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MAX1605
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 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/Cordless Phones
Palmtop Computers
Personal Digital Assistants (PDAs)
Organizers
Handy Terminal
Features
●●
●●
●●
●●
●●
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
Ordering Information
PART
TEMP
RANGE
PINPACKAGE
SOT
MARK
MAX1605EUT+T
-40°C to +85°C
6 SOT23-6
AAHP
MAX1605ETT+T
-40°C to +85°C
6 TDFN
ABW
Typical Operating Circuit
L1
10µH
VIN = 0.8V TO VOUT
Pin Configuration
VCC = 2.4V TO 5.5V
TOP VIEW
SHDN 1
6
FB
1
VCC 2
5
LIM
VCC
2
GND 3
4
LX
GND
3
19-1666; Rev 2; 8/18
LX
MAX1605
SHDN
MAX1605
SOT23
VOUT = VIN TO 30V
VCC
MAX1605
TDFN
(3mm x 3mm)
6
FB
5
LIM
4
LX
LIM
FB
ON
OFF
SHDN
GND
MAX1605
30V Internal Switch LCD Bias Supply
Absolute Maximum Ratings
VCC, FB, LIM, SHDN to GND..................................-0.3V to +6V
LX to GND..............................................................-0.3V to +32V
Continuous Power Dissipation (TA = +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
(VCC = SHDN = 3.3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
VCC
(Note 2)
2.4
5.5
V
Inductor Input Voltage Range
VIN
(Note 2)
0.8
VOUT
V
VCC falling, 50mV typical hysteresis
2.0
2.2
2.37
V
VFB = 1.3V
18
35
µA
SHDN = GND
0.1
1
µA
VCC Undervoltage Lockout
VUVLO
Quiescent Supply Current
ICC
Shutdown Supply Current
VCC Line Regulation
ΔVLNR
VOUT = 18V, ILOAD = 1mA, VIN = 5V,
VCC = VLIM = 2.4V to 5.5V
0.1
%/V
VIN Line Regulation
ΔVLNR
VOUT = 18V, ILOAD = 1mA,
VCC = VLIM = 5V, VIN = 2.4V to 12V
0.15
%/V
Load Regulation
ΔVLDR
VOUT = 18V, VCC = VIN = VLIM = 5V,
ILOAD = 0mA to 20mA
0.1
%/mA
L1 = 100µH, VIN = 3.6V, ILOAD = 10mA
88
%
Efficiency
Feedback Set Point
VFB
Feedback Input Bias Current
IFB
1.225
VFB = 1.3V
1.25
1.275
V
5
100
nA
30.5
V
LX
LX Voltage Range
LX Switch Current Limit
LX On-Resistance
VLX
ILX(MAX)
RLX
LX Leakage Current
0.40
0.50
0.56
LIM = floating
0.20
0.25
0.285
LIM = GND
0.10
0.125
0.15
VCC = 5V, ILX = 100mA
0.8
VCC = 3.3V, ILX = 100mA
1
VLX = 30.5V
Maximum LX On-Time
tON
Minimum LX Off-Time
tOFF
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LIM = VCC
2
A
Ω
2
µA
µs
10
13
16
VFB > 1.1V
0.8
1.0
1.2
VFB < 0.8V (soft-start)
3.9
5.0
6.0
µs
Maxim Integrated │ 2
MAX1605
30V Internal Switch LCD Bias Supply
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)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CONTROL INPUTS
SHDN Input Threshold
SHDN Input Bias Current
VIH
2.4V ≤ VCC ≤ 5.5V
VIL
2.4V ≤ VCC ≤ 5.5V
ISHDN
VCC = 5.5V, VSHDN = 0 to 5.5V
LIM Input Low Level
2.4V ≤ VCC ≤ 5.5V
LIM Input Float Level
2.4V ≤ VCC ≤ 5.5V,
ILIM = ±0.5µA
LIM Input High Level
2.4V ≤ VCC ≤ 5.5V
LIM Input Bias Current
ILIM
SHDN = VCC, LIM = GND or VCC
0.8 x VCC
0.2 x VCC
-1
(VCC / 2)
- 0.2V
1
µA
0.4
V
(VCC / 2)
+ 0.2V
VCC - 0.4V
V
V
-2
SHDN = GND
V
2
0.1
1
µA
Electrical Characteristics
(VCC = SHDN = 3.3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
