MAX1835EUT [MAXIM]
Switching Regulator, 1A, BICMOS, PDSO6, MO-178AB, SOT-23, 6 PIN;型号: | MAX1835EUT |
厂家: | MAXIM INTEGRATED PRODUCTS |
描述: | Switching Regulator, 1A, BICMOS, PDSO6, MO-178AB, SOT-23, 6 PIN 信息通信管理 开关 光电二极管 |
文件: | 总10页 (文件大小:222K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
19-1802; Rev 0; 10/00
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
General Description
Features
The MAX1832–MAX1835 are high-efficiency step-up
converters with complete reverse battery protection that
protects the device and the load when the battery is
reversed. They feature a built-in synchronous rectifier,
which allows for over 90% efficiency and reduces size
and cost by eliminating the need for an external
Schottky diode.
♦ Reverse Battery Protection for DC-DC Converter
and Load
♦ Up to 90% Efficiency
♦ No External Diode or FETs Needed
♦ Internal Synchronous Rectifier
♦ 4µA Quiescent Current
These step-up converters operate from a +1.5V to
+5.5V input voltage range and deliver up to 150mA of
load current. The MAX1833/MAX1835 have a fixed
+3.3V output, and the MAX1832/MAX1834 have
adjustable outputs from +2V to +5.5V. In shutdown, the
MAX1832/MAX1833 connect the battery input to the
voltage output, allowing the input battery to be used as
a backup or real-time clock supply when the converter
is off (see Selector Guide).
♦ <1µA Shutdown Supply Current
♦ +1.5V to +5.5V Input Voltage Range
♦ Accurate SHDN Threshold for Low-Battery Cutoff
♦ BATT Connected to OUT in Shutdown for Backup
Power (MAX1832/MAX1833)
♦ RST Output (MAX1833/MAX1835)
The MAX1832–MAX1835 are available in a miniature 6-
pin SOT23 package. The MAX1832EVKIT is available to
shorten the design cycle.
♦ Fixed +3.3V Output Voltage (MAX1833/MAX1835)
♦ Adjustable Output Voltage (MAX1832/MAX1834)
♦ Up to 150mA Output Current
♦ Tiny 6-Pin SOT23 Package
________________________Applications
Ordering Information
Medical Diagnostic Equipment
Pagers
PIN-
PACKAGE
TOP
MARK
PART
TEMP. RANGE
Hand-Held Instruments
Remote Wireless Transmitters
Digital Cameras
Cordless Phones
Battery Backup
MAX1832EUT-T
MAX1833EUT-T
MAX1834EUT-T
MAX1835EUT-T
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
AAOT
AAOU
AAOV
AAOW
Note: Requires special solder temperature profile described in
the Absolute Maximum Ratings.
PC Cards
Local 3.3V or 5V Supply
Pin Configurations
Selector Guide
OUTPUT
VOLTAGE
OUTPUT VOLTAGE
IN SHUTDOWN
TOP VIEW
PART
MAX1832EUT-T
MAX1833EUT-T
MAX1834EUT-T
MAX1835EUT-T
Adjustable
Fixed 3.3V
Adjustable
Fixed 3.3V
V
V
BATT
BATT
SHDN
BATT
GND
1
2
3
6
5
4
FB
SHDN
1
2
3
6
5
4
RST
OUT
LX
MAX1832
MAX1834
MAX1833
MAX1835
V
V
- 0.7V
- 0.7V
BATT
BATT
OUT BATT
LX
GND
SOT23-6
SOT23-6
________________________________________________________________ Maxim Integrated Products
1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
ABSOLUTE MAXIMUM RATINGS
BATT, LX to GND.........................................................-6V to +6V
LX to OUT....................................................................-6V to +1V
SHDN to GND..............................................-6V to (V
OUT, FB, RST TO GND ............................................-0.3V to +6V
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) (Note 2) ...................+300°C
+ 0.3V)
OUT
LX Current................................................................................1A
Continuous Power Dissipation (T = +70°C)
A
SOT23-6 (derate 9.1mW/°C above +70°C) (Note 1)....727mW
Note 1: Thermal properties are specified with product mounted on PC board with one square-inch of copper area and still air.
Note 2: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during solder attach and rework. This limit permits only the use of the solder profiles recommended in
the industry-standard specification, IPC/JEDEC J-STD-020A, paragraph 7.6, Table 3 for the IR/VPR and Convection reflow.
