Maxim MAX1722 1.5î¼a iq, step-up dc-dc converters in thin sot23-5 Datasheet

MAX1722/MAX1723/
MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
General Description
The MAX1722/MAX1723/MAX1724 compact, high-efficiency, step-up DC-DC converters are available in tiny, 5pin thin SOT23 packages. They feature an extremely low
1.5µA quiescent supply current to ensure the highest possible light-load efficiency. Optimized for operation from
one to two alkaline or nickel-metal-hydride (NiMH) cells, or
a single Li+ cell, these devices are ideal for applications
where extremely low quiescent current and ultra-small size
are critical.
Built-in synchronous rectification significantly improves
efficiency and reduces size and cost by eliminating the
need for an external Schottky diode. All three devices feature a 0.5Ω N-channel power switch. The MAX1722/
MAX1724 also feature proprietary noise-reduction circuitry,
which suppresses electromagnetic interference (EMI)
caused by the inductor in many step-up applications. The
family offers different combinations of fixed or adjustable
outputs, shutdown, and EMI reduction (see Selector
Guide).
Applications
Pagers
Remote Controls
Remote Wireless
Transmitters
Personal
Medical Devices
Digital Still Cameras
Features
o
o
o
o
o
o
o
o
o
o
o
Up to 90% Efficiency
No External Diode or FETs Needed
1.5µA Quiescent Supply Current
0.1µA Logic-Controlled Shutdown
±1% Output Voltage Accuracy
Fixed Output Voltage (MAX1724) or Adjustable
Output Voltage (MAX1722/MAX1723)
Up to 150mA Output Current
0.8V to 5.5V Input Voltage Range
0.91V Guaranteed Startup (MAX1722/MAX1724)
Internal EMI Suppression (MAX1722/MAX1724)
Thin SOT23-5 Package (1.1mm max Height)
Ordering Information
PART
TEMP RANGE
PINPACKAGE
TOP
MARK
Single-Cell BatteryPowered Devices
Low-Power Hand-Held
Instruments
MP3 Players
MAX1722EZK+T+
-40°C to +85°C
5 SOT23
ADQF
MAX1723EZK+T
-40°C to +85°C
5 SOT23
ADQG
MAX1724EZK27+T
MAX1724EZK30+T
-40°C to +85°C
5 SOT5
ADQH
-40°C to +85°C
5 SOT23
ADQI
MAX1724EZK33+T
-40°C to +85°C
5 SOT23
ADQJ
Personal Digital
Assistants (PDA)
MAX1724EZK50+T
-40°C to +85°C 5 SOT23
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
ADQK
Selector Guide appears at end of data sheet.
Typical Operating Circuit
Pin Configurations
TOP VIEW
10µH
+
BATT
IN
0.8V TO 5.5V
BATT
1
5
LX
4
OUT
LX
GND 2
MAX1724
MAX1722
OUT
OUT
ON
OFF
SHDN
GND
3.3V AT
UP TO 150mA
FB 3
THIN SOT23
Pin Configurations are continued at end of data sheet.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-1735; Rev 1; 9/12
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
ABSOLUTE MAXIMUM RATINGS
OUT, SHDN, BATT, LX to GND ................................-0.3V to +6V
FB to GND ................................................-0.3V to (VOUT + 0.3V)
OUT, LX Current.......................................................................1A
Continuous Power Dissipation (TA = +70°C)
5-Pin Thin SOT23 (derate 7.1mW/°C above +70°C) ...571mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Soldering Temperature
Lead(Pb)-Free packages..............................................+260°C
Packages Containing Lead(Pb)....................................+240°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
