19-1666; Rev 1; 10/03
30V Internal Switch LCD Bias Supply
General Description
The MAX1605 boost converter contains a 0.5A internal
switch in a tiny 6-pin SOT23 package. The IC operates
from a +2.4V to +5.5V supply voltage, but can boost
battery voltages as low as 0.8V up to 30V at the output.
The MAX1605 uses a unique control scheme providing
the highest efficiency over a wide range of load condi-
tions. An internal 0.5A MOSFET reduces external com-
ponent count, and a high switching frequency (up to
500kHz) allows for tiny surface-mount components. The
current limit can be set to 500mA, 250mA, or 125mA,
allowing the user to reduce the output ripple and com-
ponent size in low-current applications.
Additional features include a low quiescent supply cur-
rent and a shutdown mode to save power. The
MAX1605 is ideal for small LCD panels with low current
requirements, but can also be used in other applica-
tions. A MAX1605EVKIT evaluation kit (EV kit) is avail-
able to help speed up design time.
Applications
LCD Bias Generators
Cellular/Cordless Phones
Palmtop Computers
Personal Digital Assistants (PDAs)
Organizers
Handy Terminals
Features
o Adjustable Output Voltage up to 30V
o 20mA at 20V from a Single Li+ Battery
o 88% Efficiency
o Up to 500kHz Switching Frequency
o Selectable Inductor Current Limit
(125mA, 250mA, or 500mA)
o 18A Operating Supply Current
o 0.1A Shutdown Current
o Avaiable in Two Small Packages
6-Pin TDFN
6-Pin SOT23
V
IN
= 0.8V TO V
OUT
V
CC
= 2.4V TO 5.5V
V
OUT
= V
IN
TO 30V
ON
OFF
SHDN
V
CC
LIM
GND
LX
FB
MAX1605
L1
10
H
MAX1605
________________________________________________________________ Maxim Integrated Products
1
Pin Configuration
Typical Operating Circuit
V
CC
LX
GND
1
6
FB
5
LIM
SHDN
MAX1605
SOT23
TOP VIEW
2
3
4
LX
FB
LIM
MAX1605
V
CC
GND
SHDN
1
2
3
6
5
4
TDFN
3mm
3mm
Ordering Information
PART
TEMP
RANGE
PIN-
PACKAGE
SOT
MARK
MAX1605EUT-T -40C to +85C
6 SOT23-6
AAHP
MAX1605ETT-T -40C to +85C
6 TDFN
ABW
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.
MAX1605
30V Internal Switch LCD Bias Supply
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= SHDN = 3.3V, T
A
= 0C to +85C, unless otherwise noted. Typical values are at T
A
= +25C.) (Note 1)
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.
V
CC
, FB, LIM, SHDN to GND....................................-0.3V to +6V
LX to GND ..............................................................-0.3V to +32V
Continuous Power Dissipation (T
A
= +70C)
6-Pin SOT23 (derate 8.7mW/C above +70C) ...........696mW
6-Pin TDFN (derate 24.4mW/C above +70C) .........1951mW
Operating Temperature Range ...........................-40C to +85C
Junction Temperature ......................................................+150C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10s) .................................+300C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
V
CC
(Note 2)
2.4
5.5
V
Inductor Input Voltage Range
V
IN
(Note 2)
0.8
V
OUT
V
V
CC
Undervoltage Lockout
V
UVLO
V
CC
falling, 50mV typical hysteresis
2.0
2.2
2.37
V
Quiescent Supply Current
I
CC
V
FB
= 1.3V
18
35
A
Shutdown Supply Current
SHDN = GND
0.1
1
A
V
CC
Line Regulation
V
LNR
V
OUT
= 18V, I
LOAD
= 1mA, V
IN
= 5V,
V
CC
= V
LIM
= 2.4V to 5.5V
0.1
%/V
V
IN
Line Regulation
V
LNR
V
OUT
= 18V, I
LOAD
= 1mA,
V
CC
= V
LIM
= 5V, V
IN
= 2.4V to 12V
0.15
%/V
Load Regulation
V
LDR
V
OUT
= 18V, V
CC
= V
IN
= V
LIM
= 5V,
I
LOAD
= 0mA to 20mA
0.1
%/mA
Efficiency
L1 = 100H, V
IN
= 3.6V, I
LOAD
= 10mA
88
%
Feedback Set Point
V
FB
1.225
1.25
1.275
V
Feedback Input Bias Current
I
FB
V
FB
= 1.3V
5
100
nA
LX
LX Voltage Range
V
LX
30.5
V
LIM = V
CC
0.40
0.50
