PAM2842-Rev 1.1

Typical Application Circuit PAM2842 High Power LED Driver Features Applications Output Power up to 30W Chip Enable with Soft-start Analog and PWM Dimming Low Quiescent Current Over Current Protection Over Voltage Protection Thermal Protection UVLO Tiny Pb-Free Packages : 40-Pin QFN6x6 and TSSOP-20 Home Lighting Automotive Lighting Monitor Backlighting protection protection LED dimming can be done by using a PWM signal to the COMP pin. 40-Pin QFN6x6 and � � � Description The PAM2842 is a high power LED driver, capable of driving up to 10 high power LEDs in series. The PAM2842 supports buck, boost and sepic topology. The PAM2842 features over current , over voltage , under voltage lockout and over temperature protection, which prevent the device from damage. The PAM2842 is available in TSSOP-20 packages. � � � � � � � � � � � � Peak Efficiency up to 97% Switching Frequency Adjustable Support Buck/Boost/Sepic Topology 1 www.poweranalog.com ,Power Analog Microelectronics Inc Boost with Low Side Current Sense 09/2008 Rev 1.1 PAM2842 SWPGND PGND HVIN EN VDD-DR RT AGND SW OV VDD-5V COMP Sense+ Sense- Vin L1 PAM2842 SWPGND PGND HVIN EN VDD-DR RT AGND SW OV VDD-5V COMP Sense+ Sense- Vin Boost with High Side Current Sense 33 Hμ 430kΩ 15kΩ 0.14Ω 1k 10nFΩ 1 Fμ 10 Fμ 1 Fμ 1 Fμ 130kΩ 33 Hμ 430kΩ 15kΩ 1k 10nFΩ 1 Fμ 10 Fμ 1 Fμ 1 Fμ 130kΩ L1 0.14Ω Administrator Typewriter 深圳龙创威电子公司 PAM代理商 18123959495 董’R PAM2842 High Power LED Driver 2 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 Buck with High Side Current Sense Buck/Boost (Sepic) with High Side Current Sense Typical Application Circuit PAM2842 SWPGND PGND HVIN EN VDD-DR RT AGND SW OV VDD-5V COMP Sense+ Sense- Vin L Buck/Boost (Sepic) with Low Side Current Sense PAM2842 SWPGND PGND HVIN EN VDD-DR RT AGND SW OV VDD-5V COMP Sense+ Sense- Vin L1 L2 47 Hμ 220kΩ 12kΩ 1k 10nFΩ 1 Fμ 10 Fμ 1 Fμ 1 Fμ 130kΩ 47 Hμ 0.14Ω PAM2842 SWPGND PGND HVIN EN VDD-DR RT AGND SW OV VDD-5V COMP Sense+ Sense- Vin L2 L1 47 Hμ 220kΩ 12kΩ 1k 10nFΩ 1 Fμ 10 Fμ 1 Fμ 1 Fμ 130kΩ 47 Hμ 1k 100nFΩ 1nF 10 Fμ 1 Fμ 1 Fμ 130kΩ 0.14Ω NC 12kΩ 47 Hμ 10 Fμ 0.14Ω10 Fμ 56kΩ Block Diagram + GM - - PWM + Comparator OV SW PWM Logic And Driver + - PGND Adjustable Oscillator Shutdown And Soft-start Sense+ Σ Ramp Generator EN COMP CS RT 100mV Reference PGND SW HVIN LDO1 LDO2 VDD_5V VDD-DR AGND Sense- FB PAM2842 High Power LED Driver 3 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 Pin Configuration & Marking Information 4 X: Internal Code Y: Year WW: Week LL: Internal Code ,Power Analog Microelectronics Inc PAM2842 High Power LED Driver www.poweranalog.com Pin Number QFN 6x6-40 TSSOP-20 Name Description 1-6 1,2,3,4,10,11 PGND Power Ground 8 5 HVIN Input 9 6 EN Chip Enable, Active High 10 7 VDD-DR Internal LDO Output 12 8 RT Frequency Adjustment Pin 13 9 AGND Analog Ground 14 12 Sense- Sense resistor - 15 13 Sense+ Sense resistor + 17 14 COMP Compensation Node 21 15 VDD_5V Internal LDO Output 23 16 OV Over Voltage 25-30 17,18,19 SW Drain of Main Switch. 7,11,16,18-20,22,24,31-40 20 NC No Connect TOP View TSSOP-20 P A M 2 8 4 2 X X X Y W W L L 1 2 3 4 5 6 7 20 19 18 17 16 15 14 8 9 10 13 12 11 09/2008 Rev 1.1 Top View 6mm*6mm QFN 1 2 3 4 5 6 7 8 9 10 PGND PGND PGND PGND PGND PGND NC HVIN EN VDD-DR 13 14 15 16 17 18 19 20 A G N D S e n s e - S e n s e + N C C O M P N C N C N C 21 22 23 24 VDD_5V NC OV NC SW 25 26 27 28 29 30 313233343536 SW SW SW SW SW N C N C N C N C N C N C 37383940 N C N C N C N C 1 1 1 2 N C R T PAM2842 XXXYWWLL PGND PGND PGND PGND PGNDPGND HVIN EN VDD-DR AGND Sense- Sense+ COMP RT VDD_5V NC OV SW SW SW Absolute Maximum Ratings These are stress ratings only and functional operation is not implied Exposure to absolute maximum ratings for prolonged time periods may affect device reliability All voltages are with respect to ground . . . Supply Voltage.............................................40V Output Current................................................1A I/O Pin Voltage Range.........GND-0.3V to V +0.3V Storage Temperature................ Maximum Junction Temperature..................150 C Soldering Temperature.......................300 C, 5secDD O O .....-40 C to 125 C O O Recommended Operating Conditions Supply Voltage Range.........................5.5V to 40V Operation Temperature Range..........-40 C to 85 C Junction Temperature Range......... C O O .-40 C to 150 O O Thermal Information 5 ,Power Analog Microelectronics Inc PAM2842 High Power LED Driver www.poweranalog.com Parameter Symbol Package Maximum Unit TSSOP 20Thermal Resistance (Junction to Case) θJC QFN 6mm*6mm 7.6* TSSOP 90Thermal Resistance (Junction to Ambient) θJA QFN 6mm*6mm 18.1* °C/W 09/2008 Rev 1.1 *The Exposed PAD must be soldered to a thermal land on the PCB. Electrical Characteristic V =V =24V, 1Wx10 LEDs, T =25°C, unless otherwise notedEN DD A . 6 ,Power Analog Microelectronics Inc PAM2842 High Power LED Driver www.poweranalog.com PARAMETER Conditions Min Typ Max Units Input Voltage Range 5.5 40 V ENA=high (no switching) 1 2 mA ENA =high (1M switching frequency) 6 mA ENA =high (500k switching frequency) 3 mA ENA =high (200k switching frequency) 1.6 mA Quiescent Current ENA =low 5 10 μA Feedback Voltage, Low Side VFB=VSENSE+ -AGND, VSENSE-=AGND 95 100 105 mV Feedback Voltage, High Side VFB=VSENSE+ - VSENSE- 95 100 105 mV LED Current Line Regulation IO=350mA 0.02 %/V LED Current Load Regulation 1.0 % LDO Stage VDD_5V No switching 4.5 5 5.5 V VDD_5V current_limit No switching 14 74 90 mA VDD_5V UVLO Threshold No switching 3.7 4.0 4.3 V VDD_5V UVLO Hysteresis No switching 200 mV VDD_DR No switching 4.5 5 5.5 V VDD_DR current_limit No switching 14 50 90 mA VDD_DR UVLO Threshold No switching 3.7 4.0 4.3 V VDD_DR UVLO Hysteresis No switching 200 mV Switch Stage Switch Rdson VDD_5V=5V 0.1 Ω Switch Current Limit 3.5 A Switch Leakage Current 50 μA RT Voltage RRT=71kΩ 1.1 1.2 1.3 V RRT=30kΩ 800k 1M 1.2M Hz RRT=71kΩ 400 500 600 kHzSwitching Frequency* RRT=180kΩ 160 200 240 kHz FSW=1MHz 10 % FSW=500kHz 5 %Min Duty Cycle FSW=200kHz 2.5 % Low Side Sense 95 % Max Duty Cycle High Side Sense 100 % Vc Source Current Feedback voltage=0 30 μA Vc Sink Current Feedback voltage=0 30 μA 09/2008 Rev 1.1 * Switching Frequency � � 12 10 24 12 SW RT F R k � � � , reference value 7 ,Power Analog Microelectronics Inc PAM2842 High Power LED Driver Electrical Characteristic V =V =24V, 1Wx10 LEDs, T =25 unless otherwise notedEN DD A , .°C www.poweranalog.com PARAMETER Conditions Min Typ Max Units Fault Protection OV threshold Voltage 1.1 1.2 1.3 V OV Hysteresis 70 mV Thermal-Shutdown 150 °C Thermal-Shutdown Hysteresis 30 °C Control Interface EN High 1.5 V EN Low 0.4 V 09/2008 Rev 1.1 8 ,Power Analog Microelectronics Inc PAM2842 High Power LED Driver Typical Performance Characteristic Boost mode, V =V =24V, 3W LED, Fsw=200kHz, T =25 unless otherwise notedEN DD A .°C, www.poweranalog.com 1. Input Voltage (Po=30W, 10X3W LEDs) Efficiency vs 2. Shutdown Current vs Input Voltage 3. Quiescent Current vs Input Voltage 09/2008 Rev 1.1 0 1 2 3 4 5 6 0 5 10 15 20 25 30 35 Input Voltage (V) S h u td o w n C u rr e n t (u A ) 93% 94% 95% 96% 97% 98% 10 15 20 25 30 Input Voltage (V) E ff ic ie n c y 4. Output Current vs Input Voltage (10X3W LEDs) 0 100 200 300 400 500 600 700 800 10 15 20 25 30 Input Voltage (V) O u tp u t C u rr e n t (m A ) Low side Current sense High side Current sense 0.6 0.8 1 1.2 1.4 1.6 1.8 0 5 10 15 20 25 30 35 Input Voltage (V) Q u ie s c e n t C u rr e n t (m A ) Switching No Switching 5. Output Current vs Temperature (V =12V, Load=10X3W LEDs)IN 400 450 500 550 600 650 700 750 800 0 20 40 60 80 100 Ambient Temperature (℃) O u tp u t C u rr e n t (m A ) PAM2842 High Power LED Driver Typical Performance Characteristic Fsw=300kHz, T =25°C, unless otherwise notedA . 