(VBATT = 1.2V, VOUT = 3.3V (MAX1722/MAX1723), VOUT = VOUT(NOM) (MAX1724), SHDN = OUT, RL = ∞, TA = 0°C to +85°C,
unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Minimum Input Voltage
Operating Input Voltage
CONDITIONS
VIN
TA = +25°C
TA = +25°C,
RL = 3kΩ
MAX1724EZK27
MAX1724EZK30
VOUT
MAX1724EZK33
MAX1724EZK50
Output Voltage Range
2
TYP
MAX
0.8
MAX1722/MAX1724
Minimum Startup Input Voltage
Output Voltage
MIN
V
MAX1722/MAX1724
0.91
5.5
MAX1723 (Note 2)
1.2
5.5
MAX1722/MAX1724
0.83
0.91
MAX1723 (Note 2)
0.87
1.2
2.7
UNITS
TA = +25°C
2.673
TA = 0°C to +85°C
2.633
TA = +25°C
2.970
TA = 0°C to +85°C
2.925
TA = +25°C
3.267
TA = 0°C to +85°C
3.218
TA = +25°C
4.950
TA = 0°C to +85°C
4.875
5.125
2
5.5
V
V
2.727
2.767
3.0
3.030
3.075
3.3
3.333
V
3.383
5.0
5.050
VOUT
MAX1722/MAX1723
Feedback Voltage
VFB
MAX1722/MAX1723
Feedback Bias Current
IFB
MAX1722/MAX1723
N-Channel On-Resistance
RDS(ON)
VOUT forced to 3.3V
0.5
1.0
Ω
P-Channel On-Resistance
RDS(ON)
VOUT forced to 3.3V
1.0
2.0
Ω
N-Channel Switch Current Limit
ILIM
VOUT forced to 3.3V
400
500
600
mA
Switch Maximum On-Time
tON
3.5
5
6.5
µs
5
20
35
mA
µA
Synchronous Rectifier ZeroCrossing Current
VOUT forced to 3.3V
Quiescent Current into OUT
(Notes 3, 4)
TA = +25°C
1.223
TA = 0°C to +85°C
1.210
1.235
1.247
1.260
TA = +25°C
1.5
TA = +85°C
2.2
20
1.5
3.6
0.01
0.5
Shutdown Current into OUT
MAX1723/MAX1724
(Notes 3, 4)
TA = +25°C
TA = +85°C
0.1
Quiescent Current into BATT
MAX1722/MAX1724
(Note 4)
TA = +25°C
0.001
TA = +85°C
0.01
0.5
V
V
nA
µA
µA
Maxim Integrated
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 1.2V, VOUT = 3.3V (MAX1722/MAX1723), VOUT = VOUT(NOM) (MAX1724), SHDN = OUT, RL = ∞, TA = 0°C to +85°C,
unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Shutdown Current into BATT
SHDN Voltage Threshold
CONDITIONS
MAX1724 (Note 4)
VIL
MAX1723/MAX1724
VIH
MAX1723/MAX1724
MAX1723/MAX1724,
V SHDN = 5.5V
SHDN Input Bias Current
MIN
TYP
MAX
TA = +25°C
0.001
0.5
TA = +85°C
0.01
75
400
500
800
TA = +25°C
2
100
TA = +85°C
7
UNITS
µA
mV
nA
ELECTRICAL CHARACTERISTICS
(VBATT = 1.2V, VOUT = 3.3V (MAX1722/MAX1723), VOUT = VOUT(NOM) (MAX1724), SHDN = OUT, RL = ∞, TA = -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Output Voltage
Output Voltage Range
SYMBOL
VOUT
CONDITIONS
MIN
TYP
MAX
MAX1724EZK27
2.633
2.767
MAX1724EZK30
2.925
3.075
MAX1724EZK33
3.218
3.383
MAX1724EZK50
4.875
5.125
UNITS
V
VOUT
MAX1722/MAX1723
2
5.5
VFB
MAX1722/MAX1723
1.200
1.270
V
N-Channel On-Resistance
RDS(ON)
VOUT forced to 3.3V
1.0
Ω
P-Channel On-Resistance
Feedback Voltage
RDS(ON)
VOUT forced to 3.3V
N-Channel Switch Current Limit
ILIM
VOUT forced to 3.3V
Switch Maximum On-Time
tON
Synchronous Rectifier ZeroCrossing Current
VOUT forced to 3.3V
Quiescent Current into OUT
SHDN Voltage Threshold
2.0
Ω
400
620
mA
3.5
6.5
µs
5
35
mA
3.6
µA
(Notes 3,4)
VIL
MAX1723/MAX1724
VIH
MAX1723/MAX1724
V
75
800
mV
Note 1: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2: Guaranteed with the addition of a Schottky MBR0520L external diode between LX and OUT when using the MAX1723
with only one cell, and assumes a 0.3V voltage drop across the Schottky diode (see Figure 3).
