MAX1722ELT+ [MAXIM]
暂无描述;
| 型号： | MAX1722ELT+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 暂无描述 转换器 |
| 文件： | 总12页 (文件大小：292K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1735; Rev 0; 7/01
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
General Description
Features
The MAX1722/MAX1723/MAX1724 compact, high-effi-
ciency, step-up DC-DC converters are available in tiny, 5-
pin thin SOT23 packages. They feature an extremely low
1.5µA quiescent supply current to ensure the highest pos-
sible 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.
o Up to 90% Efficiency
o No External Diode or FETs Needed
o 1.5µA Quiescent Supply Current
o 0.1µA Logic-Controlled Shutdown
o
1% ꢀutput ꢁoltage Accuracy
o Fixed ꢀutput ꢁoltage (MAX1724) or Adjustable
ꢀutput ꢁoltage (MAX1722/MAX1723)
o Up to 150mA ꢀutput Current
Built-in synchronous rectification significantly improves
efficiency and reduces size and cost by eliminating the
need for an external Schottky diode. All three devices fea-
ture 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).
o 0.8ꢁ to 5.5ꢁ Input ꢁoltage Range
o 0.91ꢁ Guaranteed Startup (MAX1722/MAX1724)
o Internal EMI Suppression (MAX1722/MAX1724)
o Thin SꢀT23-5 Package (1.1mm max Height)
Ordering Information
PIN-
TꢀP
PART
TEMP. RANGE
PACKAGE MARK
MAX1722EZK-T
MAX1723EZK-T
MAX1724EZK27-T
MAX1724EZK30-T
MAX1724EZK33-T
MAX1724EZK50-T
-40°C to +85°C 5 SOT23
-40°C to +85°C 5 SOT23
-40°C to +85°C 5 SOT23
-40°C to +85°C 5 SOT23
-40°C to +85°C 5 SOT23
-40°C to +85°C 5 SOT23
ADQF
ADQG
ADQH
ADQI
Applications
Pagers
Single-Cell Battery-
Powered Devices
Remote Controls
ADQJ
ADQK
Low-Power Hand-Held
Instruments
Remote Wireless
Transmitters
MP3 Players
Personal
Medical Devices
Selector Guide
Personal Digital
Assistants (PDA)
LX
DAMPING
Digital Still Cameras
PART
ꢀUTPUT (ꢁ)
SHDN
MAX1722EZK
Adjustable
Adjustable
Fixed 2.7
Fixed 3.0
Fixed 3.3
Fixed 5.0
No
Yes
No
MAX1723EZK
Yes
Yes
Yes
Yes
Yes
MAX1724EZK27
MAX1724EZK30
MAX1724EZK33
MAX1724EZK50
Yes
Yes
Yes
Yes
Typical Operating Circuit
Pin Configurations
10µH
TOP VIEW
IN
BATT
LX
0.8V TO 5.5V
BATT
GND
FB
1
2
3
5
LX
MAX1724
MAX1722
OUT
OUT
ON
3.3V AT
UP TO 150mA
SHDN
OFF
4
OUT
GND
THIN SꢀT23-5
Pin Configurations are continued at end of data sheet.
