EL1848IWT-T7A [INTERSIL]
White LED Step-Up Regulator; 白光LED升压型稳压器
| 型号： | EL1848IWT-T7A |
| 厂家： | 
Intersil |
| 描述： | White LED Step-Up Regulator |
| 文件： | 总12页 (文件大小：482K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EL1848
®
Data Sheet
March 31, 2004
FN7427
White LED Step-Up Regulator
Features
The EL1848 is a constant current
• 2.6V to 13.2V input voltage
• 14V maximum output voltage
• Drives up to 9 LEDs, 3 in a series
• 1MHz switching frequency
• Up to 91% efficiency
boost regulator specially designed for
driving white LEDs. It can drive 3
LEDs in series or up to 9 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
• 1µA maximum shut-down current
• Dimming control
1µA of supply current for V less than 5.5V.
IN
The EL1848 is available in 8-pin TSOT and MSOP
packages. The TSOT is just 1mm high, compared to
1.45mm for the standard SOT-23 package.
• 8-pin TSOT and MSOP packages
• Pb-free Available
Applications
• PDAs
Ordering Information
PART
• Cellular phones
• Digital cameras
• White LED backlighting
NUMBER
PACKAGE
8-Pin TSOT
8-Pin TSOT
TAPE & REEL PKG. DWG. #
EL1848IWT-T7
EL1848IWT-T7A
7” (3K pcs)
7” (250 pcs)
7” (3K pcs)
MDP0049
MDP0049
MDP0049
EL1848IWTZ-T7
(See Note)
8-Pin TSOT
(Pb-free)
Typical Connection
D
L
EL1848IWTZ-
8-Pin TSOT
(Pb-free)
7” (250 pcs)
MDP0049
2.6V TO
T7A (See Note)
C
5.5V
C
2
33µH
1
4.7µF
1µF
EL1848IY
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
-
MDP0043
MDP0043
MDP0043
EL1848IY-T7
EL1848IY-T13
7”
VIN
LX
13”
VOUT
CS
NOTE: Intersil Pb-free products employ special Pb-free material
sets; molding compounds/die attach materials and 100% matte tin
plate termination finish, which is compatible with both SnPb and
Pb-free soldering operations. Intersil Pb-free products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed
the Pb-free requirements of IPC/JEDEC J Std-020B.
R
5Ω
1
V
CNTL
PGND
CTRL
COMP SGND
C
3
0.1µF
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2004. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc.
All other trademarks mentioned are the property of their respective owners.
EL1848
Pinouts
EL1848
(8-PIN TSOT)
TOP VIEW
EL1848
(8-PIN MSOP)
TOP VIEW
COMP
CNTL
VOUT
LX
1
2
3
4
8
7
6
5
VIN
CS
VIN
1
2
3
4
8
7
6
5
CNTL
COMP
LX
CS
SGND
PGND
PGND
SGND
VOUT
2
EL1848
Absolute Maximum Ratings (T = 25°C)
A
COMP, CNTL, CS to SGND. . . . . . . . . . . . . . . . . . . . . .-0.3V to +6V
SGND to PGND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Ambient Operating Temperature . . . . . . . . . . . . . . . .-40°C to +85°C
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves
Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 125°C
V
V
to SGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+14V
IN
to SGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+14V
OUT
LX to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+16V
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 areat
the specified temperature and are pulsed tests, therefore: T = T = T
A
J
C
Electrical Specifications
V
= 3V, V = 12V, C = 4.7µF, L = 33µH, C = 1µF, C = 0.1µF, R = 5Ω, T = 25°C, unless otherwise
IN
specified.
O
1
2
3
1
A
PARAMETER
DESCRIPTION
Input Voltage
Total Input Current at Shut-down
CONDITIONS
MIN
TYP
MAX
13.2
1
UNIT
V
V
2.6
IN
I
I
I
V
V
= 0V
µA
mA
µA
V
Q1
CNTL
CNTL
Quiescent Supply Current at V Pin
O
= 1V, load disconnected
1
1.5
20
Q1
COMP Pin Pull-up Current
COMP Voltage Swing
CNTL Shut-down Current
Chip Enable Voltage
COMP connected to SGND
11
1.5
COMP
V
0.5
2.5
1
COMP
I
CNTL = 0V
µA
mV
mV
mA
V
CNTL
V
V
240
CNTL1
Chip Disable Voltage
100
16
CNTL2
I
V
= 1V
V
V
V
= 1V
CNTL
14
13
15
14
12
OUT_ACCURACY
CNTL
V
V
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
rising
15
OUT1
OUT2
OUT
OUT
falling, with resistive load
11
13
V
ILX
400
mA
Ω
R
0.7
DS_ON
I
V
V
V
= 0V, V = 12V
LX
1
µA
kHz
%
LEAK
CNTL
CNTL
F
800
85
1000
90
1200
S
D
= 2V, I = 0
S
MAX
I
1
µA
%/V
CS
∆I /∆V
= 2.6V - 5.5V
IN
0.03
O
IN
Pin Descriptions
PIN NUMBER
PIN NAME
DESCRIPTION
1
2
COMP
CNTL
Compensation pin. A compensation cap (4700pF to 1µF) 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.
