19-1975; Rev 2; 7/03
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
General Description
The MAX1776 high-efficiency step-down converter pro-
vides an adjustable output voltage from 1.25V to V
IN
from
supply voltages as high as 24V. An internal current-limit-
ed 0.4Ω MOSFET delivers load currents up to 600mA.
Operation to 100% duty cycle minimizes dropout volt-
age (240mV at 600mA).
The MAX1776 has a low 15µA quiescent current to
improve light-load efficiency and conserve battery life.
The device draws only 3µA while in shutdown.
High switching frequencies (up to 200kHz) allow the
use of tiny surface-mount inductors and output capaci-
tors. The MAX1776 is available in an 8-pin µMAX pack-
age, which uses half the space of an 8-pin SO. For
increased output drive capability, use the MAX1626/
MAX1627 step-down controllers, which drive an exter-
nal P-channel MOSFET to deliver up to 20W.
o
Fixed 5V or Adjustable Output
o
4.5V to 24V Input Voltage Range
o
Up to 600mA Output Current
o
Internal 0.4Ω P-Channel MOSFET
o
Efficiency Over 95%
o
15µA Quiescent Supply Current
o
3µA Shutdown Current
o
100% Maximum Duty Cycle for Low Dropout
o
Current-Limited Architecture
o
Thermal Shutdown
o
Small 8-µMAX Package
Features
MAX1776
Applications
Notebook Computers
Distributed Power Systems
Keep-Alive Supplies
Hand-Held Devices
PART
MAX1776EUA
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
Typical Operating Circuit
TOP VIEW
SHDN
IN
V
IN
Pin Configuration
ILIM
MAX1776
ILIM2
LX
V
OUT
FB
GND
ILIM
1
2
3
4
MAX1776EUA
8
7
6
5
OUT
SHDN
ILIM2
IN
OUT
LX
µMAX
FB
GND
µMAX
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
MAX1776
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
ILIM, ILIM2 to GND .................................-0.3V to 25V
LX to GND.......................................................-2V to (V
IN
+ 0.3V)
OUT, FB to GND .........................................................-0.3V to 6V
Peak Input Current .................................................................. 2A
Maximum DC Input Current.............................................. 500mA
Continuous Power Dissipation (T
A
= +70°C)
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
(Circuit of Figure 1, V
IN
= +12V,
SHDN
= IN,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Input Voltage Range
Input Supply Current
Input Supply Current in Dropout
Input Shutdown Current
Input Undervoltage Lockout
Threshold
Output Voltage (Preset Mode)
Feedback Set Voltage
(Adjustable Mode)
OUT Bias Current
OUT Pin Maximum Voltage
FB Bias Current
FB Dual Mode™ Threshold Low
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
t
OFF(MIN)
t
ON(MAX)
V
FB
= 1.3V
ILIM = ILIM2 = GND
V
IN
= 6V
LX Switch On-Resistance
R
LX
V
IN
= 4.5V
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
ILIM = ILIM2 = GND
LX Current Limit
I
LX(PEAK)
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
LX Zero-Crossing Threshold
Zero-Crossing Timeout
LX Switch Leakage Current
LX does not rise above the threshold
V
IN
= 24V,
LX = GND
T
A
= +25°C
T
A
= 0°C to +85°C
120
240
480
960
-75
30
1
10
I
FB
V
FB
= 1.3V
-25
50
0.22
8
100
0.42
10
1.6
0.8
0.4
0.4
1.9
1.0
0.5
0.5
150
300
600
1200
V
UVLO
V
OUT
V
FB
V
OUT
= 5.5V
SYMBOL
V
IN
I
IN
I
IN(DROP)
No load
No load
SHDN
= GND
V
IN
rising
V
IN
falling
FB = GND
3.6
3.5
4.80
1.212
1.65
CONDITIONS
MIN
4.5
15
50
3
4.0
3.9
5.00
1.25
3.5
TYP
MAX
24
28
70
7
4.4
4.3
5.20
1.288
6.25
5.5
+25
150
0.62
12
3.2
1.6
0.8
0.8
3.8
1.9
0.95
0.95
180
360
720
1440
+75
mV
µs
µA
mA
Ω
UNITS
V
µA
µA
µA
V
V
V
µA
V
nA
mV
µs
µs
Dual Mode is a trademark of Maxim Integrated Products, Inc.