________________________________________________________________ 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.
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
ABSꢀLUTE MAXIMUM RATINGS
OUT, SHDN, BATT, LX to GND ................................-0.3V to +6V
FB to GND ................................................-0.3V to (V + 0.3V)
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
OUT
OUT, LX Current.......................................................................1A
Continuous Power Dissipation (T = +70°C)
A
5-Pin Thin SOT23 (derate 7.1mW/°C above +70°C)...571mW
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
= 1.2V, V
= 3.3V (MAX1722/MAX1723), V
= V
(MAX1724), SHDN = OUT, R = ∞, T = 0°C to +85°C,
OUT(NOM) L A
BATT
OUT
OUT
unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBꢀL
CꢀNDITIꢀNS
MAX1722/MAX1724
MIN
TYP
MAX
UNITS
Minimum Input Voltage
0.8
V
MAX1722/MAX1724
0.91
1.2
5.5
5.5
Operating Input Voltage
V
T
= +25°C
V
V
IN
A
MAX1723 (Note 2)
MAX1722/MAX1724
MAX1723 (Note 2)
0.83
0.87
2.7
0.91
1.2
T
A
= +25°C,
Minimum Startup Input Voltage
R = 3kΩ
L
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
= +25°C
2.673
2.633
2.970
2.925
3.267
3.218
4.950
4.875
2
2.727
2.767
3.030
3.075
3.333
3.383
5.050
5.125
5.5
MAX1724EZK27
MAX1724EZK30
MAX1724EZK33
= 0°C to +85°C
= +25°C
3.0
3.3
5.0
= 0°C to +85°C
= +25°C
Output Voltage
V
V
V
OUT
= 0°C to +85°C
= +25°C
MAX1724EZK50
= 0°C to +85°C
Output Voltage Range
Feedback Voltage
MAX1722/MAX1723
MAX1722/MAX1723
V
V
OUT
T
A
T
A
T
A
T
A
= +25°C
1.223
1.210
1.235
1.247
1.260
20
V
FB
= 0°C to +85°C
= +25°C
1.5
2.2
0.5
1.0
500
5
Feedback Bias Current
I
FB
MAX1722/MAX1723
nA
= +85°C
N-Channel On-Resistance
P-Channel On-Resistance
N-Channel Switch Current Limit
Switch Maximum On-Time
R
R
V
V
V
forced to 3.3V
forced to 3.3V
forced to 3.3V
1.0
2.0
600
6.5
Ω
Ω
DS(ON)
OUT
OUT
OUT
DS(ON)
I
400
3.5
mA
µs
LIM
t
ON
Synchronous Rectifier Zero-
Crossing Current
V
forced to 3.3V
5
20
35
mA
µA
µA
OUT
Quiescent Current into OUT
Shutdown Current into OUT
(Notes 3, 4)
1.5
0.01
0.1
3.6
0.5
T
A
T
A
T
A
T
A
= +25°C
= +85°C
= +25°C
= +85°C
MAX1723/MAX1724
(Notes 3, 4)
0.001
0.01
0.5
MAX1722/MAX1724
(Note 4)
Quiescent Current into BATT
µA
2
_______________________________________________________________________________________
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
ELECTRICAL CHARACTERISTICS (continued)
(V
= 1.2V, V
= 3.3V (MAX1722/MAX1723), V
= V
(MAX1724), SHDN = OUT, R = ∞, T = 0°C to +85°C,
OUT(NOM) L A
BATT
OUT
OUT
unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBꢀL
CꢀNDITIꢀNS
MIN
TYP
0.001
0.01
400
500
2
MAX
UNITS
T
A
T
A
= +25°C
= +85°C
0.5
Shutdown Current into BATT
MAX1724 (Note 4)
µA
V
IL
MAX1723/MAX1724
MAX1723/MAX1724
75
mV
nA
SHDN Voltage Threshold
SHDN Input Bias Current
V
IH
800
100
T
T
= +25°C
= +85°C
MAX1723/MAX1724,
A
V
= 5.5V
SHDN
7
A
ELECTRICAL CHARACTERISTICS
(V
= 1.2V, V
= 3.3V (MAX1722/MAX1723), V
= V
(MAX1724), SHDN = OUT, R = ∞, T = -40°C to +85°C,
OUT(NOM) L A
BATT
OUT
OUT
unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
2.767
3.075
3.383
5.125
5.5
UNITS
MAX1724EZK27
MAX1724EZK30
MAX1724EZK33
MAX1724EZK50
MAX1722/MAX1723
MAX1722/MAX1723
2.633
2.925
3.218
4.875
2
Output Voltage
V
V
V
OUT
Output Voltage Range
V
V
OUT
Feedback Voltage
V
1.200
1.270
1.0
FB
R
R
N-Channel On-Resistance
P-Channel On-Resistance
N-Channel Switch Current Limit
Switch Maximum On-Time
V
V
V
forced to 3.3V
forced to 3.3V
forced to 3.3V
Ω
DS(ON)
DS(ON)
OUT
OUT
OUT
2.0
Ω
I
400
3.5
620
mA
µs
LIM
t
6.5
ON
Synchronous Rectifier Zero-
Crossing Current
V
forced to 3.3V
5
35
mA
µA
OUT
Quiescent Current into OUT
(Notes 3,4)
3.6
V
MAX1723/MAX1724
MAX1723/MAX1724
75
IL
SHDN Voltage Threshold
mV
V
800
IH
Note 1: Limits are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.
