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CAT3643 Schematic ( PDF Datasheet ) - Catalyst Semiconductor

Teilenummer CAT3643
Beschreibung 3-Channel Ultra High Efficiency Quad-Mode TM LED Driver
Hersteller Catalyst Semiconductor
Logo Catalyst Semiconductor Logo 




Gesamt 17 Seiten
CAT3643 Datasheet, Funktion
CAT3643
3-Channel Ultra High Efficiency Quad-Mode™
LED Driver
FEATURES
DESCRIPTION
„ High efficiency 1.33x charge pump
„ Quad-mode charge pump: 1x, 1.33x, 1.5x, 2x
„ Drives up to 3 LEDs at 32mA each
„ 1-wire EZDim™ LED current programming
„ Power efficiency up to 92%
„ Low noise input ripple in all modes
The CAT3643 is a high efficiency quad-mode
fractional charge pump that can drive up to three
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
traditional 1.5x charge pumps with no added external
capacitors.
„ “Zero” current shutdown mode
„ Soft start and current limiting
„ Short circuit protection
„ Thermal shutdown protection
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 2.4V to 5.5V.
„ Tiny 12-lead XQFN, 12-lead TDFN and 16-lead
TQFN packages
The EN/DIM logic input functions as a chip enable and
a digital dimming interface for current setting of all
APPLICATION
LEDs. Six different current ratios are available via the
interface.
„ LCD Display Backlight
www.DataSheet4U.com
„ Cellular Phones
„ Digital Still Cameras
The device is available in the tiny 12-lead XQFN 2.5 x
2.5mm with max height of 0.4mm or in 16-lead TQFN
or 12-lead TDFN 3mm x 3mm package with a max
„ Handheld Devices
height of 0.8mm.
ORDERING INFORMATION
Part
Package
Number
Package
Marking
CAT3643HV2-T2 TDFN-12 3 x 3mm(1) HABF
CAT3643HV3-T2 TQFN-16 3 x 3mm(1) JAAE
CAT3643HL1-T2 XQFN-12 2.5 x 2.5mm(1) LB
Notes:
(1) Matte-Tin Plated Finish (RoHS-compliant)
(2) Quantity per reel is 2000
For Ordering Information details, see page 16.
The 1.33x charge pump architecture with two fly
capacitors is patent pending.
TYPICAL APPLICATION CIRCUIT
1µF 1µF
VIN
2.4V
to
5.5V
CIN
1µF
1-Wire
EZDimTM
Programming
3.8k
C1+
VIN
C1- C2+
C2-
VOUT
White LEDs
CAT3643
EN/DIM
RSET
GND
LED1
LED2
LED3
VOUT
COUT
1µF
20mA
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. 5022, Rev. B






CAT3643 Datasheet, Funktion
CAT3643
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 60mA (3 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
0.8
0.7
-40
1.33x, 2x Mode
0 40 80
TEMPERATURE [°C]
120
6
1.5x
4
1.33x
2 1x
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
Doc. No. 5022, Rev. B
6 © 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice

6 Page









CAT3643 pdf, datenblatt
CAT3643
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
CAT3643
EN/DIM
RSET
GND
LED1
LED2
LED3
COUT
1µF
Figure 4. Application with 2 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.
As soon as the output exceeds about 6V, the driver
resets itself and reevaluate the mode.
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.
External Components
The driver requires four external 1μF ceramic capaci–
tors 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.
Pin1
C2
RSET
EN/DIM
C1
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.
GND
COUT
VOUT
GND
CIN
Figure 5. TDFN-12 Recommended Layout
VIN
Doc. No. 5022 Rev. B
12 © 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice

12 Page





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