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AME
AME5144
n General Description
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
n Features
l Up to 10 LEDs at 25mA l 86% Efficiency l 1.7% Current-Regulation Accuracy l Output Overvoltage Protection l Flexible Dimming Control Analog Direct-PWM Internal Filter l 1MHz PWM Switching Frequency l 0.1uF Output Capacitor l Soft-Start Eliminates Inrush Current l 2.6V to 5.5V Input Range l 0.3uA Shutdown current l DFN 3mm x 3mm x 0.75mm Package with Exposed Paddle l All AME' s Lead Free Products Meet RoHS Standards
The AME5144 is an efficient driver for up to ten white LED applications. They are ideal for large LCD backlight displays in Cell Phone, PDAs, and other handheld devices. The AME5144 is switch-mode boost converter with constant LED current, rather than output voltage. The series connection allows the LED currents to be identical for uniform brightness and minimizes the number of trace to the LEDs. The AME5144 drives series-connected LEDs to controlled-current pin which connected a typically 13 sense resistor, not an expensive fraction-ohm value. Fast 1MHz current-mode PWM operation allows for small input and output capacitors and a small inductor while minimizing ripple on the input supply/battery. Soft-start eliminates inrush current during startup. To control LED brightness, the LED current can be pulsed by applying a single analog/PWM signal with a frequency range from 200Hz to 30KHz for the control pin CTRL. The AME5144 is available in space saving, 8 pin, 3mm x 3mm x 0.75mm DFN package.
n Applications
l Cell Phones and Smart Phones l PDAs, Palmtops, and Wireless Handhelds l e-Books and Subnotebooks l White LED Display Backlighting S ie C
Rev.D.01
1
AME
AME5144
n Typical Application
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
L=22H VIN CIN
2.2F
Output Up to 37V SW COUT 0.1F
OUT
AME5144
Analog or PWM Dimming IN CTRL PGND GND
200Hz to 30KHz
CS
COMP CCOMP 0.1F 2 to 10 LEDs RSENSE 13
n Function Block Diagram
170mV 8.2ms CTRL Bright Control CS SW Ramp Generator PWM Control Driver PGND OVLO Gm OUT
Shutdown
Comp
GND Current Limit
Oscillator
UVP
IN
2
Rev. D.01
AME
AME5144
n Pin Configuration
DFN-8C (3mmx3mmx0.75mm) Top View
8 7 6 5
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
AME5144-AVAxxx 1. OUT 2. IN 3. CTRL 4. CS
AME5144
5. COMP 6. GND 7. PGND * Die Attach: Conductive Epoxy
1
2
3
4
8. SW
n Pin Description
Pin Number Pin Name Pin Description
Overvoltage Sense. When OUT is greater than 38.5V(Typ.), the internal nchannel MOSFET turns off until OUT drops below 37V(Min), then the IC reenters soft-start Connect a 0.1uf ceramic capacitor from OUT to ground. In shutdown, VOUT is one diode drop below VIN . C Input Voltage Supply. The input voltage range is 2.6V to 5.5V. Connect a 2.2uF ceramic capacitor from IN to GND. Brightness Control pin. Either an Analog or PWM control signal can be used. ie The PWM signal must be between 200Hz and 30KHz. Varying the voltage from +0.24V to +1.65V adjusts the brightness from dim to 100% brightness, respectively. Any voltage above +1.65V does not increase brightness. Hold CTRL below 100mV to shut down the IC after an 8.2ms delay. Current Sense Feedback input. Connect a resistor from CS to GND to set the LED bias current. The voltage at CS regulates to VCRTL/5 or 0.330V. Compensation input. Connect a 0.1F Ceramic Capacitor(Ccomp) from COMP to GND. Ccomp stabilizes the converter, controls soft-start and lowpass filters direct PWM dimming at CTRL. Ccomp discharges to 0V through an internal 20K resistor in showdown. Ground. Connect to PGND and exposed pad directly under the IC. Power Ground. Connect to PGND and exposed pad directly under the IC. Inductor Connection. Connect SW to the node between the inductor and schottky diode. SW is high impedance in shutdown.