3
4
5
6
7
8
VOUT
LX
Output voltage sense. Use for over voltage protection.
Inductor connection pin. The drain of internal MOSFET.
PGND
SGND
CS
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.
VIN
3
EL1848
Block Diagram
2.6V TO
5.5V
C
V
IN
IN
4.7µF
REFERENCE
GENERATOR
1MHz
THERMAL
L
33µH
OSCILLATOR
SHUTDOWN
OVER-VOLTAGE
PROTECTION
V
OUT
LX
C
OUT
1µF
PWM
COMP
+
+
+
LOGIC
C
COMP
0.1µF
BOOST
I(LED)
I-SENSE
START-UP
CONTROL
PGND
PWM
SIGNAL
ERROR AMP
C
S
+
-
5Ω
617K
50K
CNTL
V
CNTL
SGND
Typical Performance Curves
All performance curves and waveforms are taken with C = 4.7µF, C = 1µF, C = 0.1µF, L = 33µF, V = 3.3V, V
= 1V, R = 5Ω, 3 LEDs in a
1
1
2
3
IN
CNTL
series; unless otherwise specified.
1.05
3.5
3
V
=0V, 0.1V
CNTL
WHITE LEDs DISCONNECTED
1.04
1.03
1.02
1.01
1
2.5
2
1.5
1
0.5
0
2.5
3
3.5
4
4.5
5
5.5
2.5
4.5
6.5
8.5
(V)
10.5
12.5
14.5
V
(V)
V
IN
IN
FIGURE 1. SWITCHING FREQUENCY vs V
FIGURE 2. QUIESCENT CURRENT
IN
4
EL1848
Typical Performance Curves (Continued)
All performance curves and waveforms are taken with C = 4.7µF, C = 1µF, C = 0.1µF, L = 33µF, V = 3.3V, V
= 1V, R = 5Ω, 3 LEDs in a
1
1
2
3
IN
CNTL
series; unless otherwise specified.
V
=1V
CNTL
35
30
25
20
15
10
5
16
15.8
15.6
15.4
15.2
15
14.8
14.6
14.4
14.2
14
0
0
0.5
1
1.5
(V)
2
2.5
2.5
3
3.5
4
4.5
5
5.5
V
CNTL
V
(V)
IN
FIGURE 3. I
vs V
FIGURE 4. I
vs V
LED IN
LED
CNTL
BAT54HT1
L
2 LEDs IN A SERIES
V
90
85
80
75
70
IN
33µH
4.7µF
1µF
V
=4.2V
IN
V
=2.7V
IN
8
4
VIN
LX
3
7
5
6
VOUT
CS
5Ω
L=COILCRAFT LPO1704-333CM
10 15 20
(mA)
2
1
V
CNTL PGND
COMP SGND
CTRL
5
25
O
30
I
O
0.1µF
FIGURE 5A. 2 LEDs IN A SERIES
FIGURE 5B. EFFICIENCY vs I
FIGURE 5.
BAT54HT1
L
V
IN
3 LEDs IN A SERIES
33µH
90
85
80
75
70
4.7µF
1µF
V
=4.2V
IN
8
4
VIN
LX
V
=2.7V
IN
3
7
5
6
VOUT
CS
5Ω
2
1
V
CNTL PGND
COMP SGND
CTRL
L=COILCRAFT LPO1704-333CM
10 15 20
(mA)
5
25
O
30
I
0.1µF
O
FIGURE 6B. EFFICIENCY vs I
FIGURE 6A. 3 LEDs IN A SERIES
FIGURE 6.
5
EL1848
Typical Performance Curves (Continued)
All performance curves and waveforms are taken with C = 4.7µF, C = 1µF, C = 0.1µF, L = 33µF, V = 3.3V, V
= 1V, R = 5Ω, 3 LEDs in a
1
1
2
3
IN
CNTL
series; unless otherwise specified.