Preheating is required. Hand or wave soldering is not allowed.
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
= +1.5V, V
= +3.3V, V = +2V, GND = 0, T = -40°C to +85°C. Typical values are at T = +25°C, unless otherwise
BATT A A
SHDN
OUT
noted.) (Note 3)
PARAMETER
Output Range
SYMBOL
CONDITIONS
MAX1832/MAX1834
MIN
2.0
TYP
MAX
5.5
UNITS
V
V
V
OUT
Battery Input Range
V
1.5
5.5
BATT
T = +25°C
1.22
1.24
1.5
A
Startup Battery Input Voltage
V
R
= 2.6kΩ
V
V
V
SU
LOAD
T
= -40°C to +85°C
A
T = +25°C
A
3.225
3.208
1.208
1.204
3.290
3.355
3.372
1.248
1.252
20
MAX1833/
MAX1835
Output Voltage
FB Trip Voltage
V
OUT
T
= -40°C to +85°C
A
T = +25°C
A
1.228
MAX1832/
MAX1834
V
FB
T
= -40°C to +85°C
A
MAX1832/
MAX1834,
T = +25°C
A
3.5
4.0
0.4
FB Input Bias Current
I
nA
FB
T = -40°C to +85°C
A
V
= +1.3V
FB
T = +25°C
A
1.2
1.5
1.3
1.6
V
= +3.3V
= 100mA
OUT
N-Channel On-Resistance
P-Channel On-Resistance
P-Channel Catch-Diode Voltage
R
R
Ω
Ω
V
NCH
I
LX
T = -40°C to +85°C
A
T = +25°C
A
0.5
V
= +3.3V
= 100mA
OUT
PCH
I
LX
T = -40°C to +85°C
A
I
LX
= 100mA, PCH off, V
= +3.5V,
OUT
0.73
525
V
V
= +1.3V
FB
T = +25°C
A
435
400
3.5
2
615
650
6.5
34
N-Channel Switch Current Limit
Switch Maximum On-Time
I
= +3.3V
mA
µs
MAX
OUT
T
A
= -40°C to +85°C
t
5
ON
T = +25°C
A
17
Synchronous Rectifier Zero-
Crossing Current
V
= +3.3V
= +3.5V,
mA
OUT
OUT
T
A
= -40°C to +85°C
0
39
T = +25°C
A
2.5
7.0
8.0
1
Quiescent Current into OUT
(Note 4)
V
V
µA
µA
= +1.3V
FB
T = -40°C to +85°C
A
Shutdown Current into OUT
V
= +3.5V, V
= V = 0V
0.05
OUT
SHDN
FB
2
_______________________________________________________________________________________
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
ELECTRICAL CHARACTERISTICS (continued)
(V
= +1.5V, V
= +3.3V, V = +2V, GND = 0, T = -40°C to +85°C. Typical values are at T = +25°C, unless otherwise
BATT A A
SHDN
OUT
noted.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
= V = V = -3V
MIN
TYP
0
MAX
UNITS
Reverse Battery Current into
OUT
V
= 0, V
10
µA
OUT
OUT
BATT
SHDN
LX
T = +25°C
A
1.8
5.0
6.0
1
V
V
= +3.5V,
= +1.3V
Quiescent Current into BATT
Shutdown Current into BATT
µA
µA
µA
V
FB
T = -40°C to +85°C
A
V
V
V
= +3.5V, V
= +2V, V = 0
SHDN
0.001
0.002
OUT
BATT
Reverse Battery Current into
BATT
= 0, V
= V = V = -3V
SHDN LX
10
OUT
BATT
SHDN Logic Low
= +1.5V to +5.5V
0.3
BATT
T = +25°C
1.185
1.170
1.228
1.271
1.286
A
A
SHDN Threshold
Rising edge
V
T
= -40°C to +85°C
SHDN Threshold Hysteresis
SHDN Input Bias Current
0.02
13
V
V
V
= +5.5V, V
= +5.5V, T = +25°C
100
150
nA
µA
OUT
OUT
SHDN
A
SHDN Reverse Battery Current
= 0, V
= V
= V = -3V
52
BATT
SHDN
LX
MAX1833/
MAX1835,
falling edge
T = +25°C
2.830
2.800
2.980
3.110
3.140
A
RST Threshold
V
T
= -40°C to +85°C
A
RST Voltage Low
I
= 1mA, V
= +2.5V
OUT
0.2
V
RST
T = +25°C
0.1
1
100
A
RST Leakage Current
V
V
= +5.5V
nA
RST
T = -40°C to +85°C
A
T = +25°C
A
1
100
10
LX Leakage Current
= +5.5V
nA
LX
T = -40°C to +85°C
A
100
0.001
150
90
LX Reverse Battery Current
Maximum Load Current
Efficiency
V
V
V
= 0, V
= V
= V = -3V
µA
mA
%
OUT
BATT
SHDN
LX
I
= +2V, V
= +2V, V
= +3.3V
LOAD
BATT
BATT
OUT
OUT
= +3.3V, I
= 40mA
LOAD
Note 3: All units are 100% production tested at T =+25°C. Limits over the operating temperature range are guaranteed by design
A
and not production tested.