3
1
OUT
2
IN
3
CTRL
4
CS
5
COMP
6 7 8
Rev.D.01
GND PGND SW
AME
AME5144
n Ordering Information AME5144 - x x x xxx
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Output Voltage Number of Pins Package Type Pin Configuration & Special Feature
Pin Configuration & Special Feature A
(DFN-8C)
Package Type V: DFN
Number of Pins A: 8
Output Voltage
1. OUT 2. IN 3. CTRL 4. CS 5. COMP 6. GND 7. PGND 8. SW
ADJ: Adjustable
n Available Options
Part Number
AME5144-AVAADJ
Marking*
A5144 AMYMXX
Output Voltage
ADJ
Package
DFN-8C
Operating Ambient Temperature Range
-40OC to +85OC
Note: 1. The first 2 places represent product code. It is assigned by AME such as AM. 2. Y is year code and is the last number of a year. Such as the year code of 2008 is 8. 3. A bar on top of first letter represents Green Part such as A5144. 4. The last 3 places MXX represent Marking Code. It contains M as date code in "month", XX as LN code and that is for AME internal use only. Please refer to date code rule section for detail information. 5. Please consult AME sales office or authorized Rep./Distributor for the availability of output voltage and package type.
4 Rev. D.01
AME
AME5144
n Absolute Maximum Ratings
Parameter
VIN , to GND CTRL, CS, COMP, to GND SW, OUT to GND PGND to GND ESD Classification
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Maximum
-0.3 to 6.0 -0.3 to (V IN + 0.3) -0.3 to 40 -0.3 to 0.3 B*
Unit
V V V V
Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device. * HBM B: 2000V ~ 3999V
n Recommended Operating Conditions
Parameter
Storage Temperature Range Ambient Temperature Range Junction Temperature Range C
Rating
-65 to +150 -40 to +85 -40 to +125
Unit
o
C C C
o
o
n Thermal Information
Parameter
Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Solder Iron (10 Sec)** DFN-8C
ie
Package
Die Attach
Symbol
JC
Maximum
17
Unit
o
C/W
Conductive Epoxy
JA PD
125
o
C/W mW
o
800 350
C
* Measure JC on backside center of molding compund if IC has no tab. ** MIL-STD-202G 210F
Rev.D.01 5
AME
AME5144
n Electrical Specifications
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
VIN = 3V, L=22H, CIN=2.2F, COUT=0.1F, CCOMP=0.1F, RSENSE =13, TA = 25oC, unless otherwise noted.
Parameter Input voltage Adjustable Output Range Input Undervoltage Locked Input Undervoltage Locked Hysteresis Quiescent Current Shutdown Current Over Voltage Protection Over Voltage Protection Hysteresis OUT Input Bias Current Symbol VIN VOUT UVP UVP Hysteresis IQ ISHDN OVP OVP,HYST VOUT=32V, VCTRL>0.24V IB,OUT OUT=IN, CTRL=GND VCTRL=1.5V, VIN=2.6V to 5.5V VCS=VCTRL/5 VCTRL=3V 310 9 No Switching, VCS=0.5V CTRL=GND, VOUT=VIN VOUT Rising 37 Note 1 Rising edge Test Condition Min 2.6 VIN -VD 2.10 2.38 30 0.5 0.3 38.5 2 20 0.01 35 A 1 V A mV V 780 240 K mV mV 10.5 mS 0.7 2 40 Typ Max Units 5.5 37 2.55 V V V mV mA A V V
CTRL to CS Regulation CS Input Bias Current CS Maximum Brightness Clamp Voltage CTRL Voltage for CS Maximum Brightness Clamp CTRL Input Resistance CTRL Dual-Mode Threshold CTRL Dual-Mode Hysteresis CTRL Shutdown Enable Delay
VCS ICS VCS(MAX) VCTRL(MAX) RCTRL VDM VDM Hysteresis
0.290 0.300 0.310 0.01 330 1.65 1 347
VCTRL<=1.5V
250 100
500 170 5
Note 2
6.0
8.2
6
Rev. D.01
AME
AME5144
n Electrical Specifications (contd.)