Inductor Input Voltage Range
SYMBOL
CONDITIONS
MIN
MAX
UNITS
VCC
(Note 2)
2.4
5.5
V
VIN
(Note 2)
0.8
VOUT
V
VCC falling, 50mV typical hysteresis
2.0
2.37
V
VFB = 1.3V
35
µA
SHDN = GND
1
µA
VCC Undervoltage Lockout
VUVLO
Quiescent Supply Current
ICC
Shutdown Supply Current
Feedback Set Point
VFB
Feedback Input Bias Current
IFB
1.215
VFB = 1.3V
1.285
V
100
nA
30.5
V
LX
LX Voltage Range
LX Switch Current Limit
LX On-Resistance
VLX
ILX(MAX)
RLX
LX Leakage Current
Maximum LX On-Time
Minimum LX Off-Time
LIM = VCC
0.35
0.58
LIM = floating
0.18
0.30
LIM = GND
0.08
0.17
VCC = 3.3V, ILX = 100mA
2
Ω
VLX = 30.5V
2
µA
µs
tON
tOFF
A
9
17
VFB > 1.1V
0.75
1.25
VFB < 0.8V
3.8
6.0
µs
CONTROL INPUTS
SHDN Input Threshold
SHDN Input Bias Current
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VIH
2.4V ≤ VCC ≤ 5.5V
VIL
2.4V ≤ VCC ≤ 5.5V
ISHDN
VCC = 5.5V, VSHDN = 0 to 5.5V
0. 8 x VCC
0.2 x VCC
-1
1
V
µA
Maxim Integrated │ 3
MAX1605
30V Internal Switch LCD Bias Supply
Electrical Characteristics (continued)
(VCC = SHDN = 3.3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
LIM Input Low Level
2.4V ≤ VCC ≤ 5.5V
LIM Input Float Level
2.4V ≤ VCC ≤ 5.5V,
ILIM = ±0.5µA
(VCC / 2)
- 0.25V
LIM Input High Level
2.4V ≤ VCC ≤ 5.5V
VCC - 0.4V
LIM Input Bias Current
SHDN = VCC, LIM = GND or VCC
ILIM
MAX
UNITS
0.4
V
(VCC / 2)
+ 0.25V
V
V
-2
2
SHDN = GND
µA
1
Note 1: All devices are 100% tested at TA = +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 VOUT.
Typical Operating Characteristics
(VCC = 3.3V, VIN = 3.6V, L1 = 10μH, SHDN = LIM = VCC, VOUT(NOM) = 18V (Figure 3), TA = +25°C, unless otherwise noted.)
17.9
IOUT = 1mA
17.8
20.9
20.7
20.5
20.3
IOUT = 1mA
20.1
19.7
17.6
2.5
3.0
3.5
4.0
4.5
5.0
LIM = GND
(125mA)
17.7
MAX1605 toc03
LIM = OPEN
(250mA)
17.5
3
6
9
12
0
5
10
15
20
LOAD CURRENT (mA)
EFFICIENCY vs. SUPPLY VOLTAGE
(L1 = 10µH)
EFFICIENCY vs. INPUT VOLTAGE
(L1 = 10µH)
EFFICIENCY vs. LOAD CURRENT
(L1 = 10µH)
IOUT = 1mA
80= 3.6V
VIN
ILIM = 500mA
72
IOUT = 1mA
60
50
VCC = 3.3V
ILIM = 500mA
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
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5.0
5.5
76
74
LIM = OPEN
(250mA)
72
70
68
LIM = VCC
(500mA)
LIM = GND
(125mA)
64
62
30
2.5
78
66
40
25
MAX1605 toc06
80
70
80
MAX1605 toc05
IOUT = 5mA
EFFICIENCY (%)
76
74
90
MAX1605 toc04
IOUT = 10mA
78
EFFICIENCY (%)
17.8
INPUT VOLTAGE (V)
IOUT = 5mA
2.0
17.9
SUPPLY VOLTAGE (V)
80
70
18.0
17.4
0
5.5
18.1
17.6
19.5
2.0
LIM = VCC
(500mA)
18.2
VCC = 3.3V
LIM = VCC
(500mA)
19.9
17.7
18.3
OUTPUT VOLTAGE (V)
IOUT = 5mA
IOUT = 5mA
21.1
OUTPUT VOLTAGE
vs. LOAD CURRENT
18.4
EFFICIENCY (%)
OUTPUT VOLTAGE (V)
18.0
21.3
OUTPUT VOLTAGE (V)
VIN = 3.6V
LIM = VCC
(500mA)
18.1
21.5
MAX1605 toc01
18.2
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1605 toc02
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
60
0
3
6
INPUT VOLTAGE (V)
9
12
0
5
10
15
20
25
LOAD CURRENT (mA)
Maxim Integrated │ 4
MAX1605