A
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: V
forced to the following conditions to inhibit switching: V
= 1.05
V
(MAX1724), V
= 3.465V
OUT
OUT
OUT
OUT(NOM)
(MAX1722/MAX1723).
_______________________________________________________________________________________
3
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
Typical Operating Characteristics
(Figure 3 (MAX1723), Figure 7 (MAX1722), Figure 8 (MAX1724), V
unless otherwise noted.)
= V = 1.5V, L = 10µH, C = 10µF, C
= 10µF, T = +25°C,
A
BATT
IN
IN
OUT
EFFICIENCY vs. LOAD CURRENT
(V = 5.0V)
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
(V = 3.3V)
(V
= 2.5V)
OUT
OUT
OUT
100
90
100
100
V
IN
= 3.3V
V = 4.0V
IN
V
IN
= 2.5V
V
= 2.0V
IN
V
IN
= 2.0V
90
80
90
80
V
IN
= 2.0V
80
70
60
V = 1.5V
IN
70
60
50
70
60
V
IN
= 1.0V
V
IN
= 1.0V
V
IN
= 1.5V
1
V
IN
= 1.0V
10
L = DO1606
100 1000
V
IN
= 1.5V
1
L = DO1606
100 1000
L = DO1606
100 1000
50
50
0.01
0.1
10
0.01
0.1
1
0.01
0.1
10
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
QUIESCENT CURRENT INTO OUT
vs. OUTPUT VOLTAGE
STARTUP VOLTAGE
vs. LOAD CURRENT
2.0
2.4
200
RESISTIVE LOAD
V = 5.0V
OUT
NO LOAD
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.2
V
= 2.5V
OUT
160
120
80
40
0
2.0
1.8
1.6
1.4
1.2
V
OUT
= 5.0V
V
OUT
= 3.3V
1.0
0.8
0.6
0
1
2
3
4
5
0.01
0.1
1
10
100
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
STARTUP VOLTAGE vs.
TEMPERATURE
SWITCHING WAVEFORMS
1.2
1.0
0.8
0.6
0.4
0.2
NO LOAD
I
LX
500mA/div
V
OUT
50mV/div
V
LX
2V/div
0
1µs/div
-40
-15
10
35
60
85
I
= 50mA, V = 5.0V, V = 3.3V
OUT IN
TEMPERATURE (°C)
OUT
4
_______________________________________________________________________________________
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
Typical Operating Characteristics (continued)
(Figure 3 (MAX1723), Figure 7 (MAX1722), Figure 8 (MAX1724), V
unless otherwise noted.)
= V = 1.5V, L = 10µH, C = 10µF, C
= 10µF, T = +25°C,
OUT A
BATT
IN
IN
SHUTDOWN RESPONSE
LOAD-TRANSIENT RESPONSE
V
5V
OUT
3.3V
2V/div
A
0
50mA
2V
B
V
SHDN
1V/div
0
0
1ms/div
200µs/div
A: V , 50mV/div
OUT
OUT
V
IN
= 3.3V, V
= 5.0V, R
= 100Ω
OUT
OUT
B: I , 20mA/div
SHUTDOWN INPUT THRESHOLD
vs. TEMPERATURE
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
RISING EDGE
FALLING EDGE
-40
-15
10
35
60
85
TEMPERATURE (°C)
Pin Description
PIN
NAME
FUNCTION
Battery Input and Damping Switch Connection
MAX1722
MAX1723
MAX1724
1
—
2
—
1
1
3
2
BATT
SHDN
GND
Shutdown Input. Drive high for normal operation. Drive low for shutdown.
Ground
2
Feedback Input to Set Output Voltage. Use a resistor-divider network to
adjust the output voltage. See Setting the Output Voltage section.
3
4
5
3
4
5
—
4
FB
OUT
LX
Power Output. OUT also provides bootstrap power to the IC.
