19-0211; Rev 4; 5/96
KIT
ATION
EVALU
ABLE
AVAIL
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
The MAX856–MAX859 are high-efficiency, CMOS, stepup, DC-DC switching regulators for small, low input voltage 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 are greater than 85%. Typical quiescent supply current is 25µA (1µA in shutdown).
The MAX856–MAX859 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.
________________________Applications
3.3V 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 Meters
__________Typical Operating Circuit
INPUT
0.8V TO VOUT
____________________________Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
0.8V to 6.0V Input Supply Voltage
0.8V Typ Start-Up Supply Voltage
85% Efficiency at 100mA
25µA Quiescent Current
1µA 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 µMAX Packages
______________Ordering Information
PART
TEMP. RANGE
MAX856CSA
MAX856CUA
MAX856C/D
MAX856ESA
MAX856MJA
MAX857CSA
MAX857CUA
MAX857C/D
MAX857ESA
MAX857MJA
PIN-PACKAGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-55°C to +125°C
8 SO
8 µMAX
Dice*
8 SO
8 CERDIP†
8 SO
8 µMAX
Dice*
8 SO
8 CERDIP†
Ordering Information continued at end of data sheet.
* Dice are tested at TA = +25°C only.
† Contact factory for availability.
__________________Pin Configuration
TOP VIEW
47µH
ON/OFF
SHDN
OUTPUT
5V AT 100mA
OR
3.3V AT 125mA
LX
1N5817
68µF
SHDN
1
8
LX
3/5
2
7
GND
6
OUT
5
LBI
REF 3
LBO 4
MAX856
3V/5V SELECT
LOW-BATTERY
DETECTOR
INPUT
3/5
SO/µMAX
OUT
SHDN
LBI
REF
MAX856
MAX858
GND
LBO
LOW-BATTERY
DETECTOR OUTPUT
1
8
LX
FB
2
7
GND
6
OUT
5
LBI
REF 3
MAX857
MAX859
LBO 4
SO/µMAX
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX856–MAX859
_______________General Description
