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.
♦
Adjustable Output Voltage up to 30V
♦
20mA at 20V from a Single Li+ Battery
♦
88% Efficiency
♦
Up to 500kHz Switching Frequency
♦
Selectable Inductor Current Limit
(125mA, 250mA, or 500mA)
♦
18µA Operating Supply Current
♦
0.1µA Shutdown Current
♦
Available in Two Small Packages
6-Pin TDFN
6-Pin SOT23
Features
MAX1605
Applications
LCD Bias Generators
Cellular/Cordless Phones
Palmtop Computers
Personal Digital Assistants (PDAs)
Organizers
Handy Terminals
PART
MAX1605EUT-T
MAX1605ETT-T
Ordering Information
TEMP
RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
6 SOT23-6
6 TDFN
SOT
MARK
AAHP
ABW
Typical Operating Circuit
V
IN
= 0.8V TO V
OUT
L1
10µH
Pin Configuration
TOP VIEW
SHDN
1
6
FB
SHDN
V
CC
1
2
3
6
5
4
FB
LIM
V
CC
= 2.4V TO 5.5V
V
OUT
= V
IN
TO 30V
V
CC
MAX1605
GND
3
4
LX
LX
V
CC
2
MAX1605
5
LIM
MAX1605
GND
LX
LIM
ON
OFF
SHDN
FB
SOT23
GND
TDFN
3mm
✕
3mm
________________________________________________________________
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.
30V Internal Switch LCD Bias Supply
MAX1605
ABSOLUTE MAXIMUM RATINGS
V
CC
, FB, LIM,
SHDN
to GND....................................-0.3V to +6V
LX to GND ..............................................................-0.3V to +32V
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C) ...........696mW
6-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW
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
(V
CC
=
SHDN
= 3.3V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage
Inductor Input Voltage Range
V
CC
Undervoltage Lockout
Quiescent Supply Current
Shutdown Supply Current
V
CC
Line Regulation
V
IN
Line Regulation
Load Regulation
Efficiency
Feedback Set Point
Feedback Input Bias Current
LX
LX Voltage Range
LX Switch Current Limit
V
LX
LIM = V
CC
I
LX(MAX)
LIM = floating
LIM = GND
LX On-Resistance
LX Leakage Current
Maximum LX On-Time
Minimum LX Off-Time
t
ON
t
OFF
V
FB
> 1.1V
V
FB
< 0.8V (soft-start)
R
LX
V
CC
= 5V, I
LX
= 100mA
V
CC
= 3.3V, I
LX
= 100mA
V
LX
= 30.5V
10
0.8
3.9
13
1.0
5.0
0.40
0.20
0.10
0.50
0.25
0.125
0.8
1
2
2
16
1.2
6.0
30.5
0.56
0.285
0.15
Ω
µA
µs
µs
A
V
V
FB
I
FB
V
FB
= 1.3V
∆V
LNR
∆V
LNR
∆V
LDR
SYMBOL
V
CC
V
IN
V
UVLO
I
CC
(Note 2)
(Note 2)
V
CC
falling, 50mV typical hysteresis
V
FB
= 1.3V
SHDN
= GND
V
OUT
= 18V, I
LOAD
= 1mA, V
IN
= 5V,
V
CC
= V
LIM
= 2.4V to 5.5V
V
OUT
= 18V, I
LOAD
= 1mA,
V
CC
= V
LIM
= 5V, V
IN
= 2.4V to 12V
V
OUT
= 18V, V
CC
= V
IN
= V
LIM
= 5V,
I
LOAD
= 0mA to 20mA
L1 = 100µH, V
IN
= 3.6V, I
LOAD
= 10mA
1.225
