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EL7513
Data Sheet July 2003 FN7112.2
White LED Step-Up Regulator
The EL7513 is a constant current boost regulator specially designed for driving white LEDs. It can drive 4 LEDs in series or up to 12 LEDs in parallel/series configuration and achieves efficiency up to 91%. The brightness of the LEDs is adjusted through a voltage level on the CNTL pin. When the level falls below 0.1V, the chip goes into shut-down mode and consumes less than 1A of supply current for VIN less than 5.5V. The EL7513 is available in the 8-pin TSOT and 8-pin MSOP packages. The TSOT package is just 1mm high, compared to 1.45mm for the standard SOT23 package.
Features
* 2.6V to 13.2V input voltage * 18V maximum output voltage * Drives up to 12 LEDs * 1MHz switching frequency * Up to 91% efficiency * 1A maximum shut-down current * Dimming control * 8-pin TSOT and 8-pin MSOP packages
Applications
* PDAs * Cellular phones
Ordering Information
PART NUMBER EL7513IWT EL7513IWT-T7 EL7513IWT-T13 EL7513IY EL7513IY-T7 EL7513IY-T13 PACKAGE 8-Pin TSOT 8-Pin TSOT 8-Pin TSOT 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP TAPE & REEL 7" 13" 7" 13" PKG. DWG. # MDP0049 MDP0049 MDP0049 MDP0043 MDP0043 MDP0043
* Digital cameras * White LED backlighting
Pinouts
EL7513 (8-PIN TSOT) TOP VIEW
COMP 1 CNTL 2 VOUT 3 LX 4 8 VIN 7 CS 6 SGND 5 PGND
Typical Connection
2.6V TO 5.5V C1 4.7F L 33H D C2 1F
VIN
LX
VOUT CS VCTRL C3 CNTL COMP PGND SGND R1 5
EL7513 (8-PIN MSOP) TOP VIEW
CS 1 VIN 2 PGND 3 SGND 4 8 CNTL 7 COMP 6 LX 5 VOUT
0.1F
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2003. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc. All other trademarks mentioned are the property of their respective owners.
EL7513
Absolute Maximum Ratings (TA = 25C)
COMP, CNTL, CS to SGND. . . . . . . . . . . . . . . . . . . . . . -0.3V to +6V VIN to SGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+14V VOUT to SGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+19V LX to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+20V SGND to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65C to +150C Ambient Operating Temperature . . . . . . . . . . . . . . . .-40C to +85C
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. This part is ESD sensitive. Handle with care. IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typ values are for information purposes only. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER VIN IQ1 IQ1 ICOMP VCOMP ICNTL VCNTL1 VCNTL2
VIN = 3V, VO = 12V, C1 = 4.7F, L = 33H, C 2 = 1F, C3 = 0.1F, R1 = 5, TA = 25C, Unless Otherwise Specified DESCRIPTION CONDITIONS MIN 2.6 VCNTL = 0V VCNTL = 1V, load disconnected COMP connected to SGND 0.5 CNTL = 0V 240 100 VCNTL = 1V VOUT rising VOUT falling, with resistive load 14 17 15 500 0.7 VCNTL = 0V, VLX = 12V 800 VCNTL = 2V, IS = 0 85 1000 90 1 VIN = 2.6V - 5.5V 0.03 1 1200 15 18 16 16 19 17.5 1 11 1.5 TYP MAX 13.2 1 1.5 20 2.5 1 UNIT V A mA A V A mV mV mA V V mA A kHz % A %/V
Input Voltage Total Input Current at Shut-down Quiescent Supply Current at VO Pin COMP Pin Pull-up Current COMP Voltage Swing CNTL Shut-down Current Chip Enable Voltage Chip Disable Voltage
IOUT_ACCURACY VCNTL = 1V VOUT1 VOUT2 ILX RDS_ON ILEAK FS DMAX ICS IO/VIN Over-voltage Threshold Over-voltage Threshold MOSFET Current Limit MOSFET On-resistance MOSFET Leakage Current Switching Frequency Maximum Duty Ratio CS Input Bias Current Line Regulation
Pin Descriptions
8-PIN TSOT 8-PIN MSOP 1 2 3 4 5 6 7 8 7 8 5 6 3 4 1 2 PIN NAME COMP CNTL VOUT LX PGND SGND CS VIN DESCRIPTION Compensation pin. A compensation cap (4700pF to 1F) is normally connected between this pin and SGND. Control pin for dimming and shut-down. A voltage between 250mV and 5.5V controls the brightness, and less than 100mV shuts down the converter. Output voltage sense. Use for over voltage protection. Inductor connection pin. The drain of internal MOSFET. Power Ground pin. The source of internal MOSFET. Signal Ground. Ground pin for internal control circuitry. Needs to connect to PGND at only one point. Current sense pin. Connect to sensing resistor to set the LED bias current. Power supply for internal control circuitry.
