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19-1798; Rev 0; 12/00
Low Supply Current, Step-Up DC-DC Converters
with True-Shutdown
General Description
The MAX1795/MAX1796/MAX1797 are high efficiency
step-up DC-DC converters intended for small portable
hand-held devices. These devices feature Maxim’s
True-Shutdown™ circuitry, which fully disconnects the
output from the input in shutdown, improves efficiency,
and eliminates costly external components. All three
devices also feature Maxim’s proprietary LX-damping
circuitry for reduced EMI in noise-sensitive applica-
tions. For additional in-system flexibility, a battery moni-
toring comparator (LBI/LBO) remains active even when
the DC-DC converter is in shutdown.
The input voltage range is +0.7V to VOUT, where VOUT
can be set from +2V to +5.5V. Startup is guaranteed
from +0.85V. The MAX1795/MAX1796/MAX1797 have a
preset, pin-selectable 5V or 3.3V output. The output
can also be adjusted to other voltages, using two exter-
nal resistors. The three devices differ only in their cur-
rent limits, allowing optimization of external components
for different loads: The MAX1795, MAX1796, and
MAX1797 have current limits of 0.25A, 0.5A, and 1A,
respectively. All devices are packaged in a compact 8-
pin µMAX package that is only 1.09mm tall and half the
size of an 8-pin SO.
________________________Applications
Portable Digital Audio Players
PDAs/Palmtops
Wireless Handsets
Portable Terminals
Features
o >95% Efficiency
o True-Shutdown Circuitry
Output Disconnects from Input in Shutdown
No External Schottky Diode Needed
o 25µA Quiescent Supply Current
o Low-Noise Antiringing Feature
o LBI/LBO Comparator Enabled in Shutdown
o 2µA Shutdown Current
o 8-Pin µMAX Package
PART
MAX1795EUA
MAX1796EUA
MAX1797EUA
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
True-Shutdown is a trademark of Maxim Integrated Products.
Pin Configuration
TOP VIEW
LBI 1
FB 2
LBO 3
SHDN 4
MAX1795
MAX1796
MAX1797
µMAX
8 BATT
7 OUT
6 LX
5 GND
Typical Operating Circuit
IN
0.7V TO
5.5V
OFF
ON
BATT LX
LBI
MAX1795
MAX1796
OUT
MAX1797 FB
LBO
SHDN
GND
OUT
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

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Low Supply Current, Step-Up DC-DC Converters
with True-Shutdown
ABSOLUTE MAXIMUM RATINGS
OUT, LX, SHDN, LBI, LBO, BATT to GND................-0.3V to +6V
FB .............................................................-0.3V to (VOUT + 0.3V)
ILX, IOUT..............................................................................±1.5A
Output Short-Circuit Duration ...................................................5s
Continuous Power Dissipation
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
(VBATT = +2V, OUT = FB (VOUT = +3.3V), SHDN = LBI = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
Minimum Input Voltage
SYMBOL
CONDITIONS
After startup
MIN TYP MAX UNITS
0.7 V
Operating Voltage
Startup Voltage
Startup Voltage Tempco
Output Voltage
VBATT
(Note 1)
TA = +25°C, RL = 3k
