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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Features and Benefits
Proprietary adaptive control scheme (1x, 1.5x, 2x) 0.5% typical LED current matching 2 separate serial interfaces for dimming control Drives up to 6 white LEDs (4 display backlight, 2 flash/torch) 30 mA per LED channel for display backlight 100 mA per LED channel for flash/torch backlight 320 mA total output current capability Low EMI design and soft-start function Short circuit, overvoltage, thermal shutdown protection 0.75 mm very thin profile, 3 mm x 3 mm package
Description
The A8530 high efficiency charge pump ICs offer a simple, low-cost white LED driver solution for driving four display backlight and two flash/torch/video mode white LEDs. Using a proprietary control scheme (1x, 1.5x, and 2x), the A8530 can deliver well-matched LED current while maintaining the highest efficiency and low EMI. The LED current is regulated over the entire range of Li+ battery voltage to provide uniform intensity. LED brightness and on/off can be controlled for 4 display backlight LEDs and 2 flash/torch LEDs through 2 single-wire serial interface pins. The A8530 is available in a very thin profile (0.75 mm nominal height) 3 mmx 3 mm QFN/MLP 16 pin package. Applications include: White LED backlights for cellular phones, PDAs Digital cameras, camcorders Other portable device white LED backlighting 320 mA WLED flash/torch
Package: 16 pin QFN/MLP (suffix ES)
Approximate Scale 1:1
Typical Applications
VBATT 2.7 to 5.5 V CIN 4.7 F C1 1 F C2 1 F VIN C1+ C1- VOUT LED1 D1 D2 D3 D4 D5 D6 RSET On/Off and Dimming Control C2 1 F COUT 4.7 F VBATT 2.7 to 5.5 V CIN 4.7 F C1 1 F VIN C1+ C1- VOUT LED1 D1 COUT 4.7 F
LED2 C2+ A8530 LED3 C2- LED4 ISET ENM ENF GND LED5 LED6
LED2 C2+ A8530 LED3 C2- LED4 ISET ENM ENF GND LED5 LED6
RSET On/Off and Dimming Control
D5 D6
D1-D4 Backlight; D5-D6 Flash
D1-D4 Backlight; D5-D6 Flash
Figure 1. 4 x 30 mA backlight with 2 x 100 mA flash
VBATT 2.7 to 5.5 V CIN 4.7 F C1 1 F C2 1 F COUT 4.7 F D1 VBATT
Figure 2. 3 x 100 mA flash
VIN C1+ C1-
VOUT LED1
VIN CIN 1 F C1+ C1-
VOUT LED1 D1 D2 D3 D4 D5 D6
LED2 C2+ A8530 LED3 C2- LED4 ISET ENM ENF GND LED5 LED6 RSET On/Off and Dimming Control
LED2 C2+ A8530 LED3 C2- LED4 ISET ENM ENF GND LED5 LED6
RSET On/Off and Dimming Control
D1-D4 Main; D5-D6 Flash VIN>Vf(max)+0.2 V, Vf = LED forward drop
Figure 3. 320 mA flash 8530-DS
Figure 4. High efficiency current sink
A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Functional Block Diagram
C1 1 F C1+ C1 - C2+ C2 1 F C2-
VIN
Fractional Charge Pump (1x, 1.5x, and 2x)
+ -
VOUT
CIN 4.7 F ENM Control, Clock, and Reference
COUT 4.7 F
ENF
Minimum Select LED1 LED2 LED3
Current Mirror
LED4 LED5 IREF IREF LED6
+ -
ISET
+ - + - + - + - + - + -
RSET
GND
Absolute Maximum Ratings
Input or Output Voltage VIN, VOUT, C1+, C1- , C2+, C2- to GND ..................... -0.3 to 6 V All other pins..................................................... -0.3 to VIN + 0.3 V VOUT Short Circuit to GND ....................................................Continuous Operating Ambient Temperature, TA ..................................... -40C to 85C Junction Temperature, TJ(max).............................................................. 150C Storage Temperature, TS ................................................... -55C to 150C
Package Thermal Characteristics Package Thermal Resistance, RJA = 68 C/W (vendor data, on 4-layer PCB; unverified) Device package is lead (Pb) free, with 100% matte tin leadframe plating.