Note 4: Supply current into OUT. This current correlates directly to the actual battery-supply current, but is reduced in value accord-
ing to the step-up ratio and efficiency.
_______________________________________________________________________________________
3
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
Typical Operating Characteristics
(V
= +3.3V, V
= +2V, unless otherwise noted.) (Figure 1)
OUT
BATT
EFFICIENCY vs. LOAD CURRENT
(V = 5.0V)
EFFICIENCY vs. LOAD CURRENT
(V = 3.3V)
EFFICIENCY vs. LOAD CURRENT
(V = 2.5V)
OUT
OUT
OUT
95
90
85
80
75
70
65
95
90
85
80
75
85
80
V = +2.0V
BATT
V
= +3.3V
BATT
V
= +2.7V
BATT
V
= +2.0V
BATT
V
= +2.7V
BATT
V
= +1.5V
BATT
V
= V
BATT
SHDN
R1 = 100kΩ
V
= +1.5V
BATT
75
70
V
= V
BATT
SHDN
R2 = 100kΩ
R1 = 309Ω
R2 = 100kΩ
MAX1834
V
= +1.5V
BATT
C
C
= 20µF
= 20µF
IN
OUT
V
= V
BATT
SHDN
MAX1835
MAX1834
0.1
1
10
(mA)
100
1000
0.1
1
10
(mA)
100
1000
0.1
1
10
10
100
I
I
LOAD
LOAD
I
(mA)
LOAD
INPUT CURRENT AND OUTPUT VOLTAGE
vs. BATTERY VOLTAGE (SHUTDOWN, NO LOAD)
MAXIMUM OUTPUT CURRENT
vs. BATTERY VOLTAGE
STARTUP BATTERY VOLTAGE
vs. LOAD RESISTANCE
MAX1832/35 toc06
1.7
1.6
1.5
1.4
1.3
1.2
1.0
0.8
0.6
0.4
0.2
0
250
200
150
100
50
6
5
4
V
= V
BATT
V
R
= 0
SHDN
SHDN
LOAD
= ∞
V
= +2.5V
OUT
MAX1833
V
= +3.3V
= +5.0V
OUT
V
OUT
V
= +5.0V
3
2
1
OUT
V
OUT
I
BATT
V
= +3.3V
OUT
0
V
= +2.5V
OUT
-1
0
-0.2
1.2
1
2
3
4
5
6
10
100
1k
10k
-6 -5 -4 -3 -2 -1
V
0
1
(V)
2
3
4
5
6
V
(V)
R
LOAD
(Ω)
BATT
BATT
INPUT CURRENT AND OUTPUT VOLTAGE
vs. BATTERY VOLTAGE (SHUTDOWN, LOADED)
INPUT CURRENT AND OUTPUT VOLTAGE
INPUT CURRENT AND OUTPUT VOLTAGE
vs. BATTERY VOLTAGE (ON, NO LOAD)
vs. BATTERY VOLTAGE (ON, LOADED)
MAX1832/35 toc07
MAX1832/35 toc08
MAX1832/35 toc09
300
160
300
250
200
150
100
50
6
5
4
4.0
3.5
3.0
6
5
4
V
R
= V
V
R
= 0
SHDN
LOAD
BATT
= ∞
V
V
R
= V
SHDN
SHDN
LOAD
BATT
= 3.3V
= 22Ω
140
120
100
80
OUT
250
200
150
100
50
R3 = 1MΩ
MAX1833
= 22Ω
LOAD
R4 = 220kΩ
C1 = 10nF
R3 = 1MΩ
R4 = 220kΩ
C1 = 10nF
I
BATT
2.5
2.0
1.5
V
OUT
I
BATT
3
2
1
3
2
1
V
OUT
V
OUT
60
I
BATT
1.0
0.5
0
40
20
I
0
0
BATT
4
0
0
0
-1
-1
-0.5
-50
-20
-50
-6 -5 -4 -3 -2 -1
V
0
1
(V)
2
3
4
5
6
-6 -5 -4 -3 -2 -1
V
0
1
2
3
5
6
-6 -5 -4 -3 -2 -1
V
0
1
2
3
4
5
6
(V)
(V)
BATT
BATT
BATT
4
_______________________________________________________________________________________
High-Efficiency Step-Up Converters with
Reverse Battery Protection in a SOT23-6
Typical Operating Characteristics (continued)
(V
= +3.3V, V
= +2V, unless otherwise noted.) (Figure 1)