2
EL7513 Block Diagram
2.6V TO 5.5V CIN 4.7F REFERENCE GENERATOR 1MHz OSCILLATOR THERMAL SHUTDOWN OVER-VOLTAGE PROTECTION VOUT LX PWM LOGIC I(LED) COUT 1F L 33H
VIN
COMP CCOMP 0.1F
+ + + BOOST I-SENSE START-UP CONTROL
PGND CS 5
PWM SIGNAL 617K 50K
ERROR AMP + -
VCNTL
CNTL
SGND
Typical Performance Curves
All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
1.05 1.04 1.03 1.02 1.01 1 2.5 3.5 3 2.5 FS (MHz) IIN (A) 2 1.5 1 0.5 3 3.5 4 VIN (V) 4.5 5 5.5 0 2.5 4.5 6.5 8.5 VIN (V) 10.5 12.5 14.5
VCNTL=0V, 0.1V WHITE LEDs DISCONNECTED
FIGURE 1. SWITCHING FREQUENCY vs VIN
FIGURE 2. QUIESCENT CURRENT
3
EL7513 Typical Performance Curves (Continued) All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
VCNTL=1V 35 30 25 ILED (mA) 20 15 10 5 0 0 0.5 1 1.5 2 2.5 ILED (mA) 16 15.8 15.6 15.4 15.2 15 14.8 14.6 14.4 14.2 14 2.5 3 3.5 4 VIN (V) 4.5 5 5.5
VCNTL (V)
FIGURE 3. ILED vs VCNTL
FIGURE 4. ILED vs VIN
L VIN 4.7F 33H
BAT54HT1 2 LEDs IN A SERIES VIN=4.2V EFFICIENCY (%)
1F
90
8
VIN
LX
4
85 VIN=2.7V 80
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5
75 L=COILCRAFT LPO1704-333CM 5 10 15 20 25 30
70
IO (mA)
FIGURE 5A. 2 LEDs IN A SERIES
FIGURE 5.
FIGURE 5B. EFFICIENCY vs IO
VIN 4.7F
L 33H
BAT54HT1 3 LEDs IN A SERIES 90
1F
EFFICIENCY (%)
8
VIN
LX
4
85
VIN=4.2V VIN=2.7V
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5
80
75 L=COILCRAFT LPO1704-333CM 5 10 15 20 25 30
70
IO (mA)
FIGURE 6A. 3 LEDs IN A SERIES
FIGURE 6.
FIGURE 6B. EFFICIENCY vs IO
4
EL7513 Typical Performance Curves (Continued) All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
L VIN 4.7F 33H 1F 90 VIN=4.2V EFFICIENCY (%) 8 VIN LX 4 85 VIN=3.3V VIN=2.7V BAT54HT1 4 LEDs IN A SERIES
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5
80
75 L=COILCRAFT LPO1704-333CM 5 10 15 20 25 30
70
LED CURRENT (mA)
FIGURE 7A. 4 LEDs IN A SERIES
FIGURE 7.
FIGURE 7B. EFFICIENCY vs IO
L VIN 4.7F 33H
BAT54HT1 2 LEGS OF 2 LEDs IN A SERIES VIN=4.2V
1F
90
VIN
LX
EFFICIENCY (%)
8
4
85 VIN=2.7V 80
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5
75 L=COILCRAFT LPO1704-333CM 20 30 40 50 60
70 10
IO (mA)
FIGURE 8A. 2 LEGS OF 2 LEDs IN A SERIES
FIGURE 8.
FIGURE 8B. EFFICIENCY vs IO
L VIN 4.7F 33H
BAT54HT1 2 LEGS OF 3 LEDs IN A SERIES 1F 90 VIN=4.2V
VIN
LX
EFFICIENCY (%)
8
4
85 VIN=2.7V 80
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5
75 L=SUMIDA CMD13D13-33H 20 30 40 50 60
70 10
IO (mA)
FIGURE 9A. 2 LEGS OF 3 LEDs IN A SERIES
FIGURE 9.
