19-0211; Rev 4; 5/96
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
_______________General Description
____________________________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
The MAX856–MAX859 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 are greater than 85%. Typical quies-
cent supply current is 25µA (1µA in shutdown).
♦ 125mA and 500mA Switch-Current Limits Permit
Use of Low-Cost Inductors
♦ Up to 500kHz Switching Frequency
♦
1.5% Reference Tolerance Over Temperature
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.
♦ Low-Battery Detector (LBI/LBO)
♦ 8-Pin SO and µMAX Packages
______________Ordering Information
PART
TEMP. RANGE
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
PIN-PACKAGE
MAX856CSA
MAX856CUA
MAX856C/D
MAX856ESA
MAX856MJA
MAX857CSA
MAX857CUA
MAX857C/D
MAX857ESA
MAX857MJA
8 SO
8 µMAX
Dice*
________________________Applications
3.3V to 5V Step-Up Conversion
Palmtop Computers
8 SO
†
8 CERDIP
8 SO
Portable Data-Collection Equipment
Personal Data Communicators/Computers
Medical Instrumentation
2-Cell & 3-Cell Battery-Operated Equipment
Glucose Meters
8 µMAX
Dice*
8 SO
†
8 CERDIP
Ordering Information continued at end of data sheet.
* Dice are tested at T = +25°C only.
A
__________Typical Operating Circuit
†
Contact factory for availability.
INPUT
__________________Pin Configuration
0.8V TO V
OUT
TOP VIEW
OUTPUT
5V AT 100mA
OR
1
2
3
4
8
7
6
5
SHDN
3/5
LX
47µH
GND
3.3V AT 125mA
MAX856
MAX858
OUT
LBI
REF
SHDN
ON/OFF
LX
1N5817
LBO
68µF
MAX856
SO/µMAX
3/5
LBI
OUT
3V/5V SELECT
LOW-BATTERY
DETECTOR
INPUT
1
2
3
4
8
7
6
5
SHDN
FB
LX
GND
LOW-BATTERY
DETECTOR OUTPUT
MAX857
MAX859
REF
LBO
OUT
LBI
REF
LBO
GND
SO/µMAX
________________________________________________________________ Maxim Integrated Products
1
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