OUT
BATT
ON/OFF RESPONSE
LOAD TRANSIENT
MAX1832/35 toc10
MAX1832/35 toc11
V
V
BATT
1V/div
OUT
100mV/div
V
I
OUT
1V/div
LOAD
100mA/div
0
2ms/div
40µs/div
V
OUT
= V
= 2.0V, R
= 22Ω,
R
V
= 22Ω TO 200Ω,
SHDN
BATT
LOAD
V
= 3.3V
= +2.0V
BATT
SHUTDOWN RESPONSE
LINE TRANSIENT
MAX1832/35 toc13
MAX1832/35 toc12
V
V
SHDN
1V/div
BATT
500mV/div
0
V
OUT
1V/div
V
OUT
50mV/div
0
MAX1833
40µs/div
40µs/div
= +3.3V,
R
LOAD
= 22Ω, V
= 3.3V, V
= 2.0V
I
= 100mA, V
BATT
BATT
BATT
OUT
V
OUT
= +2.0V TO +2.5V
SWITCHING WAVEFORMS
MAX1832/35 toc14
V
LX
500mA/div
V
OUT
100mV/div
V
LX
2V/div
10µs/div
= +3.3V, V
I
= 40mA, V
= +2.0V
OUT
OUT
BATT
_______________________________________________________________________________________
5
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
Pin Description
PIN
NAME
FUNCTION
MAX1832
MAX1834
MAX1833
MAX1835
Shutdown. A high logic level turns on the device. When SHD N is low the part is off,
and the current into BATT is typically 0.1µA. For the MAX1832/MAX1833, the
battery is connected to OUT through an internal PFET and the external inductor
when SHD N is low. SHD N can be used for low-battery cutoff (1.228V threshold).
See Low-Battery Cutoff. SHD N has reverse battery protection.
1
1
SHDN
2
3
2
3
BATT
GND
Battery Voltage Connection. BATT has reverse battery protection.
Ground
Inductor Connection. N-channel MOSFET switch drain and synchronous
rectifier P-channel switch drain. LX has reverse battery protection.
4
5
4
5
LX
OUT
FB
Output Voltage. Bootstrapped supply for the device. Output sense point for
MAX1833/MAX1835.
MAX1832/MAX1834 Feedback Input. Set the output voltage through a
resistor-divider network. See Setting the Output Voltage.
6
—
6
MAX1833/MAX1835 Power-On Reset Open-Drain Output. RST pulls low when
the output is 10% below the regulation point. If not used, connect to GND.
—
RST
+1.5V TO +3.3V
BATTERY
+1.5V TO +5.0V
BATTERY
10µF
10µH
10µF
10µH
BATT
OUTPUT
+3.3V
BATT
OUTPUT
+5.0V
LX
OUT
RST
LX
OUT
FB
10µF
R4
220kΩ
100kΩ
R4
220kΩ
R2
MAX1833
MAX1835
MAX1832
MAX1834
309kΩ
POWER-ON
RESET
SHDN
SHDN
C1
10nF
C1
R3
1MΩ
R3
1MΩ
10nF
R1
100kΩ
GND
GND
Figure 1b. MAX1832/MAX1834 Typical Operating Circuit
Figure 1a. MAX1833/MAX1835 Typical Operating Circuit
6
_______________________________________________________________________________________
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
reverse battery protection N-channel MOSFET opens,
Detailed Description
protecting the device and load (Figures 2 and 3).