Parameter CS to Comp Transconductance COMP Input Resistance to Ground Switch Frequency Minimum Duty Cycle Maximum Duty Cycle Switch On-Resistance Switch Leakage Current Switch Current Limit fOSC Symbol Gm
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Test Condition VCOMP=1.5V In shutdown, UVLO or OVLO
Min 32
Typ 50 20
Max Units 82 S K 1.25 MHz %
0.75 PWM Mode
1.0 12 0
DMIN DMAX RDS,ON ISW,LK ISW,CL
Pulse Skipping CTRL=IN, CS=GND ISW =190mA VSW =37V, CTRL=GND Duty Cycle=90% 500 94
95 0.8 0.01 700 1.35 5 900
% mA
Note 1: VD is the forward-voltage drop of the Schottky diode in Typical Application. Note 2: Time from CTRL going below the Dual-Mode threshold to IC shutdown.
C
ie
Rev.D.01
7
AME
AME5144
n Detailed Description
The high efficiency and small size of the AME5144 make them ideally suited to driver up to ten series-connected LEDs. They operate as a boost DC-DC converter that controls output current rather than voltage. A low 300mV current-sense threshold minimized the losses. The AME5144 provide even illumination by sourcing the same output current through each LED, eliminating the need for expensive factory calibration. The fast 1MHz internal oscillator allows for small inductor and small input and output capacitors while minimizing input and output ripple. The single analog control input (CTRL) allows easy adjustment of LED brightness and on/off control. This allows simple logic-level on/off control, analog voltage control, or PWM duty-cycle control of both brightness and shutdown. In shutdown, supply current is reduced to a low 0.3A (Typ.). A soft-start gradually illuminates the LEDs, eliminating the inrush current during startup.
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Over Voltage Protection OVP is designed to prevent the output voltage from exceeding the maximum switch voltage rating of 38.5V (Typ.). The protection circuitry stops the internal MOSFET from switching. There is a 1.5V hysteresis associated with this circuitry which will cause the output to fluctuate between 38.5V and 37V.
Adjusting LED Current Adjusting the output current of the AME5144 changes the brightness of the LEDs. An analog input (CTRL) and the sense-resistor values set the output current. Output current is given by: ILED =VCTRL/(5xRSENSE) The VCTRL voltage range for adjusting output current is 0.24V to 1.65V. To set maximum current, calculate RSENSE when VCTRL is at its maximum as follows: RSENSE=1.65V / (5 x ILED ) Power dissipation in RSENSE is typical less than 10mW, allowing the use of small surface-mount resistor.
Shutdown The AME5144 enter shutdown when VCTRL is less than 100mV for more than 8.2ms. When shutdown, the supply current is reduced to 0.3A (Typ.) approximately. The 0.3uA supply current is applied for the voltage-detection circuitry. CCOMP is discharge during shutdown, allowing the device to reinitiate soft-start when enabled. Although the internal n-channel MOSFET does not switch in shutdown, there is still a DC current path between the input and the LEDs through the inductor and Schottky diode. The minimum forward voltage of the LED array must exceed the maximum input voltage to ensure that the LEDs remain off in shutdown. However, with two or more LEDs, the forward voltage is enough to keep leakage current low, less than 1A (Typ.).