Use the following complete part number when ordering:
Part Number A8530EESTR-T Packaging* 7-in. reel, 1500 pieces/reel Package Type ES, 3 x 3 mm MLP-16
*Contact Allegro for additional packing options.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Pin-out Diagram
ES Package
16 C1+
15 C2-
C2+ VOUT ISET ENF
1 2 3 4 5 6 7 8 EP
13 C1- 12 GND 11 LED1 10 LED2 9 LED3 LED4
ENM
LED6
(Top View)
Terminal List Table
Name C1- C1+ C2- C2+ ENF ENM EP GND ISET LED1, LED2, LED3, and LED4 LED5 and LED6 VIN VOUT Number 13 16 15 1 4 5 - 12 3 8, 9, 10, and 11 6 and 7 14 2 Function Negative terminal of capacitor C1. Connect capacitor C1 between C1+ and C1-. Positive terminal of capacitor C1. Negative terminal of capacitor C2 Positive terminal of capacitor C2. Connect capacitor C2 between C2+ and C2-. Enable and dimming control input for flash/torch. Enable and dimming control input for display backlight. Exposed metal pad on bottom side. Connect this to ground plane for better thermal performance. Ground. Connect RSET resistor to ground to set desired constant current through backlight LEDs. ILED(max) = 220 x 0.6 V / RSET Current sink for display backlight LEDs. If not used, connect to VOUT, but do not leave open. If left open, the IC works in 2 x mode. Current sink for flash/torch LEDs. If not used, connect to VOUT, but do not leave open. If left open, the IC works in 2 x mode. Power supply voltage input. Charge pump output voltage source for display backlight and flash/torch LED anodes. Connect a 4.7 F capacitor, COUT, between VOUT and GND (see figures 1 through 4).
LED5
14 VIN
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
ELECTRICAL CHARACTERISTICSa VIN = ENM = 3.6 V, ENF = GND, C1 = C2 = 1 F, CIN = COUT = 4.7 F, RSET = 6.49 k, TA = -40C to +85C; typical values are at TA = 25C; unless otherwise noted
Characteristics Input Voltage Range Undervoltage Lockout Threshold UVLO Hysteresis Window Quiescent Current Soft-start Completion Time ISET Bias Voltage ISET Leakage in Shutdown ISET Current Range ISET to LEDx Current Ratio for LED1 through LED4 100% Output Current for LED5 and LED6 ILED Accuracy for LED1 through LED4b LED Current Matching for LED1 through LED4c LED Current Matching for LED5 and LED6c Regulation Voltage at LEDx (1.5 x and 2 x modes) 1x mode to 1.5x or 1.5x to 2x mode transition voltage at LEDx Transition-Dropout Deltad Open Loop Output Resistancee LED Leakage in Shutdown Oscillator Frequency Output Overvoltage Protection (guaranteed by design) ENF and ENM Input High Threshold ENF and ENM Input Low Threshold Input High Current Input Low Current ENM and ENF Pulse Low Time (figure 6) ENM and ENF Pulse High Time (figure 6) ENM and ENF Initial Pulse High Time (figure 6) Shutdown or Dimming Reset Delay Thermal Shutdown Threshold
aSpecifications
Symbol VIN VUVLO VUVLOHYS IQ tss VISETBIAS VISETLKG ISET ILEDx/IISET ILED56MAX ILED14 ILED56 VREG Vtrans Vdr ROUT VLEDLKG fosc Vovp VIH VIL IIH IIL tLO tHI tINIHI tSHDN TTSD VIN falling
Test Conditions
Min. 2.7 2.25 - - - - - - 40 - 92 - - - - - - - - - - -
Typ. Max. Units - 5.5 V 2.45 60 6 0.1 2.0 0.6 0.01 - 220 100 1.6 0.5 0.5 250 150 40 1 2.5 5 0.01 1 - - - - - - - - 0.5 165 2.60 - - 2 - - 1 140 - 108 - - - - - - - - - 1 - 6.0 - 0.4 1 1 250 - - - - V mV mA A ms V A A A/A mA % % % mV mV mV A MHz V V V A A s s s ms
oC
Switching in 1.5 x or 2.0 x mode; TA = 25C ENF = ENM = GND; TA = 25C
100% setting, ISET = 60 A Default 100% setting when ENF is enabled ENF = GND, ENM = VIN ENF = VIN, ENM = GND, 100% ENF = ENM = VIN VLEDx falling Measured as Vtrans - Vdropout 1x mode (VIN - VOUT) / IOUT 1.5x mode (1.5 x VIN - VOUT) / IOUT 2x mode (2 x VIN - VOUT) / IOUT ENF = ENM = GND, VIN = 5.5 V Open circuit at any LED that is programmed to be in the ON state Input high logic threshold Input low logic threshold VIH=VIN VIL= GND
EILED14ERR ENF = GND, ENM = VIN
- 1.4 - - - 0.5 0.5
First ENM or ENF pulse after shutdown Falling edge of ENF and/or ENM 20oC hysteresis
50 - -
for the range TA = -40C to 85C are guaranteed by design. bI LED accuracy is defined as ( ISET x 220 - ILEDAVG ) / (ISET x 220). cLED current matching is defined as (I LEDx - ILEDAVG) / ILEDAVG . dDropout voltage V dropout is defined as LEDx-to-GND voltage at which ILEDx drops 10% below the value of ILEDx when VLEDx = 300 mV. eThe open loop output resistance, R OUT, for 1.5 x mode is measured when one of the LEDx pins is tied to ground or open (thus its voltage than 80 mV).
