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 28V at the output.
The MAX1605 uses a unique control scheme providing
the highest efficiency over a wide range of load conditions. An internal 0.5A MOSFET reduces external component 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 component size in low-current applications.
Additional features include a low quiescent supply current 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 applications. A MAX1605EVKIT evaluation kit (EV kit) is available to help speed up design time.
________________________Applications
LCD Bias Generators
Cellular or Cordless Phones
Palmtop Computers
Personal Digital Assistants (PDAs)
Organizers
Handy Terminals
Features
♦ Adjustable Output Voltage up to 28V
♦ 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
♦ Small 6-Pin SOT23 Package
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
V
IN
= 0.8V TO V
OUT
V
CC
= 2.4V TO 5.5V
V
OUT
= V
IN
TO 28V
ON
OFF
SHDN
V
CC
LIM
GND
LX
FB
MAX1605
L1
10µH
Typical Operating Circuit
19-1666; Rev 0; 7/00
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Ordering Information
PART
MAX1605EUT-T -40°C to +85°C
TEMP.
RANGE
PINPACKAGE
6 SOT23-6 AAHP
SOT
MARK
TOP VIEW
SHDN
V
CC
16FB
MAX1605
2
34
SOT23-6
5 LIM
LXGND
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= SHDN = 3.3V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (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.
VCC, FB, LIM, SHDN to GND....................................-0.3V to +6V
LX to GND ..............................................................-0.3V to +30V
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C) ...........696mW
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
)
Supply Voltage V
Inductor Input Voltage Range V
VCC Undervoltage Lockout V
Quiescent Supply Current I
Shutdown Supply Current SHDN = GND 0.1 1 µA
VCC Line Regulation ∆V
VIN Line Regulation ∆V
Load Regulation ∆V
Efficiency L1 = 100µH, VIN = 3.6V, I
Feedback Set Point V
Feedback Input Bias Current I
LX
LX Voltage Range V
LX On-Resistance R
LX Leakage Current VLX = 28V 2 µA
Maximum LX On-Time t
Minimum LX Off-Time t
CONTROL INPUTS
SHDN Input Threshold
SHDN Input Bias Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
UVLO
CC
LNR
LNR
LDR
FB
FB
LX
LX(MAX
(Note 2) 2.4 5.5 V
(Note 2) 0.8 V
IN
VCC falling, 50mV typical hysteresis 2.0 2.2 2.37 V
VFB = 1.3V 18 35 µA
V
= 18V, I
OUT
= V
V
CC
LIM
V
= 18V, I
OUT
= V
V
CC
LIM
V
= 18V, VCC = VIN = V
OUT
= 0mA to 20mA
I
LOAD
= 1mA, VIN = 5V,
LOAD
= 2.4V to 5.5V
= 1mA,
LOAD
= 5V, VIN = 2.4V to 12V
= 5V,
LIM
= 10mA 88 %
LOAD
0.1 %/V
0.15 %/V
0.1 %/mA
1.225 1.25 1.275 V
VFB = 1.3V 5 100 nA
LIM = V
CC
0.40 0.50 0.56
LIM = floating 0.20 0.25 0.285LX Switch Current Limit I
OUT
28 V
LIM = GND 0.10 0.125 0.15
LX
ON
OFF
V
V
SHDN
VCC = 5V, ILX = 100mA 0.8
VCC = 3.3V, ILX = 100mA 1 2
10 13 16 µs
VFB > 1.1V 0.8 1.0 1.2
VFB < 0.8V (soft-start) 3.9 5.0 6.0
IH
IL
2.4V ≤ VCC ≤ 5.5V
2.4V ≤ VCC ≤ 5.5V
VCC = 5.5V, V
SHDN
= 0 to 5.5V -1 1 µA
0.8 ×
V
CC
0.2 ×
V
CC
V
A
Ω
µs
V
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS
(VCC= SHDN = 3.3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)
ELECTRICAL CHARACTERISTICS (continued)
(VCC= SHDN = 3.3V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
)