VOUT
FB = OUT
FB = GND
1.0 5.5 V
0.85 1.0
V
-2.2 mV/°C
3.17 3.3 3.43
4.80 5.0 5.20
V
Adjustable Output Voltage
Range
2.0 5.5 V
Steady-State Output Current
IOUT
BATT = +2V,
FB = OUT
(VOUT = +3.3V)
BATT = +2V,
FB = GND
(VOUT = +5.0V)
MAX1795
MAX1796
MAX1797
MAX1795
MAX1796
MAX1797
100 180
200 300
400 550
50 120
100 200
250 370
mA
Feedback Set-Point Voltage
(Adjustable Mode)
VFB VOUT = +2V to +5.5V
1.20 1.24 1.28
V
Feedback Input Current
Internal NFET, PFET On-
Resistance
LX Switch Current Limit (NFET
only)
LX Leakage Current
IFB
RDS(ON)
ILIM
ILEAK
VFB = +1.24V
VOUT = +3.3V,
ILX = 100mA
NFET
PFET
MAX1795
MAX1796
MAX1797
VLX = 0 and +5.5V, VOUT = +5.5V
4 100 nA
0.17 0.3
0.27 0.45
0.2 0.25 0.35
0.4 0.5 0.625 A
0.8 1.0 1.25
0.2 µA
Synchronous Rectifier Turn-Off
Current Limit
25 mA
Damping Switch On-Resistance
Operating Current into OUT
(Note 2)
RDAMP
VFB = +1.4V
100 200 400
25 45
µA
2 _______________________________________________________________________________________

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Low Supply Current, Step-Up DC-DC Converters
with True-Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = +2V, OUT = FB (VOUT = +3.3V), SHDN = LBI = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are
TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Operating Current into BATT
Shutdown Current into BATT
LX Switch MaxImum On-Time
LX Switch Minimum Off-Time
LBI Threshold Voltage Falling
LBI Hysteresis
tON
tOFF
VLBI
VFB = +1.4V, VLBI = +1V
SHDN = BATT, VLBI = +1V
VFB = +1V, if current limit not reached
VFB = +1V
VBATT = +2V
VBATT = LBI
3
0.8
0.8
0.875
2
2
4
1
0.85
0.925
25
4
4
5
1.2
0.90
0.975
µA
µA
µs
µs
V
mV
LBI Input Current
ILBI VLBI = +0.8V
9 100 nA
LBO Low Output Voltage
VBATT = VLBI = +0.975V,
sinking 20µA (50typ)
VBATT = VLBI = +1.1V,
sinking 100µA (25typ)
0.1
V
0.1
LBO Off-Leakage Current
VLBO = +5.5V
1 100 nA
SHDN Input Voltage
VIL
VIH
0.8
VBATT
0.2
VBATT
V
Shutdown Input Current
VSHDN = 0 and +5.5V
100 nA
ELECTRICAL CHARACTERISTICS
(VBATT = +2V, OUT = FB (VOUT = +3.3V), SHDN = LBI = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
Operating Voltage
Output Voltage
Adjustable Output Voltage
Range
Steady-State Output Current
(Note 1)
Feedback Set-Point Voltage
(Adjustable Mode)
Feedback Input Current
SYMBOL
VBATT
VOUT
Note 1
FB = OUT
FB = GND
CONDITIONS
IOUT
VFB
IFB
FB = OUT
(VOUT = +3.3V)
FB = GND
(VOUT = +5.0V)
VOUT = +2V to +5.5V
VFB = +1.25V
MAX1795
MAX1796
MAX1797
MAX1795
MAX1796
MAX1797
MIN
1.0
3.13
4.75
2.0
100
200
400
60
125
250
1.19
MAX
5.5
3.47
5.25
5.5
1.29
100
UNITS
V
V
V
mA
V
nA
_______________________________________________________________________________________ 3

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Low Supply Current, Step-Up DC-DC Converters
with True-Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = +2V, OUT = FB (VOUT = +3.3V), SHDN = LBI = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
Internal NFET, PFET On-
Resistance
LX Switch Current Limit (NFET
only)
