AME5144 AMETHERM | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 15
Technical content
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs 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 con- stant LED current, rather than output voltage. The series connection allows the LED currents to be identical for uni- form 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 Ω 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 mini- mizing ripple on the input supply/battery. Soft-start elimi- nates inrush current during startup. To control LED bright- ness, 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 General Description n Features n Applications S l Cell Phones and Smart Phones l PDAs, Palmtops, and Wireless Handhelds l e-Books and Subnotebooks l White LED Display Backlighting
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Typical Application n Function Block Diagram CS Driver SW OUT Comp GND PGND IN CTRL 170mV Shutdown PWM Control Current Limit OVLO UVP Gm Ramp Generator Oscillator Bright Control 8.2ms OUT IN CTRL CS SW PGND COMP GND RSENSE 13Ω L=22µH AME5144 VIN CCOMP 0.1µF Output Up to 37V COUT 0.1µF CIN 2.2µF 2 to 10 LEDs 200Hz to 30KHz Analog or PWM Dimming
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Pin Configuration DFN-8C (3mmx3mmx0.75mm) Top View AME5144-AVAxxx 1. OUT 2. IN 3. CTRL 4. CS 5. COMP 6. GND 7. PGND * Die Attach: 8. SW Conductive Epoxy n Pin Description 8 7 6 1 2 3 4 AME5144 Pin Number Pin Name Pin Description
1 OUT
Overvoltage Sense. When OUT is greater than 38.5V(Typ.), the internal n- channel 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. 2 IN Input Voltage Supply. The input voltage range is 2.6V to 5.5V. Connect a 2.2uF ceramic capacitor from IN to GND.
3 CTRL
Brightness Control pin. Either an Analog or PWM control signal can be used. 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. 4 CS 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.
5 COMP
Compensation input. Connect a 0.1µF 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 20KΩ resistor in showdown. 6 GND Ground. Connect to PGND and exposed pad directly under the IC. 7 PGND Power Ground. Connect to PGND and exposed pad directly under the IC. 8 SW Inductor Connection. Connect SW to the node between the inductor and schottky diode. SW is high impedance in shutdown.
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Ordering Information n Available Options AME5144 - x x x xxx Pin Configuration & Special Feature Package Type Number of Pins Output Voltage 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. A 1. OUT V: DFN A: 8 ADJ: Adjustable (DFN-8C) 2. IN 3. CTRL 4. CS 5. COMP 6. GND 7. PGND 8. SW Pin Configuration & Special Feature Package Type Number of Pins Output Voltage Part Number Marking* Output Voltage Package Operating Ambient Temperature Range AME5144-AVAADJ A5144 AMYMXX ADJ DFN-8C -40OC to +85OC
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Absolute Maximum Ratings n Recommended Operating Conditions Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device. * HBM B: 2000V ~ 3999V Parameter Maximum Unit VIN, to GND -0.3 to 6.0 V CTRL, CS, COMP, to GND -0.3 to (VIN + 0.3) V SW, OUT to GND -0.3 to 40 V PGND to GND -0.3 to 0.3 V ESD Classification B* n Thermal Information * Measure θ JC on backside center of molding compund if IC has no tab. ** MIL-STD-202G 210F Parameter Rating Unit Storage Temperature Range -65 to +150 oC Ambient Temperature Range -40 to +85 oC Junction Temperature Range -40 to +125 oC Parameter Package Die Attach Symbol Maximum Unit Thermal Resistance* (Junction to Case) θ JC 17 oC / W Thermal Resistance (Junction to Ambient) θ JA 125 oC / W Internal Power Dissipation PD 800 mW 350 oC DFN-8C Solder Iron (10 Sec)** Conductive Epoxy