Internal N-channel MOSFET Switch Drain and P-Channel Synchronous
Rectifier Drain
5
_______________________________________________________________________________________
5
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
OUT
MAX1723
ZERO-
CROSSING
DETECTOR
STARTUP
CIRCUITRY
P
SHDN
FB
CONTROL
LOGIC
DRIVER
LX
ERROR
COMPARATOR
N
CURRENT
LIMIT
1.235V REFERENCE
GND
Figure 1. MAX1723 Simplified Functional Diagram
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 cur-
rent 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.
Detailed Description
The MAX1722/MAX1723/MAX1724 compact, high-effi-
ciency, 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 syn-
chronous rectifier that reduces cost by eliminating the
need for an external diode and improves overall efficien-
cy 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.
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 P-
channel MOSFET turns on and shunts the MOSFET
body diode. As a result, the rectifier voltage drop is sig-
nificantly reduced, improving efficiency without the
addition of external components.
Low-Voltage Startup Circuit
The MAX1722/MAX1723/MAX1724 contain a low-volt-
age startup circuit to control DC-DC operation until the
output voltage exceeds 1.5V (typ). The minimum start-
PFM Control Scheme
A forced discontinuous, current-limited, pulse-frequency-
modulation (PFM) control scheme is a key feature of the
6
_______________________________________________________________________________________
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
DAMPING
SWITCH
BATT
OUT
MAX1724
ZERO-
CROSSING
STARTUP
DETECTOR
CIRCUITRY
R
2
P
SHDN
CONTROL
LOGIC
DRIVER
LX
ERROR
COMPARATOR
N
R
1
CURRENT
LIMIT
1.235V REFERENCE
GND
Figure 2. MAX1724 Simplified Functional Diagram
lacks a BATT pin; therefore, this circuit is powered
through the OUT pin. Adding a Schottky diode in paral-
lel 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.
10µH
1.2V TO V
OUT
D1
10µF
LX
OUT
SHDN
V
= 3.6V
OUT
R2
10µF
2.37MΩ
MAX1723
GND
FB
Shutdown (MAX1723/MAX1724)
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
R1
1.24MΩ
from the battery to the output. V
falls to approxi-
OUT
mately V - 0.6V and LX remains high impedance.
IN
Shutdown can be pulled as high as 6V, regardless of
the voltage at BATT or OUT. For normal operation, con-
nect SHDN to the input.
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
_______________________________________________________________________________________
7
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
V
OUT
V
IN
OUT
P
MAX1722
MAX1724
BATT
PDRV
DAMPING
SWITCH
TIMING
CIRCUIT
DAMP
LX
N
NDRV
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)
BATT/Damping Switch
(MAX1722/MAX1724)
Design Procedure
Setting the Output Voltage
(MAX1722/MAX1723)
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.
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
V
OUT
R2 = R1
−1
FB
where V = 1.235V.
FB
8
_______________________________________________________________________________________
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
For maximum output current, choose the inductor value
so that the controller reaches the current-limit before
the maximum on-time is triggered:
INPUT
0.8V TO V
10µH
OUT
V
t
BATT ON(MAX)
OUTPUT
2V TO 5.5V
L <
10µF
BATT
LX
I
LIM
OUT
where the maximum on-time is typically 5µs, and the
current limit (I
) is typically 500mA (see Electrical
LIM
R2
R1
MAX1722
10µF
Characteristics table).
FB
For larger inductor values, determine the peak inductor
current (I
by:
PEAK)
GND
V
t
BATT ON(MAX)
L
I
=
PEAK
Figure 7. Adjustable Output Circuit
INPUT
Inductor Selection
10µH
0.8V TO V
OUT
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 physi-
cal size for a given series resistance, allowing the
smallest overall circuit dimensions. Circuits using larger
inductance values may start up at lower battery volt-
ages, provide higher efficiency, and exhibit less ripple,
but they may reduce the maximum output current. This
occurs when the inductance is sufficiently large to pre-
C1
10µF
BATT
LX
OUTPUT
OUT (NOM)
OUT
V
MAX1724
C2
10µF
ON
OFF
SHDN
GND
vent the maximum current limit (I
) from being
LIM
reached before the maximum on-time (t
expires.