9 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 0 50 100 150 200 250 300 350 400 0 20 40 60 80 100 Duty Cycle (%) L E D C u rr e n t (m A ) 9. LED Current vs Duty Cycle (PWM=100Hz, in Dimming State) 10. Start up and Shutdown 5. Output Current vs Input Voltage (Sepic mode, 1W LED), 6. Efficiency vs Input Voltage (Sepic mode, 1W LED), 0 50 100 150 200 250 300 350 400 5 10 15 20 Input Voltage (V) O u tp u t C u rr e n t (m A ) 5*1W 4*1W 3*1W 2*1W 1*1W 81% 82% 83% 84% 85% 86% 87% 88% 89% 90% 5 7 9 11 13 15 17 19 Input Voltage (V) E ff ic ie n c y 5*1W 4*1W 3*1W 2*1W 1*1W Vout EN Vcomp 70% 75% 80% 85% 90% 95% 100% 5 10 15 20 25 30 35 40 Input Voltage (V) E ff ic ie n c y 1*3W 2*3W 3*3W 8. Efficiency vs Input Voltage (Buck mode, 3W LED), 7. Output Current vs Input Voltage (Buck mode, 3W LED), 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 5 10 15 20 25 30 35 40 Input Voltage (V) O u tp u t C u rr e n t (A ) PAM2842 High Power LED Driver 10 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 Application Information Topology Selection Table-1: Voltage condition Vs Topology Inductor Selection When maximum power supply voltage is below than minimum load voltage, select the boost topology. When minimum power supply voltage is high than maximum load voltage, select buck topology. When load voltage range is small and between the power supply voltage, select sepic topology. The inductance, peak current rating, series resistance, and physical size should all be considered when selecting an inductor. These factors affect the converter's operating mode, eff iciency, maximum output load capabil i ty, transient response time, output voltage ripple, and cost. The maximum output current, input voltage, ou tpu t vo l t age , and sw i t ch ing f requency determine the inductor value. Large inductance can minimizes the current ripple, and therefore reduces the peak current, which decreases core losses in the inductor and I2R losses in the entire power path. However, large inductor values also require more energy storage and more turns of wire, which increases physical size and I2R copper losses in the inductor. Low inductor values decrease the physical size, but increase the current ripple and peak current. Finding the best inductor involves the compromises among circuit efficiency, inductor size, and cost. When choosing an inductor, the first step is to determine the operat ing mode: cont inuous conduct ion mode (CCM) or d iscont inuous conduction mode (DCM). When CCM mode is chosen, the ripple current and the peak current of the inductor can be minimized. If a small-size inductor is required, DCM mode can be chosen. In DCM mode, the inductor value and size can be minimized but the inductor ripple current and peak current are higher than those in CCM. For the large power application, if chose DCM, the peak current will be very large, it will have great electrical stress on the components, so we chose CCM. When work in CCM mode, a reasonable ripple current is chosen to I =0.4I For the boost topology, D: duty cycle, Io: output current, F: switching frequency. From above equation we can get the inductance: The inductor's current rating should be higher than For the buck topology, I =I so For the sepic topology, L1=L2 I =I Δ L L L O L2 O Condition Topology minmax VoVin � Boost maxmin VoVin � Buck VinVo � Sepic O L I I 1 D � � O IN O V V D V � � IN O IN L