Note 3: Supply current is measured with an ammeter between the output and OUT pin. This current correlates directly with actual
battery supply current, but is reduced in value according to the step-up ratio and efficiency.
Note 4: VOUT forced to the following conditions to inhibit switching: VOUT = 1.05 VOUT(NOM) (MAX1724), VOUT = 3.465V
(MAX1722/MAX1723).
Maxim Integrated
3
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
Typical Operating Characteristics
(Figure 3 (MAX1723), Figure 7 (MAX1722), Figure 8 (MAX1724), VBATT = VIN = 1.5V, L = 10µH, CIN = 10µF, COUT = 10µF, TA = +25°C,
unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5.0V)
(VOUT = 2.5V)
(VOUT = 3.3V)
70
VIN = 1.0V
60
80
70
60
L = DO1606
0.1
1
10
100
1000
0.1
VIN = 1.0V
1
10
100
0.01
1000
0.1
1
10
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
STARTUP VOLTAGE
vs. LOAD CURRENT
QUIESCENT CURRENT INTO OUT
vs. OUTPUT VOLTAGE
VOUT = 5.0V
80
VOUT = 3.3V
2.0
1.8
1.6
1.4
1.2
1.0
40
0.8
0
3
4
5
1.4
1.2
1.0
0.8
0.6
0.4
0
0.01
0.1
INPUT VOLTAGE (V)
1
10
LOAD CURRENT (mA)
STARTUP VOLTAGE vs.
TEMPERATURE
NO LOAD
1.0
100
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
OUTPUT VOLTAGE (V)
SWITCHING WAVEFORMS
MAX1722 toc07
1.2
STARTUP VOLTAGE (V)
1.6
MAX1722 toc08
2
NO LOAD
1.8
0.2
0.6
1
2.0
QUIESCENT CURRENT (µA)
120
2.2
STARTUP VOLTAGE (V)
160
RESISTIVE LOAD
VOUT = 5.0V
1000
MAX1722 toc06
2.4
MAX1722 toc04
VOUT = 2.5V
0
L = DO1606
50
LOAD CURRENT (mA)
200
IOUT(MAX) (mA)
0.01
70
MAX1722 toc05
0.01
VIN = 1.5V
L = DO1606
VIN = 1.5V
50
VIN = 2.0V
80
60
VIN = 1.0V
VIN = 1.5V
50
90
EFFICIENCY (%)
80
VIN = 2.5V
VIN = 2.0V
90
100
MAX1722 toc03
100
EFFICIENCY (%)
VIN = 4.0V
MAX1722 toc02
VIN = 2.0V
90
EFFICIENCY (%)
VIN = 3.3V
MAX1722 toc01
100
0.8
ILX
500mA/div
VOUT
50mV/div
0.6
0.4
VLX
2V/div
0.2
0
-40
-15
10
35
TEMPERATURE (°C)
4
60
85
1µs/div
IOUT = 50mA, VOUT = 5.0V, VIN = 3.3V
Maxim Integrated
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
Typical Operating Characteristics (continued)
(Figure 3 (MAX1723), Figure 7 (MAX1722), Figure 8 (MAX1724), VBATT = VIN = 1.5V, L = 10µH, CIN = 10µF, COUT = 10µF, TA = +25°C,
unless otherwise noted.)
SHUTDOWN RESPONSE
3.3V
MAX1722 toc10
MAX1722 toc09
LOAD-TRANSIENT RESPONSE
5V
A
VOUT
2V/div
0
50mA
2V
VSHDN
1V/div
B
0
0
A: VOUT, 50mV/div
B: IOUT, 20mA/div
1ms/div
VIN = 3.3V, VOUT = 5.0V, ROUT = 100Ω
200µs/div
SHUTDOWN INPUT THRESHOLD
vs. TEMPERATURE
MAX1722 toc11
0.8
SHUTDOWN THRESHOLD (mV)
0.7
0.6
RISING EDGE
0.5
0.4
FALLING EDGE
0.3
0.2
0.1
0
-40
-15
10
35
60
85
TEMPERATURE (°C)
Pin Description
PIN
NAME
FUNCTION
MAX1722
MAX1723
MAX1724
1
—
1
BATT
Battery Input and Damping Switch Connection
—
1
3
SHDN
Shutdown Input. Drive high for normal operation. Drive low for shutdown.