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Electrical Specifications VIN = 3V, L=22µH, CIN=2.2µF, COUT=0.1µF, CCOMP=0.1µF, RSENSE =13Ω , TA = 25oC, unless otherwise noted. Parameter Symbol Min Typ Max Units Input voltage VIN 2.6 5.5 V Adjustable Output Range VOUT VIN-VD 37 V Input Undervoltage Locked UVP 2.10 2.38 2.55 V Input Undervoltage Locked Hysteresis UVP Hysteresis 30 mV Quiescent Current IQ 0.5 0.7 mA Shutdown Current ISHDN 0.3 2 µA Over Voltage Protection OVP 37 38.5 40 V Over Voltage Protection Hysteresis OVP,HYST 2 V 9 20 35 0.01 1 CTRL to CS Regulation VCS 0.290 0.300 0.310 V CS Input Bias Current ICS 0.01 1 µA CS Maximum Brightness Clamp Voltage VCS(MAX) 310 330 347 mV CTRL Voltage for CS Maximum Brightness Clamp VCTRL(MAX) 1.65 V CTRL Input Resistance RCTRL 250 500 780 KΩ CTRL Dual-Mode Threshold VDM 100 170 240 mV CTRL Dual-Mode Hysteresis VDM Hysteresis 5 mV CTRL Shutdown Enable Delay 6.0 8.2 10.5 mSNote 2 VCS=VCTRL/5 OUT Input Bias Current IB,OUT µA VOUT Rising OUT=IN, CTRL=GND VOUT=32V, VCTRL>0.24V VCTRL=3V VCTRL<=1.5V Test Condition No Switching, VCS=0.5V Rising edge Note 1 CTRL=GND, VOUT=VIN VCTRL=1.5V, VIN=2.6V to 5.5V
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Electrical Specifications (contd.) 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. Parameter Symbol Min Typ Max Units CS to Comp Transconductance Gm 32 50 82 µS COMP Input Resistance to Ground 20 KΩ Switch Frequency fOSC 0.75 1.0 1.25 MHz Maximum Duty Cycle DMAX 94 95 % Switch On-Resistance RDS,ON 0.8 1.35 Ω Switch Leakage Current ISW,LK 0.01 5 µΑ Switch Current Limit ISW,CL 500 700 900 mA ISW=190mA In shutdown, UVLO or OVLO DMINMinimum Duty Cycle PWM Mode Test Condition Duty Cycle=90% CTRL=IN, CS=GND VCOMP=1.5V VSW=37V, CTRL=GND Pulse Skipping
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs 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 con- trols output current rather than voltage. A low 300mV cur- rent-sense threshold minimized the losses. The AME5144 provide even illumination by sourcing the same output cur- rent through each LED, eliminating the need for expensive factory calibration. The fast 1MHz internal oscillator al- lows for small inductor and small input and output capaci- tors while minimizing input and output ripple. The single analog control input (CTRL) allows easy ad- justment 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 0.3 µA (Typ.). A soft-start gradually illuminates the LEDs, elimi- nating the inrush current during startup. Shutdown The AME5144 enter shutdown when VCTRL is less than 100mV for more than 8.2ms. When shutdown, the supply current is reduced to 0.3µA (Typ.) approximately. The 0.3uA supply current is applied for the voltage-de- tection circuitry. C COMP is discharge during shutdown, al- lowing the device to reinitiate soft-start when enabled. Al- though 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 di- ode. 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 1µA (Typ.). Soft-Start The AME5144 attain soft-start by charging CCOMP gradu- ally with a current source. When VCOMP rises above 1.25V, the internal MOSFET begins switching at a reduced duty cycle. When V COMP rises above 2.25V, the duty cycle is at its maximum. See the Typical Operation Characteris- tics for an example of soft-start operation. c Over Voltage Protection OVP is designed to prevent the output voltage from ex- ceeding 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 be- tween 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. 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 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 cur- rent, 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.