FIGURE 9B. EFFICIENCY vs IO
5
EL7513 Typical Performance Curves (Continued) All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
L VIN 4.7F 33H 1F 2 LEGS OF 4 LEDs IN A SERIES 90 8 VIN LX 4 EFFICIENCY (%) 85 VIN=4.2V BAT54HT1
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5
80 VIN=2.7V 75 L=SUMIDA CMD13D1320 30 40 50 60 IO (mA)
70 10
FIGURE 10A. 2 LEGS OF 4 LEDs IN A SERIES
FIGURE 10.
FIGURE 10B. EFFICIENCY vs IO
VIN
L 15H
BAT54HT1
4.7F
1F 95 8 4 EFFICIENCY (%) 90 85 80 75
3 LEGS OF 2 LEDs IN A SERIES
VIN
LX
VIN=4.2V VIN=2.7V
VOUT VCTRL CS 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5 5
70 15
L=SUMIDA CMD13D13-15H 35 55 IO (mA) 75 95
FIGURE 11A. 3 LEGS OF 2 LEDs IN A SERIES
FIGURE 11.
FIGURE 11B. EFFICIENCY vs IO
VIN 4.7F
L 15H
BAT54HT1
1F 95 8 VIN LX 4 EFFICIENCY (%) 90 85 VIN=2.7V 80 75 70 15 L=SUMIDA CMD13D13-15H 35 55 IO (mA) 75 95 3 LEGS OF 3 LEDs IN A SERIES VIN=4.2V
VOUT CS VCTRL 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5 5
FIGURE 12A. 3 LEGS OF 3 LEDs IN A SERIES
FIGURE 12.
FIGURE 12B. EFFICIENCY vs IO
6
EL7513 Typical Performance Curves (Continued) All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
VIN 4.7F L 15H 1F 95 8 VIN LX 4 EFFICIENCY (%) 90 85 VIN=2.7V 80 75 70 15 L=SUMIDA CMD13D13-15H 35 55 IO (mA) 75 95 3 LEGS OF 4 LEDs IN A SERIES BAT54HT1
VIN=4.2V
VOUT VCTRL CS 2 1 0.1F CNTL PGND COMP SGND
3 7 5 6 5 5 5
FIGURE 13A. 3 LEGS of 4 LEDs in a SERIES
FIGURE 13.
FIGURE 13B. EFFICIENCY vs IO
Waveforms
All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
C3=4700pF
IIN VIN IIN 2V/DIV 50mA/DIV VCNTL ILED
50mA/DIV
1V/DIV 10mA/DIV
VCNTL ILED 10ms/DIV
1V/DIV 10mA/DIV
0.1ms/DIV
FIGURE 14. START-UP
FIGURE 15. SHUT-DOWN
ILED=15mA
2V VCNTL 1V 14.2V 12.9V 30mA ILED 15mA
VIN IL
10mV/DIV
100mA/DIV
VO
VLX
10V/DIV
VO 1s/DIV
50mV/DIV
20ms/DIV
FIGURE 16. TRANSIENT RESPONSE
FIGURE 17. CONTINUOUS CONDUCTION MODE
7
EL7513 Waveforms (Continued) All performance curves and waveforms are taken with C1 = 4.7F, C2 = 1F, C3 = 0.1F, L = 33F, VIN = 3.3V, VCNTL = 1V, R1 = 5, 4 LEDs in a series; unless otherwise specified.
VCTRL=0.34V, ILED=5mA
VIN
10mV/DIV VO (5V/DIV)
IL VLX VO 1s/DIV
100mA/DIV VCOMP (1V/DIV)
10V/DIV 50mV/DIV
FIGURE 18. DISCONTINUOUS CONDUCTION MODE
FIGURE 19. OVER VOLTAGE PROTECTION (LED DISCONNECTED)
Detailed Description
The EL7513 is a constant current boost regulator specially designed for driving white LEDs. It can drive up to 4 LEDs in series or 12 LEDs in parallel/series configuration and achieves efficiency up to 91%. The brightness of the LEDs is adjusted through a voltage level on the CNTL pin. When the level falls below 0.1V, the chip goes into shut-down mode and consumes less than 1A of current for VIN less than 5.5V.
The relationship between the LED current and CNTL voltage level is as follows:
V CNTL I LED = ---------------------------13.33 x R 1
When R1 is 5, 1V of VCNTL conveniently sets ILED to 15mA. The range of VCNTL is 250mV to 5.5V.
Shut-Down
When VCNTL is less than 100mV, the converter is in shutdown mode. The max current consumed by the chip is less than 1A for VIN less than 5.5V.