2
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= +12V,
SHDN
= IN,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Dropout Voltage
Line Regulation
Load Regulation
Digital Input Level
Digital Input Leakage Current
ILIM Input Level
Thermal Shutdown
SYMBOL
CONDITIONS
V
IN
= 8V/24V, 200Ω load
No load/full load
SHDN,
ILIM2
Low
High
2.4
-1
2.2
160
+1
0.05
MIN
TYP
0.2
0.1
0.9
0.8
MAX
UNITS
V
%/V
%
V
µA
V
°C
MAX1776
V
DROPOUT
I
OUT
= 525mA, ILIM = ILIM2 = IN
V
SHDN
, V
ILIM
, V
ILIM2
= 0 or 24V, V
IN
= 24V
Low
High
10°C hysteresis
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= +12V,
SHDN
= IN,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Voltage Range
Input Supply Current
Input Supply Current in Dropout
Input Shutdown Current
Input Undervoltage Lockout
Threshold
Output Voltage (Preset Mode)
Feedback Set Voltage
(Adjustable Mode)
OUT Bias Current
OUT Pin Maximum Voltage
FB Bias Current
FB Dual Mode Threshold Low
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
t
OFF(MIN)
t
ON(MAX)
V
FB
= 1.3V
ILIM = ILIM2 = GND
V
IN
= 6V
LX Switch On-Resistance
R
LX
V
IN
= 4.5V
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
ILIM = ILIM2 = GND
LX Current Limit
I
LX(PEAK)
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
100
200
400
800
I
FB
V
FB
= 1.3V
-25
45
0.22
7.5
V
UVLO
V
OUT
V
FB
V
OUT
= 5.5V
SYMBOL
V
IN
I
IN
I
IN(DROP)
No load
No load
SHDN
= GND
V
IN
rising
V
IN
falling
FB = GND
3.6
3.5
4.75
1.2
1.65
CONDITIONS
MIN
4.5
MAX
24
28
70
7
4.4
4.3
5.25
1.3
6.25
5.5
+25
155
0.64
12.5
3.2
1.6
0.8
0.8
3.8
1.9
0.95
0.95
200
400
800
1600
mA
Ω
UNITS
V
µA
µA
µA
V
V
V
µA
V
nA
mV
µs
µs
_______________________________________________________________________________________
3
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
MAX1776
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= +12V,
SHDN
= IN,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
LX Zero-Crossing Threshold
LX Switch Leakage Current
Digital Input Level
Digital Input Leakage Current
ILIM Input Level
V
IN
= 24V, LX = GND
SHDN,
ILIM2
Low
High
2.4
-1
2.2
1
0.05
SYMBOL
CONDITIONS
MIN
-75
MAX
75
10
0.8
UNITS
mV
µA
V
µA
V
V
SHDN
, V
ILIM
, V
ILIM2
= 0 or 24V, V
IN
= 24V
Low
High
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, components from Table 3, V
IN
= +12V,
SHDN
= IN, T
A
= +25°C.)
LOAD REGULATION,
CIRCUIT 1, V
OUTPUT
= 5V
MAX1776 toc01
LOAD REGULATION,
CIRCUIT 1, V
OUTPUT
= 3.3V
MAX1776 toc02
LOAD REGULATION, CIRCUIT 2
MAX1776 toc03
0.2
0
-0.2
V
OUTPUT
(%)
-0.4
-0.6
-0.8
-1.0
V
IN
= 15V
-1.2
0
100
200
300
400
500
600
V
IN
= 24V
V
IN
= 12V
0.6
0.4
0.2
V
OUTPUT
(%)
V
IN
= 5V
0.2
0
-0.2
V
OUTPUT
(%)
-0.4
-0.6
-0.8
-1.0
-1.2
V
IN
= 12V
V
IN
= 15V
V
IN
= 24V
0
-0.2
-0.4
-0.6
-0.8
-1.0
0
100
200
300
I
LOAD
(mA)
400
500
600
V
IN
= 12V
V
IN
= 24V
V
IN
= 15V
700
0
50
100 150 200 250 300 350 400
I
LOAD
(mA)
I
LOAD
(mA)
LOAD REGULATION, CIRCUIT 5
-0.1
V
OUTPUT
(% FROM V
OUT(NOM)
)
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
1.0
0
0.1
0.2
0.3
I
LOAD
(A)
0.4
0.5
0.6
-3
5
7
V
IN
= 15V
V
IN
= 24V
V
OUTPUT
(%)
1
0
V
IN
= 12V
MAX1776 toc04
V
OUTPUT
vs. V
IN
,
CIRCUIT 5, V
OUTPUT
= 5V
MAX1776 toc05
V
OUTPUT
vs. V
IN
,
CIRCUIT 5, V
OUTPUT
= 3.3V
MAX1776 toc06
0
3
2
I
LOAD
= 1mA
I
LOAD
= 50mA
2.0
1.5
1.0
I
LOAD
= 1mA
0.5
0
-0.5
I
LOAD
= 50mA
-1.0
I
LOAD
= 10mA
I
LOAD
= 500mA
-1
-2
9
11 13 15 17 19 21 23 25
V
IN
(V)
V
OUTPUT
(%)
5
7
9
11 13 15 17 19 21 23 25
V
IN
(V)
4
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1, components from Table 3, V
IN
= +12V,
SHDN
= IN, T
A
= +25°C.)