30V Internal Switch LCD Bias Supply
Electrical Characteristics (continued)
(VCC = 3.3V, VIN = 3.6V, L1 = 10μH, SHDN = LIM = VCC, VOUT(NOM) = 18V (Figure 3), TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(L1 = 100µH)
78
LIM = GND
100
5
10
15
20
0
25
5
10
15
20
25
LOAD CURRENT (mA)
LOAD CURRENT (mA)
CURRENT LIMIT vs. INPUT VOLTAGE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (NO-LOAD)
400
LIM = OPEN
300
200
100
20
15
10
6
9
12
INPUT VOLTAGE (V)
LINE TRANSIENT
1
2
3
4
LOAD TRANSIENT
6V
0
2V
18.1V
18.1V
17.9V
17.9V
1.5
1.0
LIM = VCC
(500mA)
0
500mA
0
5
10
15
20
25
LOAD CURRENT (mA)
SHUTDOWN WAVEFORM
MAX1605 toc14
MAX1605 toc15
4V
IL1
500mA/div
B
100mV/div
18V
18
5.5
LIM = OPEN
(250mA)
2.0
5
VOUT
100mV/div
A
2V/div
10mA
4V
5.0
LIM = GND
(125mA)
2.5
SUPPLY VOLTAGE (V)
MAX1605 toc13
4.5
0
0
IOUT
10mA/div
3
4.0
0.5
0
0
3.5
SUPPLY CURRENT vs. LOAD CURRENT
5
LIM = GND
3.0
3.0
SUPPLY CURRENT (mA)
500
SUPPLY CURRENT (µA)
LIM = VCC
2.5
SUPPLY VOLTAGE (V)
25
MAX1605 toc10
600
2.0
MAX1605 toc11
0
LIM = OPEN
200
74
74
CURRENT LIMIT (mA)
LIM = VCC
(500mA)
76
300
MAX1605 toc12
LIM = VCC
(500mA)
76
80
400
VSHDN
2V/div
78
82
2V
0
500mA
IL1
250mA/div
80
LIM = GND
(125mA)
84
LIM = VCC
500
250mA
0
20V
VOUT
10V/div
LIM = GND
(125mA)
82
LIM = OPEN
(250mA)
CURRENT LIMIT (mA)
86
LIM = OPEN
(250mA)
84
88
EFFICIENCY (%)
EFFICIENCY (%)
86
600
MAX1605 toc08
88
CURRENT LIMIT vs. SUPPLY VOLTAGE
90
MAX1605 toc07
90
MAX1605 toc09
EFFICIENCY vs. LOAD CURRENT
(L1 = 47µH)
10V
0
200µs/div
A: VIN = VCC = 2.4V TO 5.5V
B: VOUT = 18V, ROUT = 3.6kΩ
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40µs/div
VOUT = 18V, IOUT = 1mA TO 10mA
VCC = 3.3V, VIN = 3.6V
200µs/div
VOUT = 18V, ROUT = 1.8kΩ
VCC = 3.3V, VIN = 3.6V
Maxim Integrated │ 5
MAX1605
30V Internal Switch LCD Bias Supply
Pin Description
PIN
NAME
FUNCTION
1
SHDN
2
VCC
IC Supply Voltage (+2.4V to +5.5V). Bypass VCC to GND with a 0.1µF or greater capacitor.
3
GND
Ground
4
LX
Inductor Connection. The drain of an internal 30V N-channel MOSFET.
LX is high impedance in shutdown.
5
LIM
Inductor Current Limit Selection. Connect LIM to VCC for 500mA, leave LIM floating for 250mA,
or connect LIM to GND for 125mA.
6
FB
Feedback Input. Connect to a resistive-divider network between the output (VOUT) and FB to set the
output voltage between VIN and 30V. The feedback threshold is 1.25V.
Active-Low Shutdown Input. A logic low shuts down the device and reduces the supply current to
0.1µA. Connect SHDN to VCC for normal operation.
L1
10µH
VIN = 0.8V TO VOUT
VOUT = VIN TO 30V
LX
COUT
CFF
VCC = 2.4V TO 5.5V
CONTROL
LOGIC
VCC
LIM
N
CURRENT
LIMIT
R1
SHUTDOWN
LOGIC
SHDN
ON
FB
ERROR
AMPLIFIER
OFF
R2
1.25V
MAX1605
GND
Figure 1. Functional Diagram
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.
www.maximintegrated.com
Control Scheme
The MAX1605 features a minimum off-time, currentlimited 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
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).
