ADM8843ACPZ-REEL7 Fast Delivery |IC PHOENIX CO.,LIMITED

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ADM8843ACPZ-REEL7
4 White LED Backlight Driver
4 White LED Backlight DriverRev. 0
FEATURES
Drives 4 LEDs from a 2.6 V to 5.5 V (Li-Ion) input supply
1×/1.5×/2× fractional charge pump to maximize
power efficiency
0.3% typical LED current matching
Up to 88% power efficiency over Li-Ion range
Powers main and sub display LEDs with individual shutdown
Package footprint only 9 mm2 (3 mm × 3 mm)
Package height only 0.9 mm
Low power shutdown mode
Shutdown function
Soft-start limiting in-rush current
APPLICATIONS
Cellular phones with main and sub displays
White LED backlighting
Camera flash/strobes and movie light applications
Micro TFT color displays
DSC
PDAs
GENERAL DESCRIPTION
The ADM8843 uses charge pump technology to provide the
power to drive up to four LEDs. The LEDs are used for back-
lighting a color LCD display, having regulated constant current
for uniform brightness intensity. The main display can use up to
three LEDs, and the sub display uses one LED. The CTRL1 and
CTRL2 digital input control pins control the shutdown opera-
tion and the brightness of the main and sub displays.
To maximize power efficiency, the charge pump can operate in
either 1×, 1.5×, or 2× mode. The charge pump automatically
switches between 1×/1.5×/2× modes, based on the input voltage,
to maintain sufficient drive for the LED anodes at the highest
power efficiency.
Improved brightness matching of the LEDs is achieved by a
feedback pin that senses individual LED current with a typical
matching accuracy of 0.3%.
FUNCTIONAL BLOCK DIAGRAM
4.7µF
VCC
1µF
CTRL1
CTRL2
1µF
RSET
ISET
Figure 1.
TABLE OF CONTENTS
Specifications......................................................................................3
Absolute Maximum Ratings.............................................................4
Thermal Characteristics..............................................................4
ESD Caution..................................................................................4
Pin Configuration and Function Descriptions..............................5
Typical Performance Characteristics..............................................6
Theory of Operation.........................................................................9
Automatic Gain Control............................................................10
Brightness Control with a Digital PWM Signal.....................10
LED Brightness Control Using a PWM Signal Applied to
VPWM.............................................................................................12
LED Brightness Control Using a DC Voltage Applied to
VBRIGHT..........................................................................................12
Applications......................................................................................13
Layout Considerations and Noise............................................13
White LED Shorting..................................................................13
Driving Four LEDs in the Main Display Only.......................13
Driving Fewer than Four LEDs................................................13
Using Smaller Capacitor Values...............................................14
Power Efficiency.........................................................................15
Outline Dimensions........................................................................16
Ordering Guide..........................................................................16
REVISION HISTORY
10/04—Revision 0: Initial Version
SPECIFICATIONS
VCC = 2.6 V to 5.5 V; TA = −40°C to +85°C, unless otherwise noted; C1, C2 = 1.0 µF; C3 = 2.2 µF; C4 = 4.7 µF
Table 1.
__ Guaranteed by design. Not 100% production tested.
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 2.
_______
1 Short through LED. Based on long-term current density limitations.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL CHARACTERISTICS
16-Lead LFCSP Package:
θJA = 50°C/W
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
PIN 1
INDICATOR1VOUTC2+ISETGNDC2–CTRL2GNDGND
TOP VIEW
ADM8843
05050-003
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
TYPICAL PERFORMANCE CHARACTERISTICS
10.75
05050-004RSET (kΩ)
D CURRE
NT (mA)
4.756.7512.7514.758.75
Figure 3. ILED (mA) vs. RSET
05050-005TEMPERATURE (°C)
D CURRE
NT (mA)
20.22
Figure 4. ILED (mA) Variation over Temperature (°C), VCC = 3.6 V
05050-006DUTY CYCLE (%)
D CURRE
NT (mA)20601008040
Figure 5. ILED (mA) vs. PWM Dimming (Varying Duty Cycle),
Four LEDs Enabled, Frequency = 1 kHz
4.1
05050-007SUPPLY VOLTAGE (kΩ)
D CURRE
NT (mA)
20.05
Figure 6. ILED (mA) vs. Temperature (°C), Four LEDs Enabled
3.8
05050-008SUPPLY VOLTAGE (V)
D CURRE
NT (mA)
2.63.04.65.43.45.04.2
Figure 7. ILED (mA) vs. Supply Voltage (V)
05050-009DUTY CYCLE (%)
FFICIE
NCY
(%)
04060807050100102030
Figure 8. LED Efficiency vs. Varying Duty Cycle of 1 kHz PWM Signal,
Four LEDs Enabled, 20 mA/LED
180
05050-010SUPPLY VOLTAGE (V)
CURRE
NT (mA)
5.05.4
Figure 9. Supply Current vs. Supply Voltage over Temperature,
Four LEDs Enabled @ 20 mA/LED
VOUT
VCC
Figure 10. 1.5× Mode Operating Waveforms
VOUT
VCC
Figure 11. 1× Mode Operating Waveforms
5050-013WW
VOUT
CTRL1/2
CH3 1.00V
Figure 12. Soft Start Showing the Initial In-Rush Current and VOUT Variation,
Four LEDs @ 20 mA/LED, VCC = 3.6 V
05050-014WW
VOUT
VCC
Figure 13. 2× Mode Operating Waveforms
VCC
R E
FFICIE
NCY70
2.83.03.43.83.63.24.04.22.93.13.33.53.73.94.1
Figure 14. Power Efficiency vs. Supply Voltage over Li-Ion Range,
Four LEDs @ 20 mA/LED
05050-016VCC
R E
FFICIE
NCY70
2.83.03.43.83.63.24.04.22.93.13.33.53.73.94.1
Figure 15. Power Efficiency vs. Supply Voltage over Li-Ion Range,
Four LEDs @ 15 mA/LED
VOUT
CTRL1/2
Figure 16. TPC Delay

Partno	Mfg	Dc	Qty	Available	Descript
ADM8843ACPZ-REEL7 \|ADM8843ACPZREEL7	AD	N/a	13746	avai	4 White LED Backlight Driver