LIM Input Low Level 2.4V ≤ VCC ≤ 5.5V 0.4 V
LIM Input Float Level
LIM Input High Level 2.4V ≤ VCC ≤ 5.5V
LIM Input Bias Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LIM
2.4V ≤ V
I
LIM
SHDN = VCC, LIM = GND or V
SHDN = GND 0.1 1
≤ 5.5V,
CC
= ±0.5µA
CC
/ 2) -
( V
C C
0.2V
V
CC
- 0.4V
-2 2
( V
C C
+ 0.2V
/ 2)
Supply Voltage V
Inductor Input Voltage Range V
VCC Undervoltage Lockout V
Quiescent Supply Current I
Shutdown Supply Current SHDN = GND 1 µA
Feedback Set Point V
Feedback Input Bias Current I
LX
LX Voltage Range V
LX On-Resistance R
LX Leakage Current VLX = 28V 2 µA
Maximum LX On-Time t
Minimum LX Off-Time t
CONTROL INPUTS
SHDN Input Threshold
SHDN Input Bias Current I
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
CC
UVLO
CC
FB
FB
LX(MAX
ON
OFF
V
V
SHDN
(Note 2) 2.4 5.5 V
(Note 2) 0.8 V
IN
VCC falling, 50mV typical hysteresis 2.0 2.37 V
VFB = 1.3V 35 µA
1.215 1.285 V
VFB = 1.3V 100 nA
LX
LIM = V
CC
LIM = floating 0.18 0.30LX Switch Current Limit I
LIM = GND 0.08 0.17
VCC = 3.3V, ILX = 100mA 2 Ω
LX
VFB > 1.1V 0.75 1.25
VFB < 0.8V 3.8 6.0
2.4V ≤ VCC ≤ 5.5V
IH
2.4V ≤ VCC ≤ 5.5V
IL
VCC = 5.5V, V
= 0 to 5.5V -1 1 µA
SHDN
0.35 0.58
917µs
0.8 ×
V
CC
OUT
28 V
0.2 ×
V
CC
V
V
µA
V
A
µs
V
70
72
76
74
78
80
2.0 3.02.5 3.5 4.0 4.5 5.0 5.5
MAX1605 toc04
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
EFFICIENCY vs.
SUPPLY VOLTAGE
(L1 = 10µH)
80
VIN = 3.6V
I
LIM
= 500mA
I
OUT
= 5mA
I
OUT
= 1mA
I
OUT
= 10mA
30
50
40
70
60
80
90
063912
EFFICIENCY vs.
INPUT VOLTAGE (L1 = 10µH)
MAX1605 toc05
INPUT VOLTAGE (V)
EFFICIENCY (%)
VCC = 3.3V
I
LIM
= 500mA
I
OUT
= 5mA
I
OUT
= 1mA
74
76
78
80
82
84
86
88
90
0 5 10 15 20 25
EFFICIENCY vs. LOAD CURRENT
(L1 = 10µH)
MAX1605 toc06
LOAD CURRENT (mA)
EFFICIENCY (%)
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 4.02.5 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
036912
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
0105 152025
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
(VCC= 3.3V, VIN= 3.6V, L1 = 10µH, SHDN = LIM = VCC, V
OUT(NOM)
= 18V (Figure 3), TA= +25°C, unless otherwise noted.)
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
.
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VCC= SHDN = 3.3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)
LIM Input Low Level 2.4V ≤ VCC ≤ 5.5V 0.4 V
LIM Input Float Level
LIM Input High Level 2.4V ≤ VCC ≤ 5.5V
LIM Input Bias Current I
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
2.4V ≤ V
= ±0.5µA
I
LIM
CC
≤ 5.5V,
(V
CC
- 0.25V
V
CC
/ 2)
(VCC / 2)
+ 0.25V
- 0.4V
LIM
SHDN = VCC, LIM = GND or V
CC
SHDN = GND 1
-2 2
V
V
µA
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(VCC= 3.3V, VIN= 3.6V, L1 = 10µH, SHDN = LIM = VCC, V
OUT(NOM)
= 18V (Figure 3), TA= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(L1 = 47µH)
90
88
86
84
82
80
EFFICIENCY (%)
78
76
74
0 5 10 15 20 25
LIM = OPEN
(250mA)
LIM = GND
(125mA)
LOAD CURRENT (mA)
CURRENT LIMIT vs. INPUT VOLTAGE
600
LIM = V
500
400
300
CURRENT LIMIT (mA)
200
CC
LIM = OPEN
LIM = GND
LIM = V
(500mA)
MAX1605 toc07
EFFICIENCY (%)
CC
MAX1605 toc10
SUPPLY CURRENT (µA)
EFFICIENCY vs. LOAD CURRENT
90
88
86
84
82
80
78
76
74
0 5 10 15 20 25
SUPPLY VOLTAGE (NO LOAD)
25
20
15
10
5
(L1 = 100µH)
LIM = GND
(125mA)
LOAD CURRENT (mA)
LIM = OPEN
(250mA)
LIM = V
(500mA)
SUPPLY CURRENT vs.
