19-0186; Rev 2; 7/96
ANUAL
N KIT M
LUATIO ATA SHEET
EVA
WS D
FOLLO
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
____________________________Features
o
1V to 4.5V Input Guarantees Start-Up Under Load
o
Up to 210mA Output
o
Load Fully Disconnected in Shutdown
o
82% Efficiency
o
Output in Regulation with Input Voltage above
Output Voltage
o
Internal 1A Power Switch and Active Rectifier
o
Adjustable Current Limit Allows Low-Cost
Inductors
o
190µA No Load Supply Current
o
20µA Shutdown Supply Current
o
3V/3.3V (MAX778L), 5V (MAX777L), and
Adjustable (MAX779L) Output Voltage
_______________General Description
The MAX777L/MAX778L/MAX779L are pulse-skipping DC-DC
converters that step up from low-voltage inputs (1V guaran-
teed). They require only three external components—an induc-
tor (typically 22µH) and two capacitors. The MAX777L delivers
a 5V output, the MAX778L generates pin-selectable voltages of
3.0V or 3.3V, and the MAX779L output can be adjusted from
2.5V to 6V through an external resistive divider.
The devices include an Active Rectifier
TM
that eliminates the
need for an external catch diode, and permits regulation even
when the input is greater than the output. Also, unlike those in
other step-up converters, the MAX777L/MAX778L/MAX779L’s
Active Rectifier
TM
turns off in the shutdown mode, disconnect-
ing the output from the source. This eliminates the current drain
associated with conventional step-up converters when off or in
shutdown.
High-frequency operation (up to 150kHz) allows the use of
small, surface-mount inductors with values of 10µH or less.
Supply current is 190µA under no load and only 20µA in stand-
by mode; supply voltage can range from 1V to 4.5V (1 to 3
cells). With a 2V input, the devices typically deliver 200mA at
5V, or 300mA at 3V.
For fully specified devices designed for step-up/step-down
applications (where the input can be above or below the out-
put), refer to the MAX877L/MAX878L/MAX879L data sheet.
MAX777L/MAX778L/MAX779L
______________Ordering Information
PART
MAX777LCPA
MAX777LCSA
MAX777LC/D
MAX777LEPA
MAX777LESA
MAX777LMJA
TEMP. RANGE
0°C to +70°C
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
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP**
________________________Applications
Single Battery-Cell (1V), Step-Up Voltage Conversion
Efficient, High-Power Step-Up Regulation from
Low Input Voltages
Pagers
Portable Instruments & Hand-Held Terminals
Notebook and Palmtop Computers
Ordering Information continued at end of data sheet.
* Dice are specified at T
A
= +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
__________Typical Operating Circuit
INPUT
1V TO 4.5V
2
__________________Pin Configuration
TOP VIEW
22µF
IN
ILIM
MAX777L
SHDN
PGND
4
LX
OUT
AGND
3
5
6
22µH
ILIM 1
IN 2
8
N.C. (MAX777L)
*
SHDN
OUT
LX
1
7
ON/OFF
OUTPUT
5V
100µF
AGND 3
PGND 4
MAX777L
MAX778L
MAX779L
7
6
5
DIP/SO
*
SEL FOR MAX778L, FB FOR MAX779L.