0.56
LIM = floating
0.20
0.25
0.285
LX Switch Current Limit
I
LX(MAX)
LIM = GND
0.10
0.125
0.15
A
V
CC
= 5V, I
LX
= 100mA
0.8
LX On-Resistance
R
LX
V
CC
= 3.3V, I
LX
= 100mA
1
2
LX Leakage Current
V
LX
= 30.5V
2
A
Maximum LX On-Time
t
ON
10
13
16
s
V
FB
> 1.1V
0.8
1.0
1.2
Minimum LX Off-Time
t
OFF
V
FB
< 0.8V (soft-start)
3.9
5.0
6.0
s
MAX1605
30V Internal Switch LCD Bias Supply
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS
(V
CC
= SHDN = 3.3V, T
A
= -40C to +85C, unless otherwise noted.) (Note 1)
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= SHDN = 3.3V, T
A
= 0C to +85C, unless otherwise noted. Typical values are at T
A
= +25C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CONTROL INPUTS
V
IH
2.4V
V
CC
5.5V
0.8
V
CC
SHDN Input Threshold
V
IL
2.4V
V
CC
5.5V
0.2
V
CC
V
SHDN Input Bias Current
I
SHDN
V
CC
= 5.5V, V
SHDN
= 0 to 5.5V
-1
1
A
LIM Input Low Level
2.4V
V
CC
5.5V
0.4
V
LIM Input Float Level
2.4V
V
CC
5.5V,
I
LIM
= 0.5A
( V
C C
/ 2) -
0.2V
( V
C C
/ 2)
+ 0.2V
V
LIM Input High Level
2.4V
V
CC
5.5V
V
CC
- 0.4V
V
SHDN = V
CC
, LIM = GND or V
CC
-2
2
LIM Input Bias Current
I
LIM
SHDN = GND
0.1
1
A
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Supply Voltage
V
CC
(Note 2)
2.4
5.5
V
Inductor Input Voltage Range
V
IN
(Note 2)
0.8
V
OUT
V
V
CC
Undervoltage Lockout
V
UVLO
V
CC
falling, 50mV typical hysteresis
2.0
2.37
V
Quiescent Supply Current
I
CC
V
FB
= 1.3V
35
A
Shutdown Supply Current
SHDN = GND
1
A
Feedback Set Point
V
FB
1.215
1.285
V
Feedback Input Bias Current
I
FB
V
FB
= 1.3V
100
nA
LX
LX Voltage Range
V
LX
30.5
V
LIM = V
CC
0.35
0.58
LIM = floating
0.18
0.30
LX Switch Current Limit
I
LX(MAX)
LIM = GND
0.08
0.17
A
LX On-Resistance
R
LX
V
CC
= 3.3V, I
LX
= 100mA
2
LX Leakage Current
V
LX
= 30.5V
2
A
Maximum LX On-Time
t
ON
9
17
s
V
FB
> 1.1V
0.75
1.25
Minimum LX Off-Time
t
OFF
V
FB
< 0.8V
3.8
6.0
s
CONTROL INPUTS
V
IH
2.4V
V
CC
5.5V
0.8
V
CC
SHDN Input Threshold
V
IL
2.4V
V
CC
5.5V
0.2
V
CC
V
SHDN Input Bias Current
I
SHDN
V
CC
= 5.5V, V
SHDN
= 0 to 5.5V
-1
1
A
MAX1605
30V Internal Switch LCD Bias Supply
4
_______________________________________________________________________________________
70
72
76
74
78
80
2.0
3.0
2.5
3.5
4.0
4.5
5.0
5.5
MAX1605 toc04
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
EFFICIENCY vs. SUPPLY VOLTAGE
(L1 = 10
H)
80
V
IN
= 3.6V
I
LIM
= 500mA
I
OUT
= 5mA
I
OUT
= 1mA
I
OUT
= 10mA
30
50
40
70
60
80
90
0
6
3
9
12
EFFICIENCY vs. INPUT VOLTAGE
(L1 = 10
H)
MAX1605 toc05
INPUT VOLTAGE (V)
EFFICIENCY (%)
V
CC
= 3.3V
I
LIM
= 500mA
I
OUT
= 5mA
I
OUT
= 1mA
60
80
0
5
10
15
20
25
EFFICIENCY vs. LOAD CURRENT
(L1 = 10
H)
MAX1605 toc06
LOAD CURRENT (mA)
EFFICIENCY (%)
62
64
66
68
70
72
74
76
78
LIM = GND
(125mA)
LIM = OPEN
(250mA)
LIM = V
CC
(500mA)
17.6
17.8
17.7
18.0
17.9
18.1
18.2
2.0
3.5
4.0
2.5
3.0
4.5
5.0
5.5
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX1605 toc01
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
V
IN
= 3.6V
LIM = V
CC
(500mA)
I
OUT
= 5mA
I
OUT
= 1mA
19.5
20.1
19.9
19.7
20.3
20.5
20.7
20.9
21.1
21.3
21.5
0
3
6
9
12
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1605 toc02
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
V
CC
= 3.3V
LIM = V
CC
(500mA)
I
OUT
= 5mA
I
OUT
= 1mA
17.4
17.7
17.6
17.5
17.8
17.9
18.0
18.1
18.2
18.3
18.4
0
10
5
15
20
25
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1605 toc03
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
LIM = V
CC
(500mA)
LIM = GND
(125mA)
LIM = OPEN
(250mA)
Typical Operating Characteristics
(V
CC
= 3.3V, V
IN
= 3.6V, L1 = 10H, SHDN = LIM = V
CC
, V
OUT(NOM)
= 18V (Figure 3), T
A
= +25C, unless otherwise noted.)