The MAX1832–MAX1835 compact, high-efficiency
Previously, this level of protection required additional
circuitry and reduced efficiency due to added compo-
nents in the battery current path.
step-up converters feature 4µA quiescent supply cur-
rent to ensure the highest possible efficiency over a
wide load range. With a minimum +1.5V input voltage,
these devices are well suited for applications with two
alkaline cells, two nickel-metal-hydride (NiMH) cells, or
one lithium ion (Li+) cell. For the MAX1832 and
MAX1833, the battery is connected to OUT through the
inductor and an internal PFET when SHDN is low. This
allows the input battery to be used as a backup or real-
time clock supply when the converter is off by eliminat-
ing the voltage drop across the PFET body diode.
Applications Information
Shutdown
When SHDN is low, the device is off and no current is
drawn from the battery. When SHDN is high, the device
is on. If SHDN is driven from a logic-level output, the
logic high (on) level should be referenced to VOUT to
avoid intermittent turn on. If SHDN is not used at all,
connect it to OUT. With SHDN connected to OUT, the
MAX1834/MAX1835 startup voltage (1.65V) is slightly
higher, due to the voltage across the PFET body diode.
The SHDN pin has reverse battery protection.
The MAX1832–MAX1835 are ideal for low-power appli-
cations where ultra-small size is critical. These devices
feature built-in synchronous rectification that signifi-
cantly improves efficiency and reduces size and cost
by eliminating the need for an external Schottky diode.
Furthermore, these devices are the industry’s first boost
regulators to offer complete reverse battery protection.
This proprietary design protects the battery, IC, and the
circuitry powered by the IC in the event the input bat-
teries are connected backwards.
In shutdown, the MAX1832/MAX1833 connect the bat-
tery input to the output through the inductor and the
internal synchronous rectifier PFET. This allows the
input battery (rather than a separate backup battery) to
provide backup power for devices such as an idled
microcontroller, SRAM, or real-time clock, without the
usual diode forward drop. If the output has a residual
voltage during shutdown, a small amount of energy will
be transfered from the output back to the input immedi-
ately after shutdown. This energy transfer may cause a
slight momemntary “bump” in the input voltage. The
magnitude and duration of the input bump are related
to the ratio of CIN and COUT and the ability of the input
to sink current. With battery input sources, the bump
will be negligible, but with power-supply inputs (that
typically cannot sink current), the bump may be 100s of
mV.
Control Scheme
A current-limited control scheme is a key feature of the
MAX1832–MAX1835. This scheme provides ultra-low
quiescent current and high efficiency over a wide out-
put 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.
In shutdown, the MAX1834/MAX1835 do not turn on the
internal PFET and thus do not have an output-to-input
current path in shutdown. This allows a separate back-
up battery, such as a Li+ cell, to be diode-connected at
the output, without leakage current flowing to the input.
The MAX1834/MAX1835 still have the typical input-to-
output current path from the battery to the output,
through the PFET body diode, in shutdown.
An internal synchronous rectifier eliminates the need for
an external Schottky diode 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 significantly
reduced, improving efficiency without adding external
components.
Reverse Battery Protection
The MAX1832–MAX1835 have a unique proprietary
design that protects the battery, IC, and circuitry pow-
ered by the IC in the event that the input batteries are
connected backwards. When the batteries are connect-
ed correctly, the reverse battery protection N-channel
MOSFET is on and the device operates normally.
