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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX878 Datasheet

Step-Up/Step-Down DC-DC Converters

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19-0204; Rev 1; 5/94
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
5V/3.3V/3V/Adjustable-Output,
Step-Up/Step-Down DC-DC Converters
_______________General Description
The MAX877/MAX878/MAX879 are pulse-skipping, step-
up/step-down DC-DC converters that provide a regulated
output from inputs both above and below the output. They
require only three external components—an inductor
(typically 22µH) and two filter capacitors.
The MAX877 delivers a regulated 5V output from 2.5V to
6.2V inputs. The MAX878 generates pin-selectable volt-
ages of 3.0V or 3.3V from 1.5V to 6.2V inputs. The MAX879
output can be adjusted from 2.5V to 6V via an external
resistor divider from 2.5V to 6.2V inputs.
A unique high-power, internal, synchronous rectifier design
(Active Rectifier™) enables the devices to regulate in a
switched linear mode if the input voltage is higher than the
desired output voltage. When the input voltage falls below
the output voltage, the MAX877/MAX878/MAX879 will
smoothly switch into a pulse-skipping boost mode and
step up from input voltages as low as 1V. In shutdown, the
active rectifier disconnects the output from the source. This
stops the current drain from input to output associated with
conventional step-up converters.
High-frequency operation (up to 300kHz) allows the use of
small surface-mount inductors. Supply current is 195µA
under no load, and only 20µA in shutdown mode. For 1-cell
(1V) step-up converters with similar performance and the
same pinout, refer to the MAX777/MAX778/MAX779 data
sheet.
________________________Applications
Two or Three NiCd Cells to 3V/3.3V Conversion
Three or Four Alkaline Cells to 5V Conversion
One Lithium Cell to 3V/3.3V Conversion
Pagers
Palmtop and Notebook Computers
Battery-Powered and Hand-Held Instruments
__________________Pin Configuration
____________________________Features
o Regulates from Inputs Above & Below the Output
o 1V to 6.2V Supply-Voltage Range
o Internal 1A Active Rectifier with Input-to-Output
Disconnect in Shutdown
o Up to 210mA Load Currents, Guaranteed
o 85% Efficiency
o Only 3 External Components
o Adjustable Current Limit
o 195µA Quiescent Supply Current
o 20µA Shutdown Supply Current
o 3V/3.3V/5V and Adjustable Output Voltage Versions
o Available in 8-Pin DIP and SO Packages
______________Ordering Information
PART
MAX877CPA
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
MAX877CSA
MAX877C/D
MAX877EPA
MAX877ESA
MAX877MJA
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP
Ordering Information continued on last page.
* Contact factory for dice specifications.
__________Typical Operating Circuit
INPUT
1.8V TO 6.2V
TOP VIEW
ILIM 1
IN 2
AGND 3
PGND 4
MAX877
MAX878
MAX879
8 N.C. (MAX877)*
7 SHDN
6 OUT
5 LX
DIP/SO
22µF
ON/OFF
2
IN
1 ILIM MAX878
5
LX
7
SHDN
6
OUT
SEL PGND AGND
843
22µH
OUTPUT
3.3V
210mA
100µF
* SEL (MAX878), FB (MAX879)
™ Active Rectifier is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX878 Datasheet

Step-Up/Step-Down DC-DC Converters

No Preview Available !

5V/3.3V/3V/Adjustable-Output,
Step-Up/Step-Down DC-DC Converters
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (IN to PGND) .......................................0V to +7V
Output Short-Circuit Duration to PGND, AGND (Note 1)....30sec
Voltage Applied to:
LX (switch off).......................................................-0.3V to +7V
OU(Ts,wS–—iHt—cDh—No.n..).......................................................................3..0..s..e..c...s..h..o..r.t..t-o0.I3NVotroO+U7VT
FB ..........................................................-0.3V to (OUT + 0.3V)
AGND to PGND ........................................................-0.3V, +0.3V
Reverse Battery Current....................................................900mA
Continuous Power Dissipation (TA = +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW
SO (derate 5.88mW/°C above +70°C) .........................471mW
CERDIP (derate 8.00mW/°C above +70°C) .................640mW
Operating Temperature Ranges:
MAX87_C_A ........................................................0°C to +70°C
MAX87_E_A .....................................................-40°C to +85°C
MAX87_MJA ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1: The output may be shorted to ground continuously if the package power dissipation is not exceeded.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V IN = 2.7V, I LOAD = 0mA, LX = 22 µH, C OUT = 100µF, –S—H—D—N and ILIM connected to IN, AGND connected to PGND,
TA = TMIN to TMAX, typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
ILOAD = 0mA, TA = +25°C
Minimum Start-Up Voltage
(Notes 2, 6)
MAX877/MAX879 (VOUT = 5V), 0mA < ILOAD < 180mA,
TA = +25°C
MAX878/MAX879 (VOUT = 3.3V), 0mA < ILOAD < 120mA,
TA = +25°C
Maximum Operating Voltage
(Notes 2, 3)
Output Voltage
(MAX879 set to 5V)
(Note 3)
MAX877C/MAX879C: 0mA ILOAD 240mA,
2.7V VIN 6.2V;
MAX877E/MAX879E: 0mA ILOAD 220mA,
2.7V VIN 6.2V;
MAX877M/MAX879M: 0mA ILOAD 180mA,
2.7V VIN 6.2V
MAX878C/MAX879C: 0mA ILOAD 210mA,
1.8V VIN 6.2V;
Output Voltage
(MAX879 set to
3.3V)
(Note 3)
SEL = 0V
MAX878E/MAX879E: 0mA ILOAD 200mA,
1.8V VIN 6.2V;
MAX878M/MAX879M: 0mA ILOAD 180mA,
1.8V VIN 6.2V
MAX878C: 0mA ILOAD 210mA, 1.8V VIN 6.2V;
SEL = Open MAX878E: 0mA ILOAD 200mA, 1.8V VIN 6.2V;
MAX878M: 0mA ILOAD 180mA, 1.8V VIN 6.2V
Output Voltage Range
Efficiency
No-Load Supply Current
Shutdown Supply Current
–S—H—D—N– Bias Current
MAX879, ILOAD = 0mA (Note 4)
MAX877/MAX879 (VOUT = 5V), ILOAD = 100mA, VIN = 4V
MAX878/MAX879 (VOUT = 3.3V), ILOAD = 100mA, VIN = 2.5V
ILOAD = 0mA (switch off)
–S—H—D—N– = 0V
0V < –S—H—D—N–< VIN
VIN < –S—H—D—N– < 5V
MAX87_C, MAX87_E
MAX87_M
MIN
6.2
4.80
3.17
2.88
2.5
TYP
1
5.00
3.30
3.00
85
82
195
20
20
15
12
MAX UNITS
2.5 V
1.5
V
5.20
V
3.43
V
3.12
6.0 V
%
310 µA
30
µA
35
100 nA
40 µA
2 _______________________________________________________________________________________
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Part Number MAX878
Description Step-Up/Step-Down DC-DC Converters
Maker Maxim
Total Page 12 Pages
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