BAT54HT1
L
2 LEGS OF 2 LEDs IN A SERIES
V
IN
90
85
80
75
70
33µH
4.7µF
1µF
1µF
1µF
V
V
=4.2V
=2.7V
IN
8
4
VIN
LX
IN
3
7
5
6
VOUT
CS
5Ω
5Ω
2
1
V
CTRL
CNTL PGND
COMP SGND
L=COILCRAFT LPO1704-333CM
20 30 40
(mA)
10
50
60
I
O
0.1µF
FIGURE 7A. 2 LEGS OF 2 LEDs IN A SERIES
FIGURE 7B. EFFICIENCY vs I
O
FIGURE 7.
BAT54HT1
L
2 LEGS OF 3 LEDs IN A SERIES
V
IN
33µH
90
85
80
75
70
4.7µF
V
=4.2V
=2.7V
IN
8
4
VIN
LX
V
IN
3
7
5
6
VOUT
CS
5Ω
5Ω
2
1
V
CTRL
CNTL PGND
COMP SGND
L=SUMIDA CMD13D13-33µH
20 30 40
(mA)
10
50
60
I
0.1µF
O
FIGURE 8B. EFFICIENCY vs I
O
FIGURE 8A. 2 LEGS OF 3 LEDs IN A SERIES
FIGURE 8.
BAT54HT1
L
V
IN
3 LEGS OF 2 LEDs IN A SERIES
95
90
85
80
75
70
15µH
4.7µF
V
=4.2V
IN
8
4
VIN
LX
V
=2.7V
IN
3
7
5
6
VOUT
CS
V
CTRL
5Ω
5Ω
5Ω
2
1
L=SUMIDA CMD13D13-15µH
CNTL PGND
COMP SGND
15
35
55
75
95
I
(mA)
O
0.1µF
FIGURE 9A. 3 LEGS OF 2 LEDs IN A SERIES
FIGURE 9B. EFFICIENCY vs I
O
FIGURE 9.
6
EL1848
Typical Performance Curves (Continued)
All performance curves and waveforms are taken with C = 4.7µF, C = 1µF, C = 0.1µF, L = 33µF, V = 3.3V, V
IN
= 1V, R = 5Ω, 3 LEDs in a
1
1
2
3
CNTL
series; unless otherwise specified.
BAT54HT1
V
L
IN
3 LEGS OF 3 LEDs IN A SERIES
95
90
85
80
75
70
15µH
4.7µF
1µF
V
=4.2V
IN
8
4
VIN
LX
V
=2.7V
IN
3
7
5
6
VOUT
CS
V
CTRL
5Ω
5Ω
5Ω
2
1
L=SUMIDA CMD13D13-15µH
CNTL PGND
COMP SGND
15
35
55
75
95
I
(mA)
O
0.1µF
FIGURE 10A. 3 LEGS OF 3 LEDs IN A SERIES
JEDEC JESD51-7 HIGH EFFECTIVE
FIGURE 10B. EFFICIENCY vs I
O
FIGURE 10.
JEDEC JESD51-3 LOW EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD
THERMAL CONDUCTIVITY TEST BOARD
0.6
0.5
0.4
0.3
0.2
0.1
0
1
0.9
870mW
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
486mW
MSOP8/10
MSOP8/10
=115°C/W
θ
=206°C/W
JA
θ
JA
0
25
50
75 85 100
125
0
25
50
75 85 100
125
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
FIGURE 12. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
FIGURE 11. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
7
EL1848
Waveforms
All performance curves and waveforms are taken with C = 4.7µF, C = 1µF, C = 0.1µF, L = 33µF, V = 3.3V, V
IN
= 1V, R = 5Ω, 4 LEDs in a
1
2
3
CNTL
1
series; unless otherwise specified.