Maxim Integrated │ 6
MAX1605
30V Internal Switch LCD Bias Supply
VCC
(2.4V TO 5.5V)
VCC
(2.4V TO 5.5V)
VCC
VCC
MAX1605
LIM
VCC
(2.4V TO 5.5V)
VCC
MAX1605
NO CONNECTION
GND
IPEAK = 500mA
MAX1605
LIM
LIM
GND
GND
IPEAK = 250mA
IPEAK = 125mA
Figure 2. Setting the Peak Inductor Current Limit
Setting the Output Voltage (FB)
Adjust the output voltage by connecting a voltage-divider
from the output (VOUT) to FB (Figure 3). Select R2
between 10kΩ to 200kΩ. Calculate R1 with the following
equation:
R1 = R2 [(VOUT / VFB) – 1]
where VFB = 1.25V and VOUT may range from VIN to
30V. 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 space-sensitive,
low-power applications. Connect LIM to VCC 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 VIN when
the MAX1605 is shut down. The capacitance and load at
OUT determine the rate at which VOUT decays. SHDN
can be pulled as high as 6V, regardless of the input and
output voltages.
www.maximintegrated.com
Separate/Same Power for L1 and VCC
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 30V)
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, VIN and VCC can also be supplied from one supply if it remains within VCC’s operating
limits (+2.4V to +5.5V).
L1
10µH
VIN = 0.8V TO VOUT
CIN
10µF
VCC = 2.4V TO 5.5V
C1
0.1µF
LX
VCC
MAX1605
LIM
D1 VOUT = 18V
R1
2.2MΩ
CFF
10pF
COUT
1µF
FB
R2
165kΩ
ON
OFF
SHDN
GND
Figure 3. Typical Application Circuit
Maxim Integrated │ 7
MAX1605
30V Internal Switch LCD Bias Supply
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 (ILX(MAX)) required for the
application may be calculated from the following equation:
ILX ( MAX ) ≥
(
)
VOUT − VIN( MIN ) × t OFF( MIN )
VOUT × I OUT ( MAX )
+
VIN( MIN )
2×L
where tOFF(MIN) = 0.8μs, and VIN(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 the Current Limit Select
Pin (LIM) section 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.
www.maximintegrated.com
Surface-mount capacitors are generally preferred because
they lack the inductance and resistance of their throughhole equivalents.
Input Bypass Capacitor
Two inputs, VCC and VIN, require bypass capacitors.
Bypass VCC with 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.
Maxim Integrated │ 8
MAX1605
30V Internal Switch LCD Bias Supply
L1
10µH
VIN =
0.8V TO
VOUT
VCC =
2.4V TO
5.5V
R3
1Ω
C3
0.1µF
D1*
C5
1µF
D2*
VNEG
-19V
C2
1µF
D3**
VCC
C6
0.1µF
LX
MAX1605
LIM
C4
0.01µF
C1
1000pF
R1
240kΩ
FB
R2
16.5kΩ
ON
OFF
SHDN
GND
*D1, D2 = CENTRAL SEMICONDUCTOR
CMPD7000 DUAL
**D3 = CENTRAL SEMICONDUCTOR
CMSD4448 (1N4148)
Figure 4. Negative Voltage for LCD Bias
Output Disconnected in Shutdown
L1
10µH
VIN = 0.8V TO VOUT
R3 = 180kΩ
VSET = 18.3V
(VOUT + 0.3V)
VCC = 2.4V TO 5.5V
LX
VCC
MAX1605
LIM
R1
FB
R2
ON
SHDN
VOUT = 18V
2N2907A
GND
OFF
When the MAX1605 is shut down, the output remains
connected to the input (Figure 3), so the output voltage falls to approximately VIN - 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
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 5. Output Disconnected in Shutdown
Chip Information
TRANSISTOR COUNT: 2329
www.maximintegrated.com
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that
a “+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
6 SOT23
U6F+6
21-0058
90-0175
6 TDFN
T633+2
21-0137
90-0058
Maxim Integrated │ 9
MAX1605
30V Internal Switch LCD Bias Supply
Revision History
REVISION
NUMBER
REVISION
DATE
2
8/18
DESCRIPTION
Updated Ordering Information and Packaging Information
PAGES
CHANGED
1, 10
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2018 Maxim Integrated Products, Inc. │ 10