Note 1: All devices are 100% tested at T
A
= +25C. All limits over the temperature range are guaranteed by design.
Note 2: The MAX1605 requires a supply voltage between +2.4V and +5.5V; however, the input voltage used to power the inductor
can vary from +0.8V to V
OUT
.
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= SHDN = 3.3V, T
A
= -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
LIM Input Low Level
2.4V
V
CC
5.5V
0.4
V
LIM Input Float Level
2.4V
V
CC
5.5V,
I
LIM
= 0.5A
(V
CC
/ 2)
- 0.25V
(V
CC
/ 2)
+ 0.25V
V
LIM Input High Level
2.4V
V
CC
5.5V
V
CC
- 0.4V
V
SHDN = V
CC
, LIM = GND or V
CC
-2
2
LIM Input Bias Current
I
LIM
SHDN = GND
1
A
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, V
IN
= 3.6V, L1 = 10H, SHDN = LIM = V
CC
, V
OUT(NOM)
= 18V (Figure 3), T
A
= +25C, unless otherwise noted.)
74
76
78
80
82
84
86
88
90
0
5
10
15
20
25
EFFICIENCY vs. LOAD CURRENT
(L1 = 47
H)
MAX1605 toc07
LOAD CURRENT (mA)
EFFICIENCY (%)
LIM = GND
(125mA)
LIM = OPEN
(250mA)
LIM = V
CC
(500mA)
100
200
300
500
400
600
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
CURRENT LIMIT vs. SUPPLY VOLTAGE
MAX1605 toc09
SUPPLY VOLTAGE (V)
CURRENT LIMIT (mA)
LIM = OPEN
LIM = GND
LIM = V
CC
100
200
300
500
400
600
0
3
6
9
12
CURRENT LIMIT vs. INPUT VOLTAGE
MAX1605 toc10
INPUT VOLTAGE (V)
CURRENT LIMIT (mA)
LIM = OPEN
LIM = V
CC
LIM = GND
0
5
15
10
20
25
0
2
1
3
4
5
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (NO-LOAD)
MAX1605 toc11
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
A)
0
1.0
0.5
2.0
1.5
2.5
3.0
0
10
5
15
20
25
MAX1605 toc12
LOAD CURRENT (mA)
SUPPLY CURRENT (mA)
SUPPLY CURRENT vs. LOAD CURRENT
LIM = GND
(125mA)
LIM = OPEN
(250mA)
LIM = V
CC
(500mA)
17.9V
2V
18.1V
18
4V
6V
A
2V/div
200
s/div
LINE TRANSIENT
MAX1605 toc13
A: V
IN
= V
CC
= 2.4V TO 5.5V
B: V
OUT
= 18V, R
OUT
= 3.6k
B
100mV/div
0
17.9V
500mA
18.1V
18V
0
10mA
I
OUT
10mA/div
40
s/div
LOAD TRANSIENT
MAX1605 toc14
V
OUT
= 18V, I
OUT
= 1mA TO 10mA
V
CC
= 3.3V, V
IN
= 3.6V
V
OUT
100mV/div
I
L1
500mA/div
74
76
78
80
82
84
86
88
90
0
5
10
15
20
25
EFFICIENCY vs. LOAD CURRENT
(L1 = 100
H)
MAX1605 toc08
LOAD CURRENT (mA)
EFFICIENCY (%)
LIM = OPEN
(250mA)
LIM = V
CC
(500mA)
LIM = GND
(125mA)
10V
0
0
20V
500mA
250mA
0
2V
4V
V
SHDN
2V/div
200
s/div
SHUTDOWN WAVEFORM
MAX1605 toc15
V
OUT
= 18V, R
OUT
= 1.8k
V
CC
= 3.3V, V
IN
= 3.6V
I
L1
250mA/div
V
OUT
10V/div
MAX1605
30V Internal Switch LCD Bias Supply
_______________________________________________________________________________________
5
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