C =4700pF
3
I
50mA/DIV
IN
V
I
IN
2V/DIV
50mA/DIV
V
1V/DIV
IN
CNTL
I
10mA/DIV
LED
V
1V/DIV
CNTL
I
10mA/DIV
LED
0.1ms/DIV
10ms/DIV
FIGURE 14. SHUT-DOWN
FIGURE 13. START-UP
I
=15mA
LED
2V
1V
10mV/DIV
∆V
IN
V
CNTL
I
100mA/DIV
L
14.2V
12.9V
V
O
30mA
V
10V/DIV
LX
I
LED
15mA
∆V
50mV/DIV
O
1µs/DIV
20ms/DIV
FIGURE 15. TRANSIENT RESPONSE
FIGURE 16. CONTINUOUS CONDUCTION MODE
V
=0.34V, I =5mA
CTRL LED
∆V
10mV/DIV
IN
V
V
(5V/DIV)
O
I
100mA/DIV
L
(1V/DIV)
V
COMP
LX
10V/DIV
∆V
50mV/DIV
O
1µs/DIV
FIGURE 17. DISCONTINUOUS CONDUCTION MODE
FIGURE 18. OVER VOLTAGE PROTECTION (LED
DISCONNECTED)
8
EL1848
hiccough continues until LED is applied or converter is shut
Detailed Description
down.
The EL1848 is a constant current boost regulator specially
designed for driving white LEDs. It can drive up to 3 LEDs in
series or 9 LEDs in parallel/series configuration and
achieves efficiency up to 91%.
When designing the converter, caution should be taken to
ensure the highest operating LED voltage does not exceed
13V, the minimum shut-down voltage. There is no external
component required for this function.
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
Component Selection
The input and output capacitors are not very important for
the converter to operate normally. The input capacitance
is normally 0.22µF - 4.7µF and output capacitance
0.22µF - 1µF. 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.
1µA of current for V less than 5.5V.
IN
Steady-State Operation
EL1848 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.
When choosing an inductor, make sure the inductor can
handle the average and peak currents giving by following
formulas (80% efficiency assumed):
Brightness Control
LED’s current is controlled by the voltage level on CNTL pin
I × V
O O
I
= -----------------------
LAVG
(V
). This voltage can be either a DC or a PWM signal
0.8 × V
CNTL
IN
with frequency less than 200Hz (for C =4700pF). When a
3
higher frequency PWM is used, an RC filter is recommended
before the CNTL pin (see Figure 17).
1
2
--
I
= I
+
× ∆I
LPK
LAVG
L
V
× (V – V
IN
)
IN
O
∆I = --------------------------------------------
L
L × V × F
O
S
where:
100K
PWM
CNTL
• ∆I is the peak-to-peak inductor current ripple in Ampere
L
SIGNAL
0.1µF
COMP
• L inductance in µH
• FS switching frequency, typical 1MHz
A wide range of inductance (6.8µH - 68µH) 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 9
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.
FIGURE 19. PWM BRIGHTNESS CONTROL
The relationship between the LED current and CNTL voltage
level is as follows:
V
CNTL
I
= ----------------------------
LED
13.33 × R
1
When R is 5Ω, 1V of V
conveniently sets I to
LED
1
CNTL
is 250mV to 5.5V.
15mA. The range of V
CNTL
Shut-Down
When V
is less than 100mV, the converter is in shut-
CNTL
down mode. The max current consumed by the chip is less
than 1µA for V less than 5.5V.
IN
Over-Voltage Protection
When an LED string is disconnected from the output, V will
O
continue to rise because of no current feedback. When V
O
reaches 14V (nominal), the chip will shut down. The output
voltage will drop. When V drops below 11V (nominal), the
O
chip will boost output voltage again until it reaches 14V. This
9
EL1848
For the same inductance, higher overall efficiency can be
obtained by using lower DCR inductor.
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 pre-
screen the LEDs.
EFFICIENCY vs I
O
85
V
=3.3V FOR
IN
PCB Layout Considerations
DIFFERENT L
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
L=22µH
83
81
79
77
L=33µH
L=15µH
L=10µH
L=Coilcraft
paths (V -L-L pin-PGND, and V -L-D-C -PGND) should
IN IN
X
2
LPO1704 SERIES
1mm HEIGHT
be as short as possible.
5
10
15
20
(mA)
25
30
The trace connected to the CS pin is most important. The
current sense resister R should be very close to the pin
I
O
1
When the trace is long, use a small filter capacitor close to
the CS pin.
FIGURE 20. EFFICIENCY OF DIFFERENT INDUCTANCE
(4 LEDs IN A SERIES)
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 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 I , and RMS
O
current is:
The demo board is a good example of layout based on the
principle. Please refer to the EL1848 Application Brief for the
layout.
I
=
I
× I
LAVG O
DRMS
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. 14V maximum voltage enables
3 LEDs can be placed in series.
10
EL1848
TSOT Package Outline Drawing
11
EL1848
MSOP 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
<http://www.intersil.com/design/packages/index.asp>
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
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.
For information regarding Intersil Corporation and its products, see www.intersil.com
12
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