2
2
2
GND
Ground
3
3
—
FB
4
4
4
OUT
5
5
5
LX
Maxim Integrated
Feedback Input to Set Output Voltage. Use a resistor-divider network to
adjust the output voltage. See Setting the Output Voltage section.
Power Output. OUT also provides bootstrap power to the IC.
Internal N-channel MOSFET Switch Drain and P-Channel Synchronous
Rectifier Drain
5
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
OUT
MAX1723
ZEROCROSSING
DETECTOR
STARTUP
CIRCUITRY
P
SHDN
CONTROL
LOGIC
DRIVER
LX
FB
ERROR
COMPARATOR
1.235V REFERENCE
N
CURRENT
LIMIT
GND
Figure 1. MAX1723 Simplified Functional Diagram
Detailed Description
The MAX1722/MAX1723/MAX1724 compact, high-efficiency, step-up DC-DC converters are guaranteed to
start up with voltages as low as 0.91V and operate with
an input voltage down to 0.8V. Consuming only 1.5µA of
quiescent current, these devices include a built-in synchronous rectifier that reduces cost by eliminating the
need for an external diode and improves overall efficiency by minimizing losses in the circuit (see Synchronous
Rectification section). The MAX1722/MAX1724 feature a
clamp circuit that reduces EMI due to inductor ringing.
The MAX1723/MAX1724 feature an active-low shutdown
that reduces quiescent supply current to 0.1µA. The
MAX1722/MAX1723 have an adjustable output voltage,
while the MAX1724 is available with four fixed-output
voltage options (see Selector Guide). Figure 1 is the
MAX1723 simplified functional diagram and Figure 2 is
the MAX1724 simplified functional diagram.
PFM Control Scheme
A forced discontinuous, current-limited, pulse-frequencymodulation (PFM) control scheme is a key feature of the
6
MAX1722/MAX1723/MAX1724. This scheme provides
ultra-low quiescent current and high efficiency over a
wide output current range. There is no oscillator; the
inductor current is limited by the 0.5A N-channel current limit or by the 5µs switch maximum on-time.
Following each on cycle, the inductor current must
ramp to zero before another cycle may start. When the
error comparator senses that the output has fallen
below the regulation threshold, another cycle begins.
Synchronous Rectification
The internal synchronous rectifier eliminates the need
for an external Schottky diode, thus reducing cost and
board space. While the inductor discharges, the Pchannel MOSFET turns on and shunts the MOSFET
body diode. As a result, the rectifier voltage drop is significantly reduced, improving efficiency without the
addition of external components.
Low-Voltage Startup Circuit
The MAX1722/MAX1723/MAX1724 contain a low-voltage startup circuit to control DC-DC operation until the
output voltage exceeds 1.5V (typ). The minimum startMaxim Integrated
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
DAMPING
SWITCH
BATT
OUT
MAX1724
ZEROCROSSING
DETECTOR
STARTUP
CIRCUITRY
R2
P
SHDN
CONTROL
LOGIC
DRIVER
ERROR
COMPARATOR
LX
N
R1
CURRENT
LIMIT
1.235V REFERENCE
GND
Figure 2. MAX1724 Simplified Functional Diagram
10µH
1.2V TO VOUT
D1
10µF
SHDN
LX
OUT
R2
2.37MΩ
MAX1723
GND
VOUT = 3.6V
10µF
FB
Shutdown (MAX1723/MAX1724)
R1
1.24MΩ
Figure 3. MAX1723 Single-Cell Operation
up voltage is a function of load current (see Typical
Operating Characteristics). This circuit is powered from
the BATT pin for the MAX1722/MAX1724, guaranteeing
startup at input voltages as low as 0.91V. The MAX1723
Maxim Integrated
lacks a BATT pin; therefore, this circuit is powered
through the OUT pin. Adding a Schottky diode in parallel with the P-channel synchronous rectifier allows for
startup voltages as low as 1.2V for the MAX1723
(Figure 3). The external Schottky diode is not needed
for input voltages greater than 1.8V. Once started, the
output maintains the load as the battery voltage
decreases below the startup voltage.
The MAX1723/MAX1724 enter shutdown when the
SHDN pin is driven low. During shutdown, the body
diode of the P-channel MOSFET allows current to flow
from the battery to the output. VOUT falls to approximately VIN - 0.6V and LX remains high impedance.