LX Leakage Current
Damping Switch On-Resistance
Operating Current into OUT
(Note 2)
Operating Current into BATT
Shutdown Current into BATT
LX Switch Maximum On-Time
LX Switch Minimum Off-Time
LBI Threshold Voltage
LBI Input Current
LBO Low Output Voltage
LBO Off-Leakage Current
SHDN Input Voltage
Shutdown Input Current
SYMBOL
RDS(ON)
ILIM
ILEAK
RDAMP
CONDITIONS
VOUT = +3.3V,
ILX = 100mA
NFET
PFET
MAX1795
MAX1796
MAX1797
VLX = 0 and +5.5V, VOUT = +5.5V
VFB = +1.4V
tON
tOFF
VLBI
ILBI
VFB = +1.4V, VLBI = +1V
SHDN = BATT, VLBI = +1V
VFB = +1V, if current limit not reached
VFB = +1V
VBATT = +2V
VBATT = LBI
VLBI = +0.8V
VBATT = VLBI = +0.975V,
sinking 20µA (50typ)
VBATT = VLBI = +1.1V,
sinking 100µA (25typ)
VLBO = +5.5V
VIL
VIH
VSHDN = 0 and +5.5V
MIN
0.19
0.35
0.8
100
2.75
0.7
0.8
0.875
0.8
VBATT
MAX
0.3
0.45
0.37
0.7
1.32
400
45
4
4
5.25
1.3
0.90
0.975
100
0.1
0.1
100
0.2
VBATT
100
UNITS
A
µA
µA
µA
µA
µs
µs
V
nA
V
nA
V
nA
Note 1: Operating Voltage: Since the regulator is bootstrapped to the output, once started it will operate down to a 0.7V input.
Note 2: Device is bootstrapped (power to IC comes from OUT). This correlates directly with the actual battery supply current.
Note 3: Specifications to -40°C are guaranteed by design, not production tested.
4 _______________________________________________________________________________________

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Low Supply Current, Step-Up DC-DC Converters
with True-Shutdown
Typical Operating Characteristics
(L = 22µH, CIN = 47µF, COUT = 47µF, TA = +25°C, unless otherwise noted.)
MAX1795
EFFICIENCY vs. LOAD CURRENT (+5V)
100
VBATT = +3.6V
90
80
70
VBATT = +2.4V
VBATT = +1.2V
60
50
40
30
20
10
0
0.1
1 10 100
LOAD CURRENT (mA)
1000
MAX1795
EFFICIENCY vs. LOAD CURRENT (+3.3V)
100
VBATT = +2.4V
90
80
70 VBATT = +1.2V
60
50
40
30
20
10
0
0.1
L = 10µH
1 10 100
LOAD CURRENT (mA)
1000
MAX1796
EFFICIENCY vs. LOAD CURRENT (+5V)
100
VBATT = +3.6V
90
80
70
VBATT = +2.4V
VBATT = +1.2V
60
50
40
30
20
10
0
0.1
1 10 100
LOAD CURRENT (mA)
1000
MAX1796
EFFICIENCY vs. LOAD CURRENT (+3.3V)
100 VBATT = +2.4V
90
80
70 VBATT = +1.2V
60
50
40
30
20
10
0
0.1
1 10 100
LOAD CURRENT (mA)
1000
NO-LOAD BATTERY CURRENT
vs. INPUT BATT VOLTAGE
300
250
200
150
100 VOUT = +5V
50
VOUT = +3.3V
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
BATT VOLTAGE (V)
MAX1797
EFFICIENCY vs. LOAD CURRENT (+5V)
100
90 VBATT = +3.6V
80
70
60 VBATT = +2.4V
50 VBATT = +1.2V
40
30
20
10
0
0.1
1 10 100
LOAD CURRENT (mA)
1000
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.1
STARTUP VOLTAGE
vs. LOAD CURRENT
VOUT = +3.3V
1 10 100
LOAD CURRENT (mA)
1000
MAX1797
EFFICIENCY vs. LOAD CURRENT (+3.3V)
100
90 VBATT = +2.4V
80
70
60
50 VBATT = +1.2V
40
30
20
10
0
0.1
1 10 100
LOAD CURRENT (mA)
1000
SHUTDOWN THRESHOLD
vs. INPUT BATT VOLTAGE
3.0
2.5
2.0
1.5
1.0
0.5
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
BATT VOLTAGE (V)
_______________________________________________________________________________________ 5