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PDF MAX1524 Data sheet ( Hoja de datos )

Número de pieza MAX1524
Descripción Simple SOT23 Boost Controllers
Fabricantes Maxim Integrated 
Logotipo Maxim Integrated Logotipo



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No Preview Available ! MAX1524 Hoja de datos, Descripción, Manual

19-1926; Rev 0; 2/01
EVAALVUAAILTAIOBNLEKIT
Simple SOT23 Boost Controllers
General Description
The MAX1522/MAX1523/MAX1524 are simple, compact
boost controllers designed for a wide range of DC-DC
conversion topologies, including step-up, SEPIC, and
flyback applications. They are for applications where
extremely low cost and small size are top priorities.
These devices are designed specifically to provide a
simple application circuit and minimize the size and
number of external components, making them ideal for
PDAs, digital cameras, and other low-cost consumer
electronics applications.
These devices use a unique fixed on-time, minimum off-
time architecture, which provides excellent efficiency
over a wide-range of input/output voltage combinations
and load currents. The fixed on-time is pin selectable to
either 0.5µs (50% max duty cycle) or 3µs (85% max
duty cycle), permitting optimization of external compo-
nent size and ease of design for a wide range of output
voltages.
The MAX1522/MAX1523 operate from a +2.5V to +5.5V
input voltage range and are capable of generating a
wide range of outputs. The MAX1524 is intended for
bootstrapped operation, permitting startup with lower
input voltage. All devices have internal soft-start and
short-circuit protection to prevent excessive switching
current during startup and under output fault condi-
tions. The MAX1522/MAX1524 have a latched fault
mode, which shuts down the controller when a short-
circuit event occurs, whereas the MAX1523 reenters
soft-start mode during output fault conditions. The
MAX1522/MAX1523/MAX1524 are available in a space-
saving 6-pin SOT23 package.
________________________Applications
Low-Cost, High-Current,
or High-Voltage Boost
Conversion
LCD Bias Supplies
Industrial +24V and +28V
Power Supplies
Low-Cost, Multi-Output
Flyback Converters
SEPIC Converters
Low-Cost Battery-
Powered Applications
Pin Configurations
TOP VIEW
GND 1
6 VCC
FB 2
MAX1522
MAX1523
MAX1524
5 EXT
SET 3
4 SHDN
____________________________Features
o Simple, Flexible Application Circuit
o 2-Cell NiMH or Alkaline Operation (MAX1524)
o Low Quiescent Current (25µA typ)
o Output Fault Protection and Soft-Start
o High Efficiency Over 1000:1 IOUT Range
o Pin-Selectable Maximum Duty Factor
o Micropower Shutdown Mode
o Small 6-Pin SOT23 Package
o No Current-Sense Resistor
Ordering Information
PART
TEMP. RANGE
MAX1522EUT-T
MAX1523EUT-T
MAX1524EUT-T
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
TOP
MARK
AAOX
AAOY
AAOZ
__________Typical Operating Circuit
INPUT
VCC
6 VCC
5
EXT
50% 85%
OFF ON
MAX1522
3 SET MAX1523 FB 2
MAX1524
4 SHDN
GND 1
N
OUTPUT
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.