is always less
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Tests performed using application circuit shown in figure 1 TA = 25C, VIN = 3.6 V (unless otherwise noted)
Performance Characteristics
Efficiency versus Supply Voltage
for LED1 through LED4, in parallel
95 90 85 80 95 90 85
Efficiency versus Supply Voltage
for LED5 and LED6, in parallel
VFx = 3.7 V IFx = 100 mA
Eff (%)
75 70 65 60 55 2.7 3.1 3.5 3.9 VIN (V) 4.3
Eff (%)
VFx = 3.4 V IFx = 20 mA
80 75 70
VFx = 3.1 V IFx = 10 mA
65 60 55 4.7 5.1 5.5 2.7 3.1 3.5 3.9 VIN (V) 4.3
VFx = 3.2 V IFx = 50 mA
4.7 5.1 5.5
Logic Level
1.2 1.1 1.0 ILED / Channel (mA) 35 30
RSET versus ILED
VHI
25 20 15 10 5 0
RSET = 6. RSET =
V ENx (V)
0.9 0.8 0.7 0.6 0.5
2.7 3.1 3.5 3.9 VIN (V) 4.3 4.7 5.1 5.5
VLO
4
6
8
10 RSET (
12
14
16
Dimming on ENM
Enable Pulses versus Total Current, LED1 through LED4
VENM
C1 ILED14
Symbol C1 C2 t
Parameter VENM ILED14 time
Units/Division 0.5 V 50 mA 50 ms
C2
t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Tests performed using application circuit shown in figure 1 TA = 25C, VIN = 3.6 V (unless otherwise noted)
Performance Characteristics
LED5-6 ON, 1.5x mode
VIN = 3.2 V, IOUT = 200 mA, VF = 3.1 V
C3 VOUT
Symbol C3 C4 t
Parameter Units/Division 20 mV VOUT Ripple IIN Ripple 50 mA time 500 ns
IIN
C4
t
LED5-6 ON, 2x mode
VIN = 2.7 V, IOUT = 200 mA, VF = 3.1 V
C3
VOUT
Symbol C3 C4 t
Parameter Units/Division VOUT Ripple 20 mV 50 mA IIN Ripple time 500 ns
IIN C4
t
LED1-4 ON, 1.5x mode
VIN = 3.6 V, IOUT = 80 mA, VF = 3.4 V
C3 VOUT VOUT
Symbol C3 C4 t
Parameter Units/Division VOUT Ripple 20 mV IIN Ripple 50 mA time 500 ns
IIN C4
t
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Tests performed using application circuit shown in figure 1 TA = 25C
Performance Characteristics
Turn ON LED1-6 in 1X Mode
VIN = 4.0 V, IOUT = 280 mA
VENF and VENM
Turn ON LED1-6 in 2X mode
VIN = 2.7 V, IOUT = 280 mA
VENF and VENM
C1
VOUT
C1
VOUT
C2
IOUT
IOUT C2
C3
C3
t
t
Symbol C1 C2 C3 t
Parameter Units/Division VENF and VENM 2.00 V 2.00 V VOUT IOUT 100 mA time 0.5 ms
Symbol C1 C2 C3 t
Parameter Units/Division VENF and VENM 2.00 V 2.00 V VOUT IOUT 100 mA time 0.5 ms
Turn ON LED1-6 in 1.5X Mode
VIN = 3.0 V, IOUT = 280 mA
VENF and VENM VOUT
C1
IOUT
C2
C3
t
Symbol C1 C2 C3 t
Parameter Units/Division VENF and VENM 2.00 V 2.00 V VOUT IOUT 100 mA time 0.5 ms
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Application Information
Setting LED Current Use the following formula to set the display backlight LED full current (100%) using RSET on LED1 through LED4. The maximum current through one LED should not exceed 30 mA: RSET = 0.6 V x 220 / ILEDx where RSET is in and ILEDx in amperes. The default flash/torch current on LED5 and LED6 is set internally to 100 mA per channel. When both the display backlight and the flash/torch LEDs are on, the maximum current output from LED1 through LED4 is 30 mA per channel. The output current of the flash/torch LEDs (LED5 and LED6) can be adjusted by serial dimming at the ENF pin within 1 ms after ENF is pulled high. Transitions Between 1x and 1.5x or 2x Modes The A8530 adaptively selects operating mode. When VIN is sufficiently high to maintain VLEDx > 150 mV, the A8350 operates
95 90 85