Active Rectifier is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
MAX777L/MAX778L/MAX779L
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (IN to PGND).......................................0V to 4.5V
Output Short-Circuit Duration to PGND, AGND (Note 1)....30sec
Voltage Applied to:
LX (switch off) .......................................................-0.3V to 4.5V
(switch on) ....................................30sec short to IN or OUT
OUT,
SHDN
...........................................................-0.3V to +7V
FB ...........................................................-0.3V to (OUT + 0.3V)
AGND to PGND ........................................................-0.3V, +0.3V
Reverse Battery Current....................................................900mA
Continuous Power Dissipation (T
A
= +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:
MAX77_LC_A .......................................................0°C to +70°C
MAX77_LE_A ....................................................-40°C to +85°C
MAX77_LMJA .................................................-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 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
= +2.5V, I
LOAD
= 0mA, L = 22µH, C
OUT
= 100µF,
SHDN
and ILIM connected to IN, AGND connected to PGND, T
A
= T
MIN
to T
MAX
,
typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Minimum Start-Up Voltage
CONDITIONS
I
LOAD
< 10mA, T
A
= +25°C (Note 2)
MAX777LC/
MAX779LC
MAX777LE/
MAX779LE
MAX777LM/
MAX779LM
MAX778LC
SEL = 0V
Output Voltage
MAX778L
(Note 6)
SEL = OPEN
MAX778LE
MAX778LM
MAX778LC
MAX778LE
MAX778LM
Output Voltage Range
(MAX779L)
Efficiency
No-Load Supply Current
Shutdown Supply Current
SHDN
Input Current
(Note 4)
I
LOAD
= 100mA
I
LOAD
= 0mA (switch off)
SHDN
= 0V
MAX77_LC, MAX77_LE
MAX77_LM
I
LOAD
≤
30mA, 1.1V
≤
V
IN
≤
4.5V or
I
LOAD
≤
140mA, 1.8V
≤
V
IN
≤
4.5V
I
LOAD
≤
30mA, 1.2V
≤
V
IN
≤
4.5V or
I
LOAD
≤
130mA, 1.8V
≤
V
IN
≤
4.5V
I
LOAD
≤
25mA, 1.25V
≤
V
IN
≤
4.5V or
I
LOAD
≤
120mA, 1.8V
≤
V
IN
≤
4.5V
I
LOAD
≤
50mA, 1.1V
≤
V
IN
≤
3.3V or
I
LOAD
≤
210mA, 1.8V
≤
V
IN
≤
3.3V
I
LOAD
≤
50mA, 1.2V
≤
V
IN
≤
3.3V or
I
LOAD
≤
200mA, 1.8V
≤
V
IN
≤
3.3V
I
LOAD
≤
50mA, 1.25V
≤
V
IN
≤
3.3V or
I
LOAD
≤
180mA, 1.8V
≤
V
IN
≤
3.3V
I
LOAD
≤
50mA, 1.1V
≤
V
IN
≤
3V or
I
LOAD
≤
210mA, 1.8V
≤
V
IN
≤
3V
I
LOAD
≤
50mA, 1.2V
≤
V
IN
≤
3V or
I
LOAD
≤
200mA, 1.8V
≤
V
IN
≤
3V
I
LOAD
≤
40mA, 1.25V
≤
V
IN
≤
3V or
I
LOAD
≤
180mA, 1.8V
≤
V
IN
≤
3V
MIN
4.5
TYP
MAX UNITS
1
V
V
Maximum Operating Voltage (Notes 2, 3)
Output Voltage
MAX777L/MAX779L
(set to 5V)
(Note 6)
4.80
5.00
5.20
V
3.17
3.30
3.43
V
2.88
3.00
3.12
2.5
82
190
20
20
15
12
6.0
V
%
310
30
35
100
40
µA
µA
nA
µA
0V <
SHDN
< V
IN
V
IN
<
SHDN
< 5V
2
_______________________________________________________________________________________
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +2.5V, I
LOAD
= 0mA, L = 22µH, C
OUT
= 100µF,
SHDN
and ILIM connected to IN, AGND connected to PGND, T
A
= T
MIN
to T
MAX
,
typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
SHDN
Threshold
SHDN
Enable Delay
Current Limit
Current-Limit Temperature
Coefficient
I
SW
= 400mA
Switch Saturation Voltage
I
SW
= 600mA
I
SW
= 1000mA
V
IN
= 2.5V
Maximum Switch On Time
V
IN
= 1.8V
V
IN
= 1V
Minimum Switch Off Time
MAX777L, MAX779L
MAX778
I
SW
= 400mA
Rectifier Forward Voltage Drop
Error-Comparator Trip Point
FB Pin Bias Current
Switch Off Leakage Current
Rectifier Off Leakage Current
I
SW
= 600mA
I
SW
= 1000mA
MAX779L, over operating input voltage (Note 5)
MAX779L, V
FB
= 0.3V
197.5
V
IN
= 1V to 4.5V
V
IN
= 2.5V
1.20
150
1.0
-0.3
0.275
0.33
0.50
4.0
5.9
12.6
1.2
2.2
0.21
0.31
0.50
202.5
10
0.1
0.1
207.5
40
mV
nA
µA
µA
V
µs
µs
V
CONDITIONS
MIN
TYP
V
IN
/2 + 0.25
1.6
MAX
UNITS
V
µs
A
%/°C
MAX777L/MAX778L/MAX779L
Note 2:
Output in regulation, V
OUT
= V
OUT
(nominal) ±4%.