CURRENT LIMIT vs. SUPPLY VOLTAGE
600
LIM = V
LIM = OPEN
CC
LIM = V
(500mA)
MAX1605 toc09
MAX1605 toc12
CC
MAX1605 toc08
500
400
300
CURRENT LIMIT (mA)
CC
200
LIM = GND
100
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
SUPPLY CURRENT vs. LOAD CURRENT
3.0
2.5
MAX1605 toc11
2.0
1.5
1.0
SUPPLY CURRENT (mA)
0.5
LIM = GND
(125mA)
LIM = OPEN
(250mA)
100
036912
INPUT VOLTAGE (V)
18.1V
17.9V
6V
4V
2V
18
A: VIN = V
B: V
OUT
LINE TRANSIENT
= 2.4V TO 5.5V
CC
= 18V, R
OUT
200µs/div
= 3.6kΩ
MAX1605 toc13
A
2V/div
B
0
021 345
SUPPLY VOLTAGE (V)
LOAD TRANSIENT
10mA
0
18.1V
18V
17.9V
500mA
100mV/div
0
40µs/div
V
= 18V, I
OUT
= 3.3V, VIN = 3.6V
V
CC
= 1mA TO 10mA
OUT
MAX1605 toc14
OUT
I
OUT
V
L1
I
10mA/div
0
0105 152025
LOAD CURRENT (mA)
SHUTDOWN WAVEFORM
4V
2V
0
500mA
250mA
100mV/div
0
20V
10V
500mA/div
0
200µs/div
V
= 18V, R
OUT
= 3.3V, VIN = 3.6V
V
CC
OUT
= 1.8kΩ
MAX1605 toc15
SHDN
V
2V/div
IL1250mA/div
OUT
10V/div
V
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
6 _______________________________________________________________________________________
Pin Description
Detailed Description
The MAX1605 compact, step-up DC-DC converter
operates from a +2.4V to +5.5V supply. Consuming
only 18µA of supply current, the device includes an
internal switching MOSFET with 1Ω on-resistance and
selectable current limit (Figure 1). During startup, the
MAX1605 extends the minimum off-time, limiting initial
surge current. The MAX1605 also features a shutdown
mode.
Control Scheme
The MAX1605 features a minimum off-time, current-limited control scheme. The duty cycle is governed by a
pair of one-shots that set a minimum off-time and a
maximum on-time. The switching frequency can be up
Figure 1. Functional Diagram
PIN NAME FUNCTION
1 SHDN
2VCCIC Supply Voltage (+2.4V to +5.5V). Bypass VCC to GND with a 0.1µF or greater capacitor.
3 GND Ground
4LX
5 LIM
6FB
V
= 0.8V TO V
IN
OUT
Active-Low Shutdown Input. A logic low shuts down the device and reduces the supply current
to 0.1µA. Connect SHDN to V
for normal operation.
CC
Inductor Connection. The drain of an internal 28V N-channel MOSFET. LX is high impedance in
shutdown.
Inductor Current Limit Selection. Connect LIM to V
for 500mA, leave LIM floating for 250mA,
CC
or connect LIM to GND for 125mA.
Feedback Input. Connect to a resistive-divider network between the output (V
the output voltage between V
and 28V. The feedback threshold is 1.25V.
IN
L1
10µH
) and FB to set
OUT
V
= VIN TO 28V
LX
OUT
CONTROL
= 2.4V TO 5.5V
V
CC
ON
OFF
V
CC
LIM
SHDN
SHUTDOWN
LOGIC
MAX1605
LOGIC
ERROR
AMPLIFIER
C
OUT
R1
R2
CURRENT
LIMIT
1.25V
C
FF
N
FB
GND
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
_______________________________________________________________________________________ 7
to 500kHz and depends upon the load and input voltage. The peak current limit of the internal N-channel
MOSFET is pin selectable and may be set at 125mA,
250mA, or 500mA (Figure 2).