MAX1776
V
OUTPUT
vs. V
IN
,
CIRCUIT 1, V
OUTPUT
= 5V
MAX1776 toc07
V
OUTPUT
vs. V
IN
,
CIRCUIT 1, V
OUTPUT
= 3.3V
MAX1776 toc08
EFFICIENCY vs. I
LOAD
, CIRCUIT 1,
V
OUT
= 5V
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
V
IN
= 15V
V
IN
= 24V
V
IN
= 6V
V
IN
= 12V
MAX1776 toc09
0.4
I
LOAD
= 10mA
0.2
0
V
OUTPUT
(%)
-0.2
-0.4
-0.6
-0.8
1.0
5
7
9
I
LOAD
= 50mA
I
LOAD
= 500mA
I
LOAD
= 1mA
0.6
0.4
0.2
V
OUTPUT
(%)
0
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
I
LOAD
= 50mA
I
LOAD
= 500mA
I
LOAD
= 10mA
I
LOAD
= 1mA
100
11 13 15 17 19 21 23 25
V
IN
(V)
5
7
9
11 13 15 17 19 21 23 25
V
IN
(V)
0.10
1
10
I
LOAD
(mA)
100
1000
EFFICIENCY vs. I
LOAD
, CIRCUIT 5,
V
OUTPUT
= 3.3V
MAX1776 toc10
EFFICIENCY vs. I
LOAD
, CIRCUIT 1,
V
OUTPUT
= 3.3V
MAX1776 toc11
EFFICIENCY vs. V
IN
, I
LOAD
= 500mA
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
CIRCUIT 1, 3.3V
CIRCUIT 5, 3.3V
CIRCUIT 5, 5V
MAX1776 toc12
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0.10
1
10
I
LOAD
(mA)
100
V
IN
= 15V
V
IN
= 24V
V
IN
= 6V
V
IN
= 12V
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
V
IN
= 24V
V
IN
= 12V
V
IN
= 6V
100
CIRCUIT 1, 5V
1000
0.10
1
10
I
LOAD
(mA)
100
1000
7
8
9
10
11
12
13
14
15
16
V
IN
(V)
SWITCHING FREQUENCY vs.
LOAD CURRENT, CIRCUIT 1
MAX1776 toc13
SWITCHING FREQUENCY vs.
V
IN,
CIRCUIT 1
MAX1776 toc14
V
OUTPUT
ACCURACY vs. TEMPERATURE
MAX1776 toc15
200
180
160
FREQUENCY (kHz)
140
120
100
80
60
40
20
0
0
V
IN
= 12V
V
IN
= 24V
V
IN
= 15V
140
120
FREQUENCY (kHz)
100
80
60
40
20
0
I
LOAD
= 250mA
I
LOAD
= 5mA
I
LOAD
= 50mA
I
LOAD
= 10mA
I
LOAD
= 500mA
I
LOAD
= 375mA
1.5
1.0
V
OUT
ACCURACY (%)
0.5
0
-0.5
-1.0
-1.5
100 200 300 400 500 600 700 800 900
I
LOAD
(mA)
5
10
15
V
IN
(V)
20
25
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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