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MAX1524 pdf
Simple SOT23 Boost Controllers
Pin Description
PIN NAME
FUNCTION
1
GND
Ground
2 FB Feedback Input. Connect FB to external resistive voltage-divider. FB regulates to 1.25V.
On-Time Control. Connect SET to VCC to set the fixed 3µs on-time (85% duty cycle). Connect SET to
3 SET GND to set the fixed 0.5µs on-time (50% duty cycle). See On-Time SET Input section for more
information.
4
SHDN
Shutdown Control Input. Drive SHDN high for normal operation. Drive SHDN low for low-power
shutdown mode. Driving SHDN low clears the fault latch of the MAX1522 and MAX1524.
5
EXT
External MOSFET Drive. EXT drives the gate of an external NMOS power FET and swings from VCC
to GND.
Supply Voltage to the IC. Bypass VCC to GND with a 0.1µF capacitor. Connect VCC to a +2.5V to
6
VCC
+5.5V supply, which may come from VIN (nonbootstrapped) or VOUT (bootstrapped) or from the
output of another regulator. For bootstrapped operation, connect VCC to the output through a series
10resistor.
Detailed Description
The MAX1522/MAX1523/MAX1524 are simple, com-
pact boost controllers designed for a wide range of
DC-DC conversion topologies including step-up,
SEPIC, and flyback applications. These devices are
designed specifically to provide a simple application
circuit with a minimum of external components and are
ideal for PDAs, digital cameras, and other low-cost
consumer electronics applications.
These devices use a unique fixed on-time, minimum
off-time architecture, which provides excellent efficien-
cy over a wide range of input/output voltage combina-
tions and load currents. The fixed on-time is pin
selectable to either 0.5µs or 3µs, permitting optimiza-
tion of external component size and ease of design for
a wide range of output voltages.
Control Scheme
The MAX1522/MAX1523/MAX1524 feature a unique
fixed on-time, minimum off-time architecture, which pro-
vides excellent efficiency over a wide range of
input/output voltage combinations. The fixed on-time is
pin selectable to either 0.5µs or 3µs for a maximum
duty factor of either 45% or 80%, respectively. An
inductor charging cycle is initiated by driving EXT high,
turning on the external MOSFET. The MOSFET remains
on for the fixed on-time, after which EXT turns off the
MOSFET. EXT stays low for at least the minimum off-
time, and another cycle begins when FB drops below
its 1.25V regulation point.
Bootstrapped vs. Nonbootstrapped
The VCC supply voltage range of the MAX1522/
MAX1523/MAX1524 is +2.5V to +5.5V. The supply for
VCC can come from the input voltage (nonboot-
strapped), the output voltage (bootstrapped), or an
independent regulator.
The MAX1522/MAX1523 are usually utilized in a non-
bootstrapped configuration, allowing for high or low
output voltage operation. However, when both the input
and output voltages fall within the +2.5V to +5.5V
range, the MAX1522/MAX1523 may be operated in
nonbootstrapped or bootstrapped mode. Bootstrapped
mode provides higher gate-drive voltage to the MOS-
FET switch, reducing I2R losses in the switch, but will
also increase the VCC supply current to charge and
discharge the gate. Depending upon the MOSFET
selected, there may be minor variation in efficiency vs.
load vs. input voltage when comparing bootstrapped
and nonbootstrapped configurations.
The MAX1524 is always utilized in bootstrapped config-
uration for applications where the input voltage range
extends down below 2.5V and the output voltage is
between 2.5V and 5.5V. VCC is connected to the output
(through a 10series resistor) and receives startup
voltage through the DC current path from the input
through the inductor, diode, and 10resistor. The
MAX1524 features a low-voltage startup oscillator that
_______________________________________________________________________________________ 5

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MAX1524 arduino
Simple SOT23 Boost Controllers
Diode Selection
The MAX1522/MAX1523/MAX1524shigh switching fre-
quency demands a high-speed rectifier. Schottky
diodes are recommended for most applications
because of their fast recovery time and low forward
voltage. Ensure that the diodes current rating is ade-
quate to withstand the diodes RMS current:
IDIODE(RMS) < IOUT × IPEAK
Also, the diode reverse breakdown voltage must
exceed VOUT. For high output voltages (50V or above),
Schottky diodes may not be practical because of this
voltage requirement. In these cases, use a high-speed
silicon rectifier with adequate reverse voltage. Another
consideration for high input voltages is reverse leakage
of the diode. This should be considered using the man-
ufacturers specification due to its direct influence on
system efficiency.
Layout Considerations
High switching frequencies and large peak currents
make PC board layout a very important part of design.
Good design minimizes excessive EMI on the feedback
paths and voltage gradients in the ground plane, both
of which can result in instability or regulation errors.
Connect the inductor, input filter capacitor, and output
filter capacitor as close together as possible, and keep
their traces short, direct, and wide. Connect their
ground pins at a single common node in a star-ground
configuration. The external voltage-feedback network
should be very close to the FB pin, within 0.2in (5mm).
Keep noisy traces (such as the trace from the junction
of the inductor and MOSFET) away from the voltage-
feedback network; also keep them separate, using
grounded copper. The MAX1522/MAX1523/ MAX1524
evaluation kit manual shows an example PC board lay-
out and routing scheme.
Generating Resistance
with PC Board Traces
If the output capacitors ESR is too low for proper regu-
lation, it can be increased artificially directly on the PC
board. For example, an additional 50mof ESR added
to the output capacitor provides best regulation. The
resistivity of a 10mil trace using 1oz copper is about
50mper inch. Therefore, a 10mil trace 1in long gener-
ates the required resistance.
______________________________________________________________________________________ 11

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