Setting the Output Voltage (FB)
Adjust the output voltage by connecting a voltagedivider from the output (V
OUT
) to FB (Figure 3). Select
R2 between 10kΩ to 200kΩ. Calculate R1 with the following equation:
R1 = R2 [(V
OUT
/ VFB) – 1]
where VFB= 1.25V and V
OUT
may range from VINto
28V. The input bias current of FB has a maximum value
of 100nA, which allows large-value resistors to be used.
For less than 1% error, the current through R2 should
be greater than 100 times the feedback input bias current (IFB).
Current Limit Select Pin (LIM)
The MAX1605 allows a selectable inductor current limit
of 125mA, 250mA, or 500mA (Figure 2). This allows
flexibility in designing for higher current applications or
for smaller, compact designs. The lower current limit
allows the use of a physically smaller inductor in spacesensitive, low-power applications. Connect LIM to V
CC
for 500mA, leave floating for 250mA, or connect to
GND for 125mA.
Shutdown (
SHDN
)
Pull SHDN low to enter shutdown. During shutdown, the
supply current drops to 0.1µA and LX enters a highimpedance state. However, the output remains connected to the input through the inductor and output
rectifier, holding the output voltage to one diode drop
below VINwhen the MAX1605 is shut down. The capacitance and load at OUT determine the rate at which
V
OUT
decays. SHDN can be pulled as high as 6V,
regardless of the input and output voltages.
Separate/Same Power for L1 and V
CC
Separate voltage sources can supply the inductor (VIN)
and the IC (VCC). This allows operation from low-voltage batteries as well as high-voltage sources (0.8V to
28V) because chip bias is provided by a logic supply
(2.4V to 5.5V) while the output power is sourced directly from the battery to L1. Conversely, VINand VCCcan
also be supplied from one supply if it remains within
VCC’s operating limits (+2.4V to +5.5V).
V
Figure 2. Setting the Peak Inductor Current Limit
Figure 3. Typical Application Circuit
CC
(2.4V TO 5.5V)
V
CC
V
CC
MAX1605 MAX1605 MAX1605
LIM
(2.4V TO 5.5V)
NO CONNECTION
V
LIM
CC
V
CC
(2.4V TO 5.5V)
V
LIM
CC
GND
I
= 500mA I
PEAK
GND
= 250mA I
PEAK
GND
PEAK
= 125mA
L1
V
CC
LIM
SHDN
10µH
MAX1605
GND
V
D1
LX
FB
OUT
R1
2.2MΩ
R2
165k
V
= 0.8V TO V
IN
V
CC
C1
0.1µF
ON
OUT
C
IN
10µF
= 2.4V TO 5.5V
OFF
= 18V
C
10pF
C
OUT
FF
1µF
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
8 _______________________________________________________________________________________
Design Procedure
Inductor Selection
Smaller inductance values typically offer smaller physical size for a given series resistance or saturation current. Circuits using larger inductance values may start
up at lower input voltages and exhibit less ripple, but
also provide reduced output power. This occurs when
the inductance is sufficiently large to prevent the maximum current limit from being reached before the maximum on-time expires. The inductor’s saturation current
rating should be greater than the peak switching current. However, it is generally acceptable to bias the
inductor into saturation by as much as 20%, although
this will slightly reduce efficiency.
Picking the Current Limit
The peak LX current limit (I
LX(MAX
)) required for the
application may be calculated from the following equation:
where t
OFF(MIN)
= 0.8µs, and V
IN(MIN)
is the minimum
voltage used to supply the inductor. The set current
limit must be greater than this calculated value. Select
the appropriate current limit by connecting LIM to VCC,
GND, or leaving it unconnected (see Current Limit
Select Pin and Figure 2).
Diode Selection
The high maximum switching frequency of 500kHz
requires a high-speed rectifier. Schottky diodes, such as
the Motorola MBRS0530 or the Nihon EP05Q03L, are
recommended. To maintain high efficiency, the average
current rating of the Schottky diode should be greater
than the peak switching current. Choose a reverse
breakdown voltage greater than the output voltage.
Output Filter Capacitor
For most applications, use a small ceramic surfacemount output capacitor, 1µF or greater. For small
ceramic capacitors, the output ripple voltage is dominated by the capacitance value. If tantalum or electrolytic capacitors are used, the higher ESR increases
the output ripple voltage. Decreasing the ESR reduces
the output ripple voltage and the peak-to-peak transient
voltage. Surface-mount capacitors are generally preferred because they lack the inductance and resistance of their through-hole equivalents.
