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PDF CAT3648 Data sheet ( Hoja de datos )
| Número de pieza | CAT3648 | |
| Descripción | 4-Channel Ultra High Efficiency Quad-Mode LED Driver | |
| Fabricantes | Catalyst Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de CAT3648 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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CAT3648
4-Channel Ultra High Efficiency Quad-Mode™
LED Driver with 32 Dimming Levels
FEATURES
High efficiency 1.33x charge pump
Quad-mode charge pump: 1x, 1.33x, 1.5x, 2x
Drives up to 4 LEDs at 25mA each
1-wire EZDim™ 32 linear steps
Power efficiency up to 92%
Low noise input ripple in all modes
“Zero” current shutdown mode
Soft start and current limiting
Short circuit protection
Thermal shutdown protection
3mm x 3mm, 16-pad TQFN package
APPLICATION
LCD Display Backlight
Cellular Phones
Digital Still Cameras
Handheld Devices
ORDERING INFORMATION
Part Number
Qty per Reel
CAT3648HV3-GT2
2000 (1)
Marking
JAAN
Notes: (1) NiPdAu Plated Finish (RoHS-compliant)
PIN CONFIGURATION
(Top View)
DESCRIPTION
The CAT3648 is a high efficiency quad-mode
fractional charge pump that can drive up to four LEDs
programmable by a one wire digital interface. The
inclusion of a 1.33x fractional charge pump mode
increases device efficiency by up to 10% over tradi–
tional 1.5x charge pumps with no added external
capacitors.
Low noise input ripple is achieved by operating at a
constant switching frequency which allows the use of
small external ceramic capacitors. The multi-fractional
charge pump supports a wide range of input voltages
from 2.5V to 5.5V.
The EN/DIM logic input functions as a chip enable and
a digital dimming interface for setting the current in all
LED channels. The 1-wire pulse-dimming interface
supports 32 linear steps from full-scale down to zero
current.
The device is available in the tiny 16-pad TQFN
3mm x 3mm package with a max height of 0.8mm.
Catalyst Semiconductor’s Quad-Mode™ 1.33x,
charge pump switching architecture is patented.
TYPICAL APPLICATION CIRCUIT
1µF 1µF
VIN
2.4V CIN
to
5.5V 1µF
1-Wire
EZDimTM
Programming
3.74kΩ
C1+
VIN
C1- C2+
C2-
VOUT
CAT3648
EN/DIM
RSET
GND
LED1
LED2
LED3
LED4
VOUT
COUT
1µF
20mA
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. MD-5031, Rev. A
1 page  
www.DataCShAeetT4U3.c6om48
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 80mA (4 LEDs at 20mA), CIN = COUT = C1 = C2 = 1μF, TAMB = 25°C unless otherwise specified.
Switching Frequency vs. Temperature
1.3
Output Resistance vs. Input Voltage
12
1.2
1.5x Mode
1.1
10 2x
8
1.0
0.9 1.33x, 2x Mode
0.8
6
1.5x
4
2
1x
1.33x
0.7
-40
0 40 80
TEMPERATURE [°C]
120
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE [V]
Power Up in 1x Mode
Power Up in 1.33x Mode
Power Up in 1.5x Mode
Power Up in 2x Mode
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5
Doc. No. MD-5031, Rev. A
5 Page 
Unused LED Channels
For applications not requiring all the channels, it is
recommended the unused LED pins be tied directly to
VOUT (see Figure 4).
1µF 1µF
VIN
CIN
1µF
ENABLE
DIMMING
RSET
C1+
VIN
C1- C2+
C2-
VOUT
CAT3648
EN/DIM
RSET
GND
LED1
LED2
LED3
LED4
COUT
1µF
Figure 4. Application with 3 LEDs
Protection Mode
If an LED is disconnected, the driver senses that and
automatically ignores that channel. When all LEDs are
disconnected, the driver goes to 1x mode where the
output is equal to the input voltage.
www.DataCShAeetT4U3.c6om48
External Components
The driver requires four external 1μF ceramic capa-
citors for decoupling input, output, and for the charge
pump. Both capacitors type X5R and X7R are
recommended for the LED driver application. In all
charge pump modes, the input current ripple is kept
very low by design and an input bypass capacitor of
1μF is sufficient.
In 1x mode, the device operates in linear mode and
does not introduce switching noise back onto the
supply.
Recommended Layout
In charge pump mode, the driver switches internally at
a high frequency. It is recommended to minimize trace
length to all four capacitors. A ground plane should
cover the area under the driver IC as well as the
bypass capacitors. Short connection to ground on
capacitors CIN and COUT can be implemented with the
use of multiple via. A copper area matching the TQFN
exposed pad (TAB) must be connected to the ground
plane underneath. The use of multiple via improves
the package heat dissipation.
As soon as the output exceeds about 6V, the driver
resets itself and re-evaluates the mode.
GND
If the die temperature exceeds +150°C, the driver will
enter a thermal protection shutdown mode. When the
device temperature drops by about 20°C, the device
will resume normal operation.
Pin1
C2
LED Selection
LEDs with forward voltages (VF) ranging from 1.3V to
4.3V may be used. Selecting LEDs with lower VF is
recommended in order to improve the efficiency by
keeping the driver in 1x mode longer as the battery
voltage decreases.
For example, if a white LED with a VF of 3.3V is
selected over one with VF of 3.5V, the driver will stay
in 1x mode for lower supply voltage of 0.2V. This
helps improve the efficiency and extends battery life.
RSET
EN/DIM
GND
COUT
CIN
GND
Figure 5. Recommended Layout
C1
VIN
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
11
Doc. No. MD-5031, Rev. A
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet CAT3648.PDF ] | |
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