Shutdown can be pulled as high as 6V, regardless of
the voltage at BATT or OUT. For normal operation, connect SHDN to the input.
7
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
VOUT
VIN
MAX1722
MAX1724
PDRV
OUT
P
BATT
DAMPING
SWITCH
TIMING
CIRCUIT
DAMP
LX
NDRV
N
GND
Figure 4. Simplified Diagram of Damping Switch
1V/div
1V/div
1µs/div
1µs/div
Figure 5. LX Ringing Without Damping Switch (MAX1723)
Figure 6. LX Ringing With Damping Switch (MAX1722/MAX1724)
Design Procedure
BATT/Damping Switch
(MAX1722/MAX1724)
The MAX1722/MAX1724 include an internal damping
switch (Figure 4) to minimize ringing at LX and reduce
EMI. When the energy in the inductor is insufficient to
supply current to the output, the capacitance and
inductance at LX form a resonant circuit that causes
ringing. The damping switch supplies a path to quickly
dissipate this energy, suppressing the ringing at LX.
This does not reduce the output ripple, but does
reduce EMI with minimal impact on efficiency. Figures
5 and 6 show the LX node voltage waveform without
and with the damping switch, respectively.
8
Setting the Output Voltage
(MAX1722/MAX1723)
The output voltage can be adjusted from 2V to 5.5V
using external resistors R1 and R2 (Figure 7). Since FB
leakage is 20nA (max), select feedback resistor R1 in
the 100kΩ to 1MΩ range. Calculate R2 as follows:
⎛V
⎞
R2 = R1 ⎜ OUT − 1⎟
⎝ VFB
⎠
where VFB = 1.235V.
Maxim Integrated
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
INPUT
0.8V TO VOUT
10µF
For maximum output current, choose the inductor value
so that the controller reaches the current-limit before
the maximum on-time is triggered:
10µH
OUT
MAX1722
L<
OUTPUT
2V TO 5.5V
LX
BATT
R2
10µF
VBATT t ON(MAX)
ILIM
where the maximum on-time is typically 5µs, and the
current limit (ILIM) is typically 500mA (see Electrical
Characteristics table).
FB
R1
GND
For larger inductor values, determine the peak inductor
current (IPEAK) by:
IPEAK =
VBATT t ON(MAX)
L
Figure 7. Adjustable Output Circuit
Inductor Selection
The control scheme of the MAX1722/MAX1723/
MAX1724 permits flexibility in choosing an inductor. A
10µH inductor value performs well in most applications.
Smaller inductance values typically offer smaller physical size for a given series resistance, allowing the
smallest overall circuit dimensions. Circuits using larger
inductance values may start up at lower battery voltages, provide higher efficiency, and exhibit less ripple,
but they may reduce the maximum output current. This
occurs when the inductance is sufficiently large to prevent the maximum current limit (I LIM ) from being
reached before the maximum on-time (t ON(MAX) )
expires.
Table 1. Suggested Inductors and
Suppliers
INPUT
0.8V TO VOUT
10µH
C1
10µF
BATT
LX
OUT
OUTPUT
VOUT (NOM)
MAX1724
C2
10µF
ON
OFF
SHDN
GND
Figure 8. MAX1724 Standard Application Circuit
The inductor’s incremental 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. Table 1 lists suggested inductors and suppliers.