Steady-State Operation
EL7513 is operated in constant frequency PWM. The switching is around 1MHz. Depending on the input voltage, the inductance, the type of LEDs driven, and the LED's current, the converter operates at either continuous conduction mode or discontinuous conduction mode (see waveforms). Both are normal.
Over-Voltage Protection
When an LED string is disconnected from the output, VO will continue to rise because of no current feedback. When VO reaches 18V (nominal), the chip will shut down. The output voltage will drop. When VO drops below 16V (nominal), the chip will boost output voltage again until it reaches 18V. This hiccough continues until LED is applied or converter is shut down. When designing the converter, caution should be taken to ensure the highest operating LED voltage does not exceed 17V, the minimum shut-down voltage. There is no external component required for this function.
Brightness Control
LED's current is controlled by the voltage level on CNTL pin (VCNTL). This voltage can be either a DC or a PWM signal with frequency less than 200Hz (for C3=4700pF). When a higher frequency PWM is used, an RC filter is recommended before the CNTL pin (see Figure 20).
Component Selection
The input and output capacitors are not very important for the converter to operate normally. The input capacitance is normally 0.22F - 4.7F and output capacitance 0.22F - 1F. Higher capacitance is allowed to reduce the voltage/current ripple, but at added cost. Use X5R or X7R type (for its good temperature characteristics) of ceramic capacitors with correct voltage rating and maximum height.
PWM SIGNAL
100K 0.1F
CNTL COMP
FIGURE 20. PWM BRIGHTNESS CONTROL
8
EL7513
When choosing an inductor, make sure the inductor can handle the average and peak currents giving by following formulas (80% efficiency assumed):
IO x VO I LAVG = ----------------------0.8 x V IN 1 I LPK = I LAVG + -- x I L 2 V IN x ( V O - V IN ) I L = -------------------------------------------L x VO x FS
The diode should be Schottky type with minimum reverse voltage of 20V. The diode's peak current is the same as inductor's peak current, the average current is IO, and RMS current is:
I DRMS = I LAVG x I O
Ensure the diode's ratings exceed these current requirements.
White LED Connections
One leg of LEDs connected in series will ensure the uniformity of the brightness. 18V maximum voltage enables 4 LEDs can be placed in series. However, placing LEDs into series/parallel connection can give higher efficiency as shown in the efficiency curves. One of the ways to ensure the brightness uniformity is to prescreen the LEDs.
where: * IL is the peak-to-peak inductor current ripple in Ampere * L inductance in H * FS switching frequency, typical 1MHz A wide range of inductance (6.8H - 68H) can be used for the converter to function correctly. For the same series of inductors, the lower inductance has lower DC resistance (DCR), which has less conducting loss. But the ripple current is bigger, which generates more RMS current loss. Figure 11 shows the efficiency of the demo board under different inductance for a specific series of inductor. For optimal efficiency in an application, it is a good exercise to check several adjacent inductance values of your preferred series of inductors. For the same inductance, higher overall efficiency can be obtained by using lower DCR inductor.
EFFICIENCY vs IO VIN=3.3V FOR DIFFERENT L L=22H L=33H 81 L=10H 79 L=Coilcraft LPO1704 SERIES 1mm HEIGHT 5 10 15 20 25 30 L=15H
PCB Layout Considerations
The layout is very important for the converter to function properly. Power Ground ( ) and Signal Ground ( ) should be separated to ensure the high pulse current in the power ground does not interference with the sensitive signals connected to Signal Ground. Both grounds should only be connected at one point right at the chip. The heavy current paths (VIN-L-LX pin-PGND, and VIN-L-D-C2-PGND) should be as short as possible. The trace connected to the CS pin is most important. The current sense resister R1 should be very close to the pin When the trace is long, use a small filter capacitor close to the CS pin. The heat of the IC is mainly dissipated through the PGND pin. Maximizing the copper area around the plane is preferable. In addition, a solid ground plane is always helpful for the EMI performance. The demo board is a good example of layout based on the principle. Please refer to the EL7513 Application Brief for the layout.
85
EFFICIENCY (%)
83
77
IO (mA)
FIGURE 21. EFFICIENCY OF DIFFERENT INDUCTANCE (4 LEDs IN A SERIES)
9
EL7513 Package Outline Drawing
NOTE: The package drawing shown here may not be the latest version. To check the latest revision, please refer to the Intersil website at
10
EL7513 Package Outline Drawing
NOTE: The package drawing shown here may not be the latest version. To check the latest revision, please refer to the Intersil website at
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Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
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