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PDF MAX1573 Data sheet ( Hoja de datos )
| Número de pieza | MAX1573 | |
| Descripción | White LED 1x/1.5x Charge Pump | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-2847; Rev 0; 4/03
www.DataSheet4U.com
White LED 1x/1.5x Charge Pump in UCSP
General Description
The MAX1573 fractional charge pump drives up to four
white LEDs with regulated constant current for uniform
intensity. By utilizing proprietary adaptive 1x/1.5x
modes and ultra-low-dropout current regulators, it
maintains the highest possible efficiency over the full
1-cell Li+ battery input voltage range. The 1MHz fixed-
frequency switching allows for tiny external compo-
nents and the regulation scheme is optimized to ensure
low EMI and low input ripple.
An external resistor sets the full-scale LED current, while
two digital inputs control on/off and select amongst three
levels of brightness. A pulse-width modulation (PWM)
signal can also be used to modulate LED brightness,
requiring no additional components.
The MAX1573 is available in the chip-scale package
(UCSP™) (4 x 4 grid) to minimize PC board area.
Applications
Cell Phones, Smart Phones
PDAs, Digital Cameras, Camcorders
MP3 Players
Other Handhelds with Color Displays
Features
o Proprietary Adaptive 1x/1.5x Modes
o High Efficiency (PLEDs/PBATT), Up to 92%
o 2% LED Current Matching and Accuracy
o 28mA/LED Drive Capability
o Low Input Ripple and EMI
o Eliminates Ballast Resistors
o Logic or PWM Dimming Control
o Low 0.1µA Shutdown Current
o 2.7V to 5.5V Input Voltage Range
o Soft-Start Limits Inrush Current
o Output Overvoltage Protection
o Thermal Shutdown Protection
o No External Schottky Diode Required
o Tiny 2.1mm x 2.1mm x 0.6mm UCSP Package
PART
MAX1573EBE-T
Ordering Information
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 14 UCSP (4 x 4)
Typical Operating Circuit
Pin Configuration
1µF 1µF
VIN
2.7V TO 5.5V
1µF
ON/OFF
AND
DIMMING
CONTROL
RSET
C1N C1P C2N C2P
IN OUT
EN1 MAX1573 LED1
EN2 LED2
LED3
SET LED4
GND
1µF
VOUT
UP TO 4 LEDS
TOP VIEW
A
B
C
D
1 234
C1P OUT EN1 EN2
C2N C2P
SET
IN LED4 LED2
C1N GND LED3 LED1
UCSP is a trademark of Maxim Integrated Products, Inc.
UCSP 4 ✕ 4
________________________________________________________________ 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 page  
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White LED 1x/1.5x Charge Pump in UCSP
Block Diagram
C1P C1N
C2P C2N
IN OUT
1x/1.5x REGULATED CHARGE PUMP
EN1
EN2
P
0.15V
BRIGHTNESS
CONTROL
0.6V
P
N
SET
MAX1573
1.25V
MINIMUM
SELECT
LDO CURRENT
REGULATOR
LDO CURRENT
REGULATOR
LDO CURRENT
REGULATOR
LDO CURRENT
REGULATOR
LED1
LED2
LED3
LED4
GND
Detailed Description
The MAX1573 is a complete charge-pump buck-boost
converter requiring only four small ceramic capacitors.
The MAX1573 utilizes a proprietary 1x/1.5x fractional
charge-pump topology to drive up to four white LEDs
with regulated constant current for uniform intensity.
The MAX1573 operates with a 1MHz fixed frequency.
An external resistor (RSET) programs the full-scale LED
current, while two digital inputs control on/off and pro-
vide brightness control.
Output Regulation
The MAX1573 operates in 1x mode until just above
dropout. Then the MAX1573 switches to 1.5x charge-
pump mode to regulate the lowest of LED1–LED4 to
150mV and maintain constant LED brightness even at
very low battery voltages. Using this topology, there is
no LED brightness change during the 1x/1.5x switchover,
which guarantees no flicker on the display. The
switchover scheme has low hysteresis, minimizing
operation in the less-efficient 1.5x mode. The 1x mode
produces almost no ripple, while the 1.5x mode regu-
lates the output voltage by controlling the rate at which
the transfer capacitors are charged. In this way, the
switching frequency remains constant for reduced input
ripple and stable noise spectrum.
Soft-Start
The MAX1573 includes soft-start circuitry to limit inrush
current at turn-on. When starting up with an output
voltage that is not near the input voltage, the output
capacitor is charged directly from the input with a DAC-
ramped current source (with no charge-pump action)
until the output voltage is near the input voltage. Once
this occurs, the charge pump determines if 1x or 1.5x
mode is required. In the case of 1x mode, the soft-start
is terminated and normal operation begins. In the case
of 1.5x mode, soft-start operates until the lowest of
LED1–LED4 reaches regulation. If an overload condi-
tion occurs, soft-start repeats every 2.1ms. If the output
is shorted to ground, the output current is limited by
the MAX1573 fractional-switching technique.
True Shutdown Mode
When EN1 and EN2 are grounded, the MAX1573 is in
shutdown, and the charge pump examines whether the
input voltage is greater than or less than the output volt-
age and shorts the transfer capacitor nodes to either IN
or OUT as necessary. The output is high impedance in
either case.
Thermal Shutdown
The MAX1573 includes a thermal-limit circuit that shuts
down the IC at about +160°C. Turn-on occurs after the
IC cools by approximately 20°C.
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MAX1573.PDF ] | |
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