CONDITIONS
MIN
2.4
0.8
2.0
2.2
18
0.1
0.1
0.15
0.1
88
1.25
5
1.275
100
TYP
MAX
5.5
V
OUT
2.37
35
1
UNITS
V
V
V
µA
µA
%/V
%/V
%/mA
%
V
nA
2
_______________________________________________________________________________________
30V Internal Switch LCD Bias Supply
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
=
SHDN
= 3.3V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
CONTROL INPUTS
V
IH
SHDN
Input Threshold
V
IL
SHDN
Input Bias Current
LIM Input Low Level
LIM Input Float Level
LIM Input High Level
LIM Input Bias Current
I
LIM
I
SHDN
2.4V
≤
V
CC
≤
5.5V
V
CC
= 5.5V, V
SHDN
= 0 to 5.5V
2.4V
≤
V
CC
≤
5.5V
2.4V
≤
V
CC
≤
5.5V,
I
LIM
= ±0.5µA
2.4V
≤
V
CC
≤
5.5V
SHDN
= V
CC
, LIM = GND or V
CC
SHDN
= GND
(V
CC
/ 2) -
0.2V
V
CC
- 0.4V
-2
0.1
2
1
-1
2.4V
≤
V
CC
≤
5.5V
0.8
×
V
CC
0.2
×
V
CC
1
0.4
(V
CC
/ 2)
+ 0.2V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1605
V
µA
V
V
V
µA
ELECTRICAL CHARACTERISTICS
(V
CC
=
SHDN
= 3.3V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
Inductor Input Voltage Range
V
CC
Undervoltage Lockout
Quiescent Supply Current
Shutdown Supply Current
Feedback Set Point
Feedback Input Bias Current
LX
LX Voltage Range
LX Switch Current Limit
LX On-Resistance
LX Leakage Current
Maximum LX On-Time
Minimum LX Off-Time
CONTROL INPUTS
V
IH
SHDN
Input Threshold
V
IL
SHDN
Input Bias Current
I
SHDN
2.4V
≤
V
CC
≤
5.5V
V
CC
= 5.5V, V
SHDN
= 0 to 5.5V
-1
2.4V
≤
V
CC
≤
5.5V
0.8
×
V
CC
0.2
×
V
CC
1
t
ON
t
OFF
V
FB
> 1.1V
V
FB
< 0.8V
V
LX
LIM = V
CC
I
LX(MAX)
R
LX
LIM = floating
LIM = GND
V
CC
= 3.3V, I
LX
= 100mA
V
LX
= 30.5V
9
0.75
3.8
0.35
0.18
0.08
30.5
0.58
0.30
0.17
2
2
17
1.25
6.0
Ω
µA
µs
µs
A
V
V
FB
I
FB
V
FB
= 1.3V
SYMBOL
V
CC
V
IN
V
UVLO
I
CC
(Note 2)
(Note 2)
V
CC
falling, 50mV typical hysteresis
V
FB
= 1.3V
SHDN
= GND
1.215
CONDITIONS
MIN
2.4
0.8
2.0
MAX
5.5
V
OUT
2.37
35
1
1.285
100
UNITS
V
V
V
µA
µA
V
nA
V
µA
_______________________________________________________________________________________
3
30V Internal Switch LCD Bias Supply
MAX1605
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
=
SHDN
= 3.3V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
LIM Input Low Level
LIM Input Float Level
LIM Input High Level
LIM Input Bias Current
I
LIM
SYMBOL
CONDITIONS
2.4V
≤
V
CC
≤
5.5V
2.4V
≤
V
CC
≤
5.5V,
I
LIM
= ±0.5µA
2.4V
≤
V
CC
≤
5.5V
SHDN
= V
CC
, LIM = GND or V
CC
SHDN
= GND
(V
CC
/ 2)
- 0.25V
V
CC
- 0.4V
-2
MIN
MAX
0.4
(V
CC
/ 2)
+ 0.25V
UNITS
V
V
V
2
1
µA
Note 1:
All devices are 100% tested at T
A
= +25°C. 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
.