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs Capacitor Selection Ceramic capacitors with X5R, X7R, or better dielectric are recommended for stable operation over the entire op- erating temperature range. The exact values of input and output capacitors are not critical. The typical value for input capacitor is 2.2 µF, and the typical value for output capacitor is 0.1µF. Higher values capacitors can be used to reduce input and output ripple, but at the expense of size and higher cost. C COMP stabilizes the converter and control soft-start. Connect a 0.1 µF capacitor from COMP to GND. Inductor Selection Inductor values range from 10µH to 47 µH. A 22 µH in- ductor 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: 22 µH, 250mA inductor Murata LQH32CN220K and Sumida CDRH5D16NP- 220MB are recommended. L usV V IVI MININ MININ MAXLEDMAXOUT PEAK ×+× ×= 2 9.0 9.0 )()( 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 out- put current and peak inductor current. In addition, the diode's reverse breakdown voltage must exceed VOUT. The RMS diode current can be approximated from: 200mA, 40V Schottky diode SOD-523 or Central Semi- conductor CMOSH-4E are recommended for applications. 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 ca- pacitor. Keep trace short and wide. Keep noisy traces, such as the SW node trace, away from CS. The input bypass capacitor CIN should be placed as close to the IC as possible. This will reduce copper trace resis- tance, which effect the input voltage ripple of the IC. The output capacitor, COUT, should also be placed close to the IC and connected directly between the OUT and GND pins. PGND and GND should be connected directly to the ex- posed 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 out- put 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. PEAKOUTRMSDIODE III ×=)(
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs Duty Cycle The maximum duty cycle of the switching regulator de- termines the maximum boost ratio of output-to-input volt- age 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. VOUT + VDIODE - VIN VOUT + VDIODE - VSW D = Calculating Load Current The load current is related to the average inductor cur- rent 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 (VIN-VSW) / (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
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs Efficiency vs Input Voltage Efficiency vs LED Current LED Current vs Direct-PWM Dimming LED Current vs Ambient Temperature Switching Waveforms Soft-Start And Shutdown Response -40 -20 0 20 40 60 80 100 Temperature(oC) LED Current(mA) ILED=15mA VIN VLX VOUT IL 20mV/div AC-coupled 10V/div 200mV/div AC-coupled 100mA/div 400ns/div 100 2 3 4 5 6 Input Voltage(V) Efficiency(%)
3 LEDs
4 LEDs
6 LEDs
8 LEDs
10 LEDs
Duty Cycle(%) LED Current(mA) 0 5 10 15 20 25 LED Current(mA) Efficiency(%)
3 LEDs 6 LEDs
8 LEDs10 LEDs
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs Ctrl Step Response Direct-PWM Dimming Response VCTRL IIN ILED VOUT 1V/div 100mA/div 50mA/div 10V/div 20ms/div VCTRL VIN VOUT ILED 2V/div 32kHZ 50% Duty cycle 20mV /div AC -coupled 500 mV/div AC -coupled 10mA/div 10ms/div VFB vs VIN 290 292 294 296 298 300 302 304 306 308 310 2.6 3.6 4.6 VIN(V) VFB(mV) 5.6 TA= -40OC TA=25OCTA=85OC
Rev.D.01 C ie High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Tape and Reel Dimension Carrier Tape, Number of Components Per Reel and Reel Size DFN-8C (3mmx3mmx0.75mm) W P PIN 1 AME AME Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size DFN-8C n Date Code Rule 1: January 7: July 2: February 8: August 3: March 9: September 4: April A: October 5: May B: November 6: June C: December Month Code
Rev. D.01 High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs n Package Dimension DFN-8C (3mmx3mmx0.75mm) MIN MAX MIN MAX A 0.700 0.800 0.028 0.031 D 2.900 3.100 0.114 0.122 E 2.900 3.100 0.114 0.122 e 0.600 0.700 0.024 0.028 D1 2.200 2.400 0.087 0.094 E1 1.400 1.600 0.055 0.063 b 0.200 0.320 0.008 0.013 L 0.375 0.575 0.015 0.023 G 0.153 0.253 0.0060 0.010 G1 0.000 0.050 0.0000 0.002 SYMBOLS MILLIMETERS INCHES TOP VIEW BOTTOM VIEW REAR VIEW e D E A GG1 b L PIN #1
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. 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 www.ame.com.tw E-Mail: sales@ame.com.tw