in 1 x mode unless, as VIN drops, the LEDx nodes fall below the 150 mV threshold. When VLEDx falls below 150 mV, the IC enters 1.5x mode. When the A8530 switches from 1x to 2x mode, it first switches to 1.5x mode for a typical duration of 1 ms before entering 2x mode. When operating in 1.5x mode, if VOUT < VIN, then the IC switches back to 1x mode every 130 ms, and then reenters 1.5x mode again if necessary. Transitions Between 1.5x and 2x Modes The transition from 1.5x to 2x mode depends upon dropout conditions. When operating in 2x mode, the IC switches back to 1.5x mode every 130 ms, and then reenters 2x mode again if necessary. Furthermore, when in 2x mode, whenever a channel disabling is sensed (that is, whenever ENM is held low for > 0.5 ms with ENF high, or vice versa), the IC automatically reverts to 1.5x mode, and then reenters 2x mode again if necessary. Dimming Display Backlight LED1 through LED4 Dimming The display backlight LEDs (LED1 through LED4) brightness and on/off can be controlled using digital input at the ENM pin. The ENM pin accepts one-wire serial pulse input to enable the A8350 and to set up to 11 dimming levels, from 100% down to 5%. When ENM is initially pulled up from shutdown, after a softstart, the current for the backlight LEDs is programmed to 100% of the setting current, which is determined by the current through the ISET pin. Each subsequent pulse reduces the LED current by 10%, and the 10th pulse reduces the current by 5%. The next pulse restores 100% (full) brightness. Figure 6 shows the timing diagram for ENM control.
6 7 8 9 10 11
VIN Falling
80
Eff (%)
70 65 60 55 2.7 3.1 3.5
3.9 VIN (V)
VIN Rising
75
VFx = 3.4 V IFx = 20 mA
4.3
4.7
5.1
5.5
Figure 5. Mode change transitions
tHI(Init)
ENM (LED1-4) or ENF (LED5-6)
0
1
2
3
4
5
tSS IILED(1-4) or IILED(5-6) SHDN 100% 90% 80% 70%
t LO
t HI 100% 90%
tSHDN
60%
50%
40%
30% 20%
10%
5%
SHDN or Dimming Reset
Figure 6. Single-Wire Serial Dimming Control; at pins ENF and ENM.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Flash/Torch LED5 and LED6 Operation The flash/torch LEDs (LED5 and LED6) brightness and on/off can be controlled using digital input at ENF pin. ENF accepts one-wire serial pulse input to enable the A8530 and to set up to 11 dimming levels, from 100 mA (the default 100% level) down to 5 mA. When the ENF pin is initially pulled up from shutdown, after a soft-start (if the IC is not yet soft-started using the ENM pin), the current for LED5 and LED6 is, by default, programmed to 100 mA, corresponding to 100% of flash/torch brightness. Each subsequent pulse reduces the LED current by 10 mA, and the 10th pulse reduces the current by 5 mA. The next pulse then restores to 100 mA (full) output current per channel. Figure 6 shows the timing diagram for ENF. Absolute Level Operation Some applications require dimming to a specific level, regardless of the present level of dimming. For example, if the IC should dim to 30%, this can be done with 7 steps, as shown in figure 6, irrespective of the dimming level in effect. This can be achieved by pulling corresponding ENx
pin low for time greater than tSHDN and then applying pulses as shown in figure 6 (7 for 30% dimming). If the pulses are applied within 2 to 3 ms, the display flicker is not visible. The procedure is shown in figure 7. Shutdown When the ENM pin is pulled low for 0.5 ms or longer, the display backlight channels are shut off and dimming is reset to 100% upon the next ENM going high edge. When the ENF pin is pulled low for 0.5 ms or longer, the brightness of the flash/torch channels is reset to 100 mA upon the next ENF going high edge. When both ENM and ENF are pulled low for 0.5 ms or longer, the A8530 enters the shutdown mode. Short Circuit Protection The A8530 is protected against short circuits on the output. When VOUT is externally pulled below 1.2 V, the IC enters Short Circuit mode. The A8530 resumes normal operation when the short circuit is removed.