When the batteries are connected backwards, the
Low-Battery Cutoff
The SHDN trip threshold of the MAX1832–MAX1835
can be used as a voltage detector, with a resistor-
divider, to power down the IC when the battery voltage
falls to a set level (Figure 1). The SHDN trip threshold is
1.228V. To use a resistor-divider to set the shutdown
voltage, select a value for R3 in the 100kΩ to 1MΩ
_______________________________________________________________________________________
7
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
OUT
ZERO-
CROSSING
DETECTOR
MAX1832
MAX1834
STARTUP
CIRCUITRY
P
SHDN
FB
CONTROL
LOGIC
LX
DRIVER
N
ERROR
COMPARATOR
BATT
REVERSE BATTERY
PROTECTION MOSFET
N
CURRENT
LIMIT
1.228V
GND
Figure 2. MAX1832/MAX1834 Simplified Functional Diagram
OUT
ZERO-
CROSSING
DETECTOR
MAX1833
MAX1835
STARTUP
CIRCUITRY
P
CONTROL
LOGIC
LX
DRIVER
ERROR
COMPARATOR
N
1.228V
BATT
REVERSE BATTERY
PROTECTION MOSFET
N
RST
CURRENT
LIMIT
RESET
N
GND
1.1V
SHDN
Figure 3. MAX1833/MAX1835 Simplified Functional Diagram
8
_______________________________________________________________________________________
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
range to minimize battery drain. Calcuate R4 as follows:
Table 1. Suggested Inductors and
Suppliers
✕
R4 = R3 (V
/ V
- 1)
OFF
SHDN
V
is the battery voltage at which the part will shut
OFF
down and V
MANUFACTURER
INDUCTOR
PHONE
= 1.228V. Note that input ripple can
SHDN
sometimes cause false shutdowns. To minimize the effect
of ripple, connect a low-value capacitor (C1) from SHDN
to GND to filter out input noise. Select a C1 value such
DS1608C-103
DO1606T-103
Coilcraft
847-639-6400
✕
CDRH4D18-100
CR43-100
that the R4 C1 time constant is above 2ms.
Sumida
Murata
847-956-0666
814-237-1431
Power-On Reset
The MAX1833/MAX1835 provide a power-on reset out-
put (RST). A 100kΩ to 1MΩ pullup resistor from RST to
OUT provides a logic control signal. This open-drain
output pulls low when the output is 10% below its regu-
lation point. If not used, connect it to GND.
LQH4N100K
Table 2. Suggested Surface-Mount
Capacitors and Manufacturers
Setting the Output Voltage
The output voltage of the MAX1832/MAX1834 is
adjustable from +2V to +5.5V, using external resistors
R1 and R2 (Figure 1b). Since FB leakage is 20nA
(max), select feedback resistor R1 to be 100kΩ to
1MΩ. Calculate R2 as follows:
VALUE
(µF)
MANU-
FACTURER
DESCRIPTION
PHONE
594/595 D-
series tantalum
Sprague
AVX
603-224-1961
803-946-0690
847-390-4373
408-573-4150
4.7 to
47
TAJ, TPS-
series tantalum
V
V
OUT
R2 = R1
−1
4.7 to
10
FB
X7R ceramic
X7R ceramic
TDK
where V = 1.228V.
FB
4.7 to
22
Taiyo Yuden
Inductor Selection
The control scheme of the MAX1832–MAX1835 permits
flexibility in choosing an inductor. A 10µH inductor per-
forms well for most applications, but values from 4.7µH
to 100µH may also be used. Small inductance values
typically offer smaller physical size. Large inductance
values minimize output ripple but reduce output power.
Output power is reduced when the inductance is large
enough to prevent the maximum current limit (525mA)
from being reached before the maximum on-time (5µs)
expires.
Capacitor Selection
Choose an output capacitor to achieve the desired out-
put ripple percentage.
2
0.5 × L × 0.525A
C
>
OUT
2
r% × V
OUT
where r is the desired output ripple in %. A 10µF ceramic
capacitor is a good starting value. The input capacitor
reduces the peak current drawn from the battery and
can be the same value as the input capacitor. A larger
input capacitor can be used to further reduce ripple and
improve efficiency.
For maximum output current, choose L such that:
V
1µs
(
V
5µs
)
(
)
BATT(MAX)
BATT(MIN)
< L <
0.525A
0.525A
0.525A
PC Board Layout and Grounding
Careful printed circuit layout is important for minimizing
ground bounce and noise. Keep the IC’s GND pin and
the ground leads of the input and output filter capaci-
tors less than 0.2in (5mm) apart. In addition, keep all
connections to the FB and LX pins as short as possible.
In particular, when using external feedback resistors,
V
−
R
(
+R
)
BATT(MIN)
NCH IND
2
0.525A
I
×
OUT(MAX) =
V
OUT
2
where R
is the R
is the inductor series resistance, and R
NCH
IND
of the N-channel MOSFET (0.4Ω typ).
DS(ON)
_______________________________________________________________________________________
9
High-Efficiency Step-Up Converters with
Reverse Battery Protection in SOT23-6
Package Information
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 10
© 2000 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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