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Teilenummer | CAT3644 |
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Beschreibung | 4-Channel Ultra High Efficiency LED Driver | |
Hersteller | ON Semiconductor | |
Logo | ||
Gesamt 13 Seiten CAT3644
4-Channel Ultra High
Efficiency LED Driver
Description
The CAT3644 is a high efficiency 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 traditional 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 2.5 V to 5.5 V.
The EN/DIM logic input functions as a chip enable and a digital
dimming interface for current setting of all LEDs. Six different current
ratios are available via the interface.
The device is available in the tiny 16−pad TQFN 3 mm x 3 mm
package with a max height of 0.8 mm.
ON Semiconductor’s 1.33x charge pump switching architecture is
patented.
Features
• High Efficiency 1.33x Charge Pump
• Charge Pump: 1x, 1.33x, 1.5x, 2x
• Drives up to 4 LEDs at 25 mA Each
• 1−wire EZDim LED Current Programming
• 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
• 3 mm x 3 mm, 16−pad TQFN Package
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
Applications
• LCD Display Backlight
• Cellular Phones
• Digital Still Cameras
• Handheld Devices
© Semiconductor Components Industries, LLC, 2014
August, 2014 − Rev. 8
1
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TQFN−16
HV3 SUFFIX
CASE 510AD
PIN CONNECTIONS
LED2
LED3
LED4
RSET
1
C2−
C2+
C1−
C1+
(Top View)
MARKING DIAGRAMS
JAAG
AXXX
YWW
JAAH
AXXX
YWW
JAAG = CAT3644HV3−T2
JAAH = CAT3644HV3−GT2
A = Assembly Location
XXX = Last Three Digits of Assembly Lot Number
Y = Production Year (Last Digit)
WW = Production Week (Two Digits)
ORDERING INFORMATION
Device
CAT3644HV3−T2
(Note 1)
CAT3644HV3−GT2
(Note 2)
Package
TQFN−16
(Pb−Free)
TQFN−16
(Pb−Free)
Shipping†
2000 /
Tape & Reel
1. Matte−Tin Plated Finish (RoHS−compliant).
2. NiPdAu Plated Finish (RoHS−compliant).
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
Publication Order Number:
CAT3644/D
CAT3644
TYPICAL PERFORMANCE CHARACTERISTICS
(VIN = 3.6 V, IOUT = 80 mA (4 LEDs at 20 mA), CIN = COUT = C1 = C2 = 1 mF, TAMB = 25°C unless otherwise specified.)
1.3 12
1.2
1.5x Mode
1.1
10 2x
8
1.0
0.9 1.33x, 2x Mode
6
1.5x
4
1.33x
0.8
0.7
−40
0 40 80
TEMPERATURE (°C)
Figure 9. Switching Frequency vs.
Temperature
120
2 1x
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
Figure 10. Output Resistance vs. Input Voltage
Figure 11. Power Up in 1x Mode
Figure 12. Power Up in 1.33x Mode
Figure 13. Power Up in 1.5x Mode
Figure 14. Power Up in 2x Mode
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6
6 Page CAT3644
Unused LED Channels
For applications not requiring all the channels, it is
recommended the unused LED pins be tied directly to VOUT
(see Figure 27).
1 mF 1 mF
VIN
CIN
1 mF
ENABLE
DIMMING
RSET
C1+ C1− C2+ C2−
VIN VOUT
CAT3644
EN/DIM
LED1
LED2
RSET
GND
LED3
LED4
COUT
1 mF
Figure 27. 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.
As soon as the output exceeds about 6 V, 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.
LED Selection
LEDs with forward voltages (VF) ranging from 1.3 V to
4.3 V 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 3.3 V is selected
over one with VF of 3.5 V, the driver will stay in 1x mode for
lower supply voltage of 0.2 V. This helps improve the
efficiency and extends battery life.
External Components
The driver requires four external 1 mF ceramic capacitors
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 1 mF 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.
GND
Pin1
C2
RSET
GND
EN/DIM
COUT
CIN
GND
Figure 28. Recommended Layout
C1
VIN
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12
12 Page | ||
Seiten | Gesamt 13 Seiten | |
PDF Download | [ CAT3644 Schematic.PDF ] |
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