Rapid pulse pattern t > tSHDN C1 ENx pulled low VENM
Symbol C1 C2 C3 t
Parameter VENM VOUT IOUT time
Units/Division 2.00 V 2.00 V 50 mA 0.5 ms
C2 VOUT
100% C3 ISET counter resets 30% IOUT
t
Figure 7. Absolute Dimming Level Setting. With ENM pulled low longer the tSHDN, pulsing the corresponding ENx pin sets an absolute target level.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Overvoltage Protection The A8530 is protected up to 4.9 V supply voltage, against accidental overvoltage caused by an open LED. When any LED opens, VOUT will increase till 6 V. Remaining LEDs will continue to function normally. Normal operation will be resumed when the fault is removed. LED Disconnection Every LEDx pin has a disable subcircuit, as shown in figure 8. The A8530 compares the voltage on each LED pin, and if the voltage on the pin is greater than either VOUT - 0.4 V or VIN - 0.4 V, then the corresponding LED pin is disabled.
Thermal Shutdown The IC is internally protected against overtemperature. The overtemperature limit is set to 165C nominal. The IC shuts down when the junction temperature exceeds 165C and automatically turns on again when the IC cools. Component Selection Ceramic capacitors with X5R or X7R dielectric are recommended for the input capacitor, CIN, the output capacitor, COUT, and the charge pump capacitors, C1 and C2.
A8530 VBATT CIN VIN 1x, 1.5x, 2x Charge Pump VOUT COUT
LED Disable Block One of six blocks
- + - +
VOUT - 0.4 Current Sink VIN - 0.4 LED1 D1 D2 D3 D4 D5 D6
Figure 8. LED disable subcircuit. Subcircuit for one LEDx pin shown. A similar block is connected to each LEDx pin.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8530
Ultracompact 6-Channel Backlight and Flash/Torch White LED Driver
Package ES, 3 x 3 mm 16-Pin QFN/MLP
3.15 .124 2.85 .112 16 Preliminary dimensions, for reference only (reference JEDEC MO-220WEED-4) Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area B Exposed thermal pad (reference only, terminal #1 identifier appearance at supplier discretion) C Reference land pattern layout (reference IPC7351 QFN50P300X300X80-17W4M); adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) 16X 0.08 [.003] C 16X 0.30 .012 0.18 .007 0.10 [.004] M C A B 0.05 [.002] M C 0.50 .020 0.30 .012 NOM 0.90 .035 NOM C 1 12X 0.20 .008 MIN 1.70 .067 NOM 0.50 .020 0.30 .012 3.10 .122 NOM 2 1 B 16 0.50 .020 NOM 1.70 .067 NOM 1 2
A B
A 3.15 .124 2.85 .112
SEATING PLANE 0.80 .031 0.70 .028 0.20 .008 REF 0.05 .002 0.00 .000
C
1.70 NOM
.067
4X 0.20 .008 MIN 1.70 .067 NOM 3.10 .122 NOM
16 4X 0.20 .008 MIN 0.23 x 0.23 .009 x .009 REF
The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detailed specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. Copyright(c)2005, 2006 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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