INDUCTOR
PHONE
WEBSITE
Coilcraft
DO1608 Series
DO1606 Series
847-639-2361
www.coilcraft.com
Murata
LQH4C Series
770-436-1300
www.murata.com
Maximum Output Current
CDRH4D18 Series
CR32 Series
CMD4D06 Series
847-545-6700
www.sumida.com
The maximum output current depends on the peak inductor current, the input voltage, the output voltage, and the
overall efficiency (η):
CXLD140 Series
+81 (06) 6355-5733
www.daidoo.co.jp
3DF Type
D412F Type
847-297-0070
www.toko.com
MANUFACTURER
Sumida
Sumitomo/
Daidoo Electronics
Toko
Maxim Integrated
IOUT(MAX) =
⎛V
⎞
1
IPEAK ⎜ BATT ⎟ η
2
⎝ VOUT ⎠
9
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
Table 2. Suggested Surface-Mount Capacitors and Manufacturers (C1 and C2)
MANUFACTURER
AVX
CAPACITOR
VALUE
DESCRIPTION
1µF to 10µF
X7R Ceramic
10µF to 330µF
TAJ Tantalum Series
TPS Tantalum Series
PHONE
WEBSITE
843-448-9411
www.avxcorp.com
1µF to 22µF
X5R/X7R Ceramic
10µF to 330µF
T494 Tantalum Series
68µF to 330µF
T520 Tantalum Series
Sanyo
33µF to 330µF
TPC Polymer Series
408-749-9714
www.secc.co.jp
Taiyo Yuden
33µF to 330µF
X5R/X7R Ceramic
800-368-2496
www.t-yuden.org
1µF to 10µF
X7R Ceramic
847-803-6100
www.tdk.com
10µF to 330µF
594D Tantalum Series
595D Tantalum Series
203-452-5664
www.vishay.com
Kemet
TDK
Vishay Sprague
For most applications, the peak inductor current equals
the current limit. However, for applications using large
inductor values or low input voltages, the maximum ontime limits the peak inductor current (see Inductor
Selection section).
Capacitor Selection
Choose input and output capacitors to supply the input
and output peak currents with acceptable voltage ripple. The input filter capacitor (CIN) reduces peak currents drawn from the battery and improves efficiency.
Low equivalent series resistance (ESR) capacitors are
recommended. Ceramic capacitors have the lowest
ESR, but low ESR tantalum or polymer capacitors offer
a good balance between cost and performance.
Output voltage ripple has two components: variations
in the charge stored in the output capacitor with each
LX pulse, and the voltage drop across the capacitor’s
ESR caused by the current into and out of the capacitor:
864-963-6300
www.kemet.com
where IPEAK is the peak inductor current (see Inductor
Selection section). For ceramic capacitors, the output
voltage ripple is typically dominated by VRIPPLE(C). For
example, a 10µF ceramic capacitor and a 10µH inductor typically provide 75mV of output ripple when stepping up from 3.3V to 5V at 50mA. Low input-to-output
voltage differences (i.e. two cells to 3.3V) require higher output capacitor values.
Capacitance and ESR variation of temperature should
be considered for best performance in applications
with wide operating temperature ranges. Table 2 lists
suggested capacitors and suppliers.
PC Board Layout Considerations
Careful PC board layout is important for minimizing
ground bounce and noise. Keep the IC’s GND pin and
the ground leads of the input and output capacitors
less than 0.2in (5mm) apart using a ground plane. In
addition,
keep
all
connections
to
FB
(MAX1722/MAX1723 only) and LX as short as possible.
VRIPPLE = VRIPPLE(C) + VRIPPLE(ESR)
VRIPPLE(ESR) ≈ IPEAK RESR(COUT)
VRIPPLE(C) ≈
10
⎞
1⎛
L
(IPEAK2 - IOUT2 )
⎜
2 ⎝ (VOUT - VBATT )COUT ⎟⎠
Maxim Integrated
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
Pin Configurations (continued)
TOP VIEW
SHDN
1
GND 2
5
LX
BATT 1
MAX1723
4
OUT
SHDN
3
THIN SOT23
OUTPUT
(V)
SHDN
LX
DAMPING
MAX1722EZK
Adjustable
No
Yes
MAX1723EZK
Adjustable
Yes
No
MAX1724EZK27
Fixed 2.7
Yes
Yes
MAX1724EZK30
Fixed 3.0
Yes
Yes
MAX1724EZK33
Fixed 3.3
Yes
Yes
MAX1724EZK50
Fixed 5.0
Yes
Yes
Maxim Integrated
4
OUT
THIN SOT23
Package Information
Selector Guide
PART
LX
MAX1724
GND 2
FB 3
5
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.
SOT23
Z5+1
21-0013
90-0241
11
MAX1722/MAX1723/MAX1724
1.5µA IQ, Step-Up DC-DC Converters
in Thin SOT23-5
Revision History
REVISION
NUMBER
REVISION
DATE
0
7/01
Initial release
1
9/12
Added lead-free and tape-and-reel designations and added soldering
temperatures
DESCRIPTION
PAGES
CHANGED
—
1, 2
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. 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.
12 ________________________________Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2012 Maxim Integrated Products, Inc.
The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.