PWM Dimming Control A. Using DC Signal for CTRL Pin For CTRL, applying a DC signal in the range of 0.24V to 1.65V control the LED current. CTRL can be overdriven; however, applying a CTRL greater than 1.65V does not increased the LED current above the level at 1.65V. B. Using PWM signal for CTRL pin c The CTRL input is used as a digital input allowing LED brightness control with a logic-level PWM signal applied directly to CTRL. The frequency range is from 200Hz to 30KHz, while 0% duty cycle corresponds to minimum current, and 100% duty cycle corresponds to full current. The error amplifier and compensation capacitor form a low pass filter so PWM dimming results in DC current to the LEDs without the need for any additional RC filters.
Soft-Start The AME5144 attain soft-start by charging CCOMP gradually with a current source. When V COMP rises above 1.25V, the internal MOSFET begins switching at a reduced duty cycle. When VCOMP rises above 2.25V, the duty cycle is at its maximum. See the Typical Operation Characteristics for an example of soft-start operation.
8
Rev. D.01
AME
AME5144
Capacitor Selection Ceramic capacitors with X5R, X7R, or better dielectric are recommended for stable operation over the entire operating temperature range. The exact values of input and output capacitors are not critical. The typical value for input capacitor is 2.2F, and the typical value for output capacitor is 0.1F. Higher values capacitors can be used to reduce input and output ripple, but at the expense of size and higher cost. CCOMP stabilizes the converter and control soft-start. Connect a 0.1F capacitor from COMP to GND.
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Schottky Diode Selection The high switching frequency of the AME5144 demands a high-speed rectification diode (D1) for optimum efficiency. A Schottky diode is recommended due to its fast recovery time and low forward-voltage drop. Ensure that the diode's average and peak current rating exceed the average output current and peak inductor current. In addition, the diode's reverse breakdown voltage must exceed V OUT. The RMS diode current can be approximated from:
I DIODE( RMS) = I OUT x I PEAK
200mA, 40V Schottky diode SOD-523 or Central Semiconductor CMOSH-4E are recommended for applications.
Inductor Selection Inductor values range from 10H to 47H. A 22H inductor optimizes the efficiency for most applications while maintaining low 12mVp-p input ripple. Inductor with low DCR can be more efficiency. To prevent core saturation, ensure that the inductor-saturation current rating exceeds the peak inductor current for the application. Calculate the peak inductor current with the following formula:
Layout Consideration Due to fast switching waveforms and high-current paths, careful PC board layout is required. When laying out a board, minimum trace lengths between the IC and RSENSE, the inductor, the diode, the input capacitor and output capacitor. Keep trace short and wide. Keep noisy traces, such as the SW node trace, away from CS.
I PEAK =
VOUT ( MAX ) x I LED( MAX ) 0.9 x VIN ( MIN )
+
VIN ( MIN ) x 0.9us 2x L
22H, 250mA inductor Murata LQH32CN220K and The input bypass capacitor CIN should be placed as close C to the IC as possible. This will reduce copper trace resisSumida CDRH5D16NP- 220MB are recommended. tance, which effect the input voltage ripple of the IC. The output capacitor, COUT, should also be placed close to the i e IC and connected directly between the OUT and GND pins. PGND and GND should be connected directly to the exposed paddle underneath the IC. The ground connections of CIN and COUT should be as close together as possible. Any copper trace connections with the COUT capacitor can increase the series resistance which directly effects output ripple and efficiency. The current setting resistor, RSENSE, should be kept close to the CS pin to minimize copper trace connections that can inject noise in to the system. The traces from IN to the inductor and from Schottky diode to the LEDs can be longer.
Rev.D.01
9
AME
AME5144
Duty Cycle The maximum duty cycle of the switching regulator determines the maximum boost ratio of output-to-input voltage that the converter can attain in mode of operation. The duty cycle for a given boost application is defined as: This applies for continuous mode operation.