Input Bypass Capacitor
Two inputs, VCCand VIN, require bypass capacitors.
Bypass VCCwith a 0.1µF ceramic capacitor as close to
the IC as possible. The input supplies high currents to
the inductor and requires local bulk bypassing close to
the inductor. A 10µF low-ESR surface-mount capacitor
is sufficient for most applications.
PC Board Layout and Grounding
Careful printed circuit layout is important for minimizing
ground bounce and noise. Keep the MAX1605’s
ground pin and the ground leads of the input and output capacitors less than 0.2in (5mm) apart. In addition,
keep all connections to FB and LX as short as possible.
In particular, when using external feedback resistors,
locate them as close to FB as possible. To minimize
output voltage ripple, and to maximize output power
and efficiency, use a ground plane and solder GND
directly to the ground plane. Refer to the
MAX1605EVKIT evaluation kit for a layout example.
Applications Information
Negative Voltage for LCD Bias
The MAX1605 can also generate a negative output by
adding a diode-capacitor charge-pump circuit (D1, D2,
and C3) to the LX pin as shown in Figure 4. Feedback
is still connected to the positive output, which is not
loaded, allowing a very small capacitor value at C4. For
best stability and lowest ripple, the time constant of the
R1-R2 series combination and C4 should be near or
less than that of C2 and the effective load resistance.
Output load regulation of the negative output is somewhat looser than with the standard positive output circuit, and may rise at very light loads due to coupling
through the capacitance of D2. If this is objectionable,
reduce the resistance of R1 and R2, while maintaining
their ratio, to effectively preload the output with a few
hundred microamps. This is why the R1-R2 values
shown in Figure 3 are about 10-times lower than typical
values used for a positive-output design. When loaded,
the negative output voltage will be slightly lower (closer
to ground by approximately a diode forward voltage)
than the inverse of the voltage on C4.
Output Disconnected in Shutdown
When the MAX1605 is shut down, the output remains
connected to the input (Figure 3), so the output voltage
falls to approximately V
IN
- 0.6V (the input voltage
minus a diode drop). For applications that require output isolation during shutdown, add an external PNP
transistor as shown in Figure 4. When the MAX1605 is
active, the voltage set at the transistor’s emitter
exceeds the input voltage, forcing the transistor into the
I
LX MAX
≥
()
VI
×
OUT OUT MAX
()
V
()
IN MIN
VV t
()
+
−
OUT IN MIN OFF MIN
×
() ()
L
×2
saturation region. When shut down, the input voltage
exceeds the emitter voltage so the inactive transistor
provides high-impedance isolation between the input
and output. Efficiency will be slightly degraded due to
the PNP transistor saturation voltage and base current.
Figure 4. Negative Voltage for LCD Bias
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
_______________________________________________________________________________________ 9
Figure 5. Output Disconnected in Shutdown
Chip Information
TRANSISTOR COUNT: 2329
L1
V
CC
LIM
SHDN
10µH
LX
MAX1605
FB
GND
V
=
IN
0.8V TO
V
OUT
V
CC
2.4V TO
5.5V
C5
1µF
=
C6
0.1µF
ON
OFF
R3
C3
1Ω
D3**
R1
240k
0.1µF
*D1, D2 =
D1*
D2*
1000pF
**D3 =
C1
16.5k
C4
0.01µF
R2
CENTRAL SEMICONDUCTOR
CMPD7000 DUAL
CENTRAL SEMICONDUCTOR
CMSD4448 (1N4148)
1µF
C2
V
-19V
NEG
L1
V
V
= 2.4V TO 5.5V
CC
ON
= 0.8V TO V
IN
OFF
OUT
V
LIM
SHDN
CC
10µH
LX
MAX1605
FB
GND
R1
R2
R3 = 180k
= 18.3V
V
SET
+0.3V)
(V
OUT
2N2907A
= 18V
V
OUT
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
10 ______________________________________________________________________________________
Package Information
6LSOT.EPS
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
______________________________________________________________________________________ 11
NOTES
MAX1605
28V Internal Switch LCD Bias Supply
in SOT23
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
NOTES
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