Note 3:
At high V
IN
to V
OUT
differentials, the maximum load current is limited by the maximum allowable power dissipation in the
package (see
Absolute Maximum Ratings).
Note 4:
Minimum value is production tested. Maximum value is guaranteed by design and is not production tested.
Note 5:
V
OUT
is set to a target value of +5V by 0.1% external feedback resistors. V
OUT
is measured to be 5V ±2.5% to guarantee the
error comparator trip point.
Note 6:
Start-Up guaranteed under these load conditions.
_______________________________________________________________________________________
3
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
MAX777L/MAX778L/MAX779L
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, T
A
= +25°C, unless otherwise noted).
MAX778L
SHDN THRESHOLD VOLTAGE
vs. INPUT VOLTAGE AND TEMPERATURE
MAX777-8
NO-LOAD SUPPLY CURRENT
vs. VOLTAGE AND TEMPERATURE
MAX777-6
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE AND TEMPERATURE
70
60
50
40
30
20
10
0
1
2
3
T
A
= 0°C
T
A
= -40°C
4
5
6
7
T
A
= +85°C
MAX777-7
300
280
NO-LOAD SUPPLY CURRENT (µA)
260
240
220
200
180
160
140
120
100
1
(SWITCH = OFF)
T
A
= +85°C
80
SHUTDOWN SUPPLY CURRENT (µA)
3.5
SHDN THRESHOLD VOLTAGE (V)
3.0
2.5
2.0
1.5
1.0
T
A
= -55°C
0.5
1
2
3
4
5
6
7
T
A
= +25°C
T
A
= +125°C
T
A
= +25°C
T
A
= -40°C
2
3
T
A
= 0°C
4
5
6
7
SUPPLY VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
MAX777L/MAX779L
EFFICIENCY vs. LOAD CURRENT
MAX777-1
MAX778L
EFFICIENCY vs. LOAD CURRENT
V
OUT
= 3.3V OR 3.0V
80
EFFICIENCY (%)
70
60
50
40
30
0.1
MAX777-2
90
V
OUT
= 5V
80
EFFICIENCY (%)
70
60
50
40
30
0.1
V
IN
= 4V
V
IN
= 2.5V
V
IN
= 1.8V
V
IN
= 1.5V
V
IN
= 1.1V
1
10
100
90
V
IN
= 2.5V
V
IN
= 1.8V
V
IN
= 1.5V
V
IN
= 1.1V
1
10
100
1000
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAX777L/MAX779L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX777-4
MAX778L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
V
OUT
= 3.3V
300
OUTPUT CURRENT (mA)
250
200
150
100
50
0
0.5
MAX777-5
300
V
OUT
= 5V
250
OUTPUT CURRENT (mA)
200
150
100
50
0
0.5
350
1.0
1.5
2.0
2.5
1.0
1.5
2.0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
LINE-TRANSIENT RESPONSE
MAX777L/MAX778L/MAX779L
A
A
B
B
2ms/div
A: I
OUT
, 200mA/div, 0mA to 200mA
B: V
OUT
, 50mV/div, AC COUPLED
MAX778L, V
OUT
= 3.3V, V
IN
= 2.5V
2ms/div
A:
B:
V
IN
, 1V/div, 1.8V to 3.3V
V
OUT
, 100mV/div, AC-COUPLED, I
OUT
= 240mA
MAX778L, V
OUT
= 3.3V
SWITCHING WAVEFORMS,
CONTINUOUS CONDUCTION
SWITCHING WAVEFORMS,
DISCONTINUOUS CONDUCTION
A
A
B
0mA
C
5µs/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, V
IN
= 1.5V, I
OUT
= 100mA
B
C
2µs/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, V
IN
= 3V, I
OUT
= 70mA
_______________________________________________________________________________________
5