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
D=
VOUT + VDIODE - V IN VOUT + VDIODE - VSW
Calculating Load Current The load current is related to the average inductor current by the relation: ILOAD = IIND (AVG) x (1 - D) Where " D" is the duty cycle of the application. The switch current can be found by: ISW = IIND (AVG) + 1 /2 (IRIPPLE) Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency: IRIPPLE = D x (V IN-V SW) / (f x L) Combining all terms, we can develop an expression which allows the maximum available load current to be calculated:
ILOAD = ( 1-D ) x ( ISW (max) -
D ( VIN-VSW ) 2fL
)
10
Rev. D.01
AME
AME5144
Efficiency vs Input Voltage
100 95 90 85
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Efficiency vs LED Current
95 90
3 LEDs 4 LEDs
85
3 LEDs
6 LEDs
Efficiency(%)
Efficiency(%)
80 75 70 65 60 55 50 45 2 3 4 5 6
80 75
6 LEDs 8 LEDs 10 LEDs
10 LEDs
70 65 60 55 50 0 5 10 15
8 LEDs
20
25
Input Voltage(V)
LED Current(mA)
LED Current vs Direct-PWM Dimming
30
LED Current vs Ambient Temperature
26 24
25
22
LED Current(mA)
LED Current(mA)
20
20 18
15
ILED =15mA
16 14 12
10
5
C
0 0 20 40 60 80 100
10 8 -40
-20
0
20
40
60
80
100
Duty Cycle(%)
Temperature(o C)
ie
Switching Waveforms Soft-Start And Shutdown Response
VIN
20mV/div AC-coupled
VCTRL
2V/div
VLX
10V/div
IIN
100mA/div
VOUT
200mV/div AC-coupled
ILED
50mA/div
IL
100mA/div
VOUT
10V/div
400 ns/div
20ms/div
Rev.D.01
11
AME
AME5144
Ctrl Step Response
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
Direct-PWM Dimming Response
V CTRL
1V/ div
VCTRL
2V/div 32kHZ 50% Duty cycle 20mV/div AC -coupled
IIN
100mA/div
V IN
ILED
50mA/div
V OUT
500 mV/div AC -coupled 10m A/div
I LED
VOUT 10V /div
20ms /div
10s/div
VFB vs VIN
310 308 306 304
TA = -40OC
VF B(mV)
302 300 298 296 294 292 290 2.6 3.6 4.6 5.6
TA =85OC
T A=25OC
VIN(V)
12
Rev. D.01
AME
AME5144
n Date Code Rule
Month Code 1: January 7: July 2: February 8: August 3: March 9: September 4: April A: October 5: May B: November 6: June C: December
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
n Tape and Reel Dimension
DFN-8C (3mmx3mmx0.75mm)
P
PIN 1
C
W
AME
Carrier Tape, Number of Components Per Reel and Reel Size
AME
ie
Package DFN-8C (3x3x0.75mm)
Carrier Width (W) 12.00.1 mm
Pitch (P) 4.00.1 mm
Part Per Full Reel 3000pcs
Reel Size 3301 mm
Rev.D.01
13
AME
AME5144
n Package Dimension
DFN-8C (3mmx3mmx0.75mm)
D
High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs
b
e
L E E1
PIN #1
TOP VIEW
D1 BOTTOM VIEW
A REAR VIEW
G1
G
SYMBOLS A D E e D1 E1 b L G G1
MILLIMETERS MIN 0.700 2.900 2.900 0.600 2.200 1.400 0.200 0.375 0.153 0.000 MAX 0.800 3.100 3.100 0.700 2.400 1.600 0.320 0.575 0.253 0.050
INCHES MIN 0.028 0.114 0.114 0.024 0.087 0.055 0.008 0.015 0.0060 0.0000 MAX 0.031 0.122 0.122 0.028 0.094 0.063 0.013 0.023 0.010 0.002
14
Rev. D.01
www.ame.com.tw
E-Mail: sales@ame.com.tw
Life Support Policy: These products of AME, Inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of AME, Inc. AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. (c) AME, Inc. , December 2008 Document: 1241-DS5144-D.01
Corporate Headquarter
AME, Inc.
2F, 302 Rui-Guang Road, Nei-Hu District Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989

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