators/Computers MAX857CUA 0°C to +70°C 8 µMAX Medical Instrumentation MAX857C/D 0°C to +70°C Dice* 2-Cell & 3-Cell Battery-Operated Equipment MAX857ESA -40°C to +85°C 8 SO Glucose Meters MAX857MJA -55°C to +125°C 8 CERDIP†
Ordering Information continued at end of data sheet.
* Dice are tested at TA = +25°C only.
__________Typical Operating Circuit
† Contact factory for availability. INPUT
__________________Pin Configuration
0.8V TO VOUT TOP VIEW OUTPUT SHDN 1 8 5V AT 100mA LX 47µH OR 2 3/5 7 GND 3.3V AT 125mA MAX856 3 6 ON/OFF SHDN LX REF OUT MAX858 1N5817 4 5 LBO LBI 68µF MAX856
SO/
µ
MAX
3V/5V SELECT 3/5 OUT LOW-BATTERY LBI SHDN 1 8 LX DETECTOR INPUT 2 FB 7 GND LOW-BATTERY MAX857 REF LBO 3 6 GND DETECTOR OUTPUT REF OUT MAX859 4 5 LBO LBI
SO/
µ
MAX ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800