)
ON(MAX)
Figure 8. MAX1724 Standard Application Circuit
Table 1. Suggested Inductors and
Suppliers
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 effi-
ciency. Table 1 lists suggested inductors and suppliers.
PHONE
MANUFACTURER
Coilcraft
INDUCTOR
WEBSITE
DO1608 Series
DO1606 Series
847-639-2361
www.coilcraft.com
770-436-1300
www.murata.com
Murata
LQH4C Series
Maximum Output Current
The maximum output current depends on the peak induc-
tor current, the input voltage, the output voltage, and the
overall efficiency (η):
CDRH4D18 Series
CR32 Series
CMD4D06 Series
847-545-6700
www.sumida.com
Sumida
Sumitomo/
Daidoo Electronics
+81 (06) 6355-5733
www.daidoo.co.jp
CXLD140 Series
V
V
1
2
BATT
I
=
I
η
OUT(MAX)
PEAK
OUT
3DF Type
D412F Type
847-297-0070
www.toko.com
Toko
_______________________________________________________________________________________
9
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
Table 2. Suggested Surface-Mount Capacitors and Manufacturers (C1 and C2)
CAPACITOR
VALUE
PHONE
WEBSITE
MANUFACTURER
DESCRIPTION
1µF to 10µF
X7R Ceramic
843-448-9411
www.avxcorp.com
AVX
TAJ Tantalum Series
TPS Tantalum Series
10µF to 330µF
1µF to 22µF
10µF to 330µF
68µF to 330µF
X5R/X7R Ceramic
T494 Tantalum Series
T520 Tantalum Series
864-963-6300
www.kemet.com
Kemet
408-749-9714
www.secc.co.jp
Sanyo
33µF to 330µF
33µF to 330µF
1µF to 10µF
TPC Polymer Series
X5R/X7R Ceramic
X7R Ceramic
800-368-2496
www.t-yuden.org
Taiyo Yuden
TDK
847-803-6100
www.tdk.com
594D Tantalum Series
595D Tantalum Series
203-452-5664
www.vishay.com
Vishay Sprague
10µF to 330µF
For most applications, the peak inductor current equals
the current limit. However, for applications using large
inductor values or low input voltages, the maximum on-
time limits the peak inductor current (see Inductor
Selection section).
where I
is the peak inductor current (see Inductor
PEAK
Selection section). For ceramic capacitors, the output
voltage ripple is typically dominated by V
. For
RIPPLE(C)
example, a 10µF ceramic capacitor and a 10µH induc-
tor typically provide 75mV of output ripple when step-
ping up from 3.3V to 5V at 50mA. Low input-to-output
voltage differences (i.e. two cells to 3.3V) require high-
er output capacitor values.
Capacitor Selection
Choose input and output capacitors to supply the input
and output peak currents with acceptable voltage rip-
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.
ple. The input filter capacitor (C ) reduces peak cur-
IN
rents 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.
PC Board Layout Considerations
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 capaci-
tor:
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
(
)
(
)
Chip Information
VRIPPLE ESR ≈ IPEAK RESR COUT
(
)
(
)
TRANSISTOR COUNT: 863
1
2
L
2
2
VRIPPLE C
≈
I
(
-IOUT
)
PEAK
(
)
V
OUT -VBATT C
(
)
OUT
10 ______________________________________________________________________________________
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
Pin Configurations (continued)
TOP VIEW
SHDN
GND
FB
1
2
3
5
4
LX
BATT
GND
1
2
3
5
4
LX
MAX1723
MAX1724
OUT
OUT
SHDN
THIN SOT23-5
THIN SOT23-5
Package Information
______________________________________________________________________________________ 11
1.5µA I , Step-Up DC-DC Converters
Q
in Thin SOT23-5
Package Information (continued)
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
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
相关型号：
MAX17230
2Vâ36V, Synchronous Dual Buck Controller with Integrated Boost and 20μA Quiescent Current
MAXIM
MAX17230ETLR
2Vâ36V, Synchronous Dual Buck Controller with Integrated Boost and 20μA Quiescent Current
MAXIM
MAX17230ETLS
2Vâ36V, Synchronous Dual Buck Controller with Integrated Boost and 20μA Quiescent Current
MAXIM
©2020 ICPDF网 联系我们和版权申明