Typical Operating Characteristics
(V
CC
= 3.3V, V
IN
= 3.6V, L1 = 10µH,
SHDN
= LIM = V
CC
, V
OUT(NOM)
= 18V (Figure 3), T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1605 toc02
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
V
IN
= 3.6V
LIM = V
CC
(500mA)
I
OUT
= 5mA
MAX1605 toc01
OUTPUT VOLTAGE vs. INPUT VOLTAGE
21.5
21.3
21.1
OUTPUT VOLTAGE (V)
20.9
20.7
20.5
20.3
20.1
19.9
19.7
V
CC
= 3.3V
LIM = V
CC
(500mA)
0
3
6
INPUT VOLTAGE (V)
9
12
I
OUT
= 1mA
I
OUT
= 5mA
18.4
18.3
18.2
OUTPUT VOLTAGE (V)
18.1
18.0
17.9
17.8
17.7
17.6
17.5
17.4
0
5
LIM = GND
(125mA)
18.1
OUTPUT VOLTAGE (V)
18.0
17.9
17.8
17.7
17.6
2.0
LIM = V
CC
(500mA)
I
OUT
= 1mA
LIM = OPEN
(250mA)
19.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
10
15
20
25
LOAD CURRENT (mA)
EFFICIENCY vs. SUPPLY VOLTAGE
(L1 = 10µH)
MAX1605 toc04
EFFICIENCY vs. INPUT VOLTAGE
(L1 = 10µH)
MAX1605 toc05
EFFICIENCY vs. LOAD CURRENT
(L1 = 10µH)
78
76
EFFICIENCY (%)
74
72
70
68
66
LIM = OPEN
(250mA)
LIM = GND
(125mA)
LIM = V
CC
(500mA)
MAX1605 toc06
80
I
OUT
= 5mA
I
OUT
= 10mA
90
I
OUT
= 5mA
80
EFFICIENCY (%)
70
60
50
40
30
V
CC
= 3.3V
I
LIM
= 500mA
0
3
6
INPUT VOLTAGE (V)
9
I
OUT
= 1mA
80
78
EFFICIENCY (%)
76
74
I
OUT
= 1mA
80
V
IN
= 3.6V
I
LIM
= 500mA
72
64
62
60
12
0
5
10
15
20
25
LOAD CURRENT (mA)
70
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
MAX1605 toc03
18.2
30V Internal Switch LCD Bias Supply
MAX1605
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, V
IN
= 3.6V, L1 = 10µH,
SHDN
= LIM = V
CC
, V
OUT(NOM)
= 18V (Figure 3), T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(L1 = 47µH)
MAX1605 toc07
EFFICIENCY vs. LOAD CURRENT
(L1 = 100µH)
MAX1605 toc08
CURRENT LIMIT vs. SUPPLY VOLTAGE
LIM = V
CC
500
CURRENT LIMIT (mA)
MAX1605 toc09
90
88
86
EFFICIENCY (%)
LIM = OPEN
(250mA)
LIM = GND
(125mA)
90
88
86
EFFICIENCY (%)
84
82
80
78
76
74
0
5
10
15
LIM = V
CC
(500mA)
LIM = GND
(125mA)
LIM = OPEN
(250mA)
600
84
82
80
78
76
74
0
5
400
300
LIM = OPEN
LIM = V
CC
(500mA)
200
LIM = GND
100
10
15
20
25
20
25
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
LOAD CURRENT (mA)
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
CURRENT LIMIT vs. INPUT VOLTAGE
MAX1605 toc10
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (NO-LOAD)
MAX1605 toc11
SUPPLY CURRENT vs. LOAD CURRENT
LIM = GND
(125mA)
LIM = OPEN
(250mA)
MAX1605 toc12
600
LIM = V
CC
25
3.0
2.5
SUPPLY CURRENT (mA)
2.0
1.5
1.0
0.5
0
500
CURRENT LIMIT (mA)
20
SUPPLY CURRENT (µA)
400
LIM = OPEN
300
15
10
200
LIM = GND
5
LIM = V
CC
(500mA)
100
0
3
6
INPUT VOLTAGE (V)
9
12
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
0
5
10
15
20
25
LOAD CURRENT (mA)
LINE TRANSIENT
MAX1605 toc13
LOAD TRANSIENT
MAX1605 toc14
SHUTDOWN WAVEFORM
MAX1605 toc15
4V
I
OUT
10mA/div
10mA
A
2V/div
0
18.1V
18V
B
100mV/div
2V
0
I
L1
250mA/div
200µs/div
V
OUT
= 18V, R
OUT
= 1.8kΩ
V
CC
= 3.3V, V
IN
= 3.6V
V
OUT
10V/div
500mA
250mA
0
I
L1
500mA/div
20V
10V
0
V
SHDN
2V/div
6V
4V
2V
18.1V
18
17.9V
17.9V
500mA
0
200µs/div
A: V
IN
= V
CC
= 2.4V TO 5.5V
B: V
OUT
= 18V, R
OUT
= 3.6kΩ
40µs/div
V
OUT
= 18V, I
OUT
= 1mA TO 10mA
V
CC
= 3.3V, V
IN
= 3.6V
_______________________________________________________________________________________
V
OUT
100mV/div
5
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