O V (V V ) I LFV � � � 2 IN O IN 2 O O 2.5V (V V ) L FI V � � L L I I 2 � � O IN V D V � IN O O L IN (V V )V I LFV � � � O IN O O IN 2.5V (V V ) L FI V � � L1 O D I I 1 D � � O IN O V D V V � � PAM2842 High Power LED Driver 11 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 Chose I =0.4I so An input capacitor is required to reduce the input ripple and noise for proper operation of the PAM2842. For good input decoupling, Low ESR (equivalent series resistance) capacitors should be used at the input. At least 10 F input capacitor is recommended for most applications. And close the IC Vin-Pin we should add a bypass capacitor, usually use a 1 F capacitor. A minimum output capacitor value of 10 F is r e c omme n d e d u n d e r n o rm a l o p e r a t i n g conditions, while a 22 F or higher capacitor may be required for higher power LED current. A reasonable value of the output capacitor depends on the LED current. The total output voltage ripple has two components: the capacitive ripple caused by the charging and discharging on the output capacitor, and the ohmic ripple due to the capacitor's equivalent series resistance. The ESR of the output capacitor is the important parameter to determine the output voltage ripple of the converter, so low ESR capacitors should be used at the output to reduce the output voltage ripple. T h e v o l t a g e r a t i n g a n d t e m p e r a t u r e characteristics of the Output capacitor must also be considered. So a value of 10 F, voltage rating capacitor is chosen. Consider from discharge aspect: Ix t=Cx V In boost and sepic topology, In buck topology, V : Output voltage allowable ripple. Consider from equivalent series resistance: V =I xC In sepic topology, there is a series capacitor Cs between L1 and L2 (see application schematic), it flows the current: The ripple voltage is The voltage rating must be higher than input voltage. Because the Cs capacitor will flow the large RMS current, so this topology is suitable for small power application. PAM2842 is a high switching frequency converter wh ich demands h igh speed rec t i f i e r. I t ' s indispensable to use a Schottky diode rated at 3A, 40V with the PAM2842. Using a Schottky diode with a lower forward voltage drop is better to improve the power LED efficiency. In boost topology, the voltage rating should be higher than Vout and in buck topology, the voltage rating higher than Vin, the peak current is in sepic topology, the voltage rating should be higher than Vin+Vout, the peak current is I =I +I The average current of the diode equals to Io. PAM2842 working frequency is decided by resistor connect to the RT pin, it can be calculated by follow equation: From the equations, we can see when working frequency is high, the inductance can be small. It's important in some size limit application. But we should know when the working frequency is higher, the switching loss is higher too. We must pay attention to thermal dissipation in this application. There are two methods for setting and adjusting the LED current: 1) Rsense only 2) PWM signal with external components a) Use the COMP pin b) Use the Sense pin Δ μ μ μ μ μ Δ Δ L L1 RIPPLE ripple-esr co.ripple oesr DMAX L1peak L2peak Capacitor Selection Diode Selection Work frequency selection Methods for Setting LED Current 50V IN O L IN O V V I LF(V V ) � � � 2 IN O IN O 2.5V L FI (V V ) � � O O RIPPLE I D C FV � O O RIPPLE I (1 D) C FV � � O Cs(RMS) O IN V I I V � O Cs S I D V FC � � L DMAX L I I I 2 � � � 12 SW 10 F (Hz) 24 (RT 12K) � � � Q1 2N7002 COMP PAM2842 PWM signal Ton Toff PAM2842 High Power LED Driver 12 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 � � � Method 1: LED Current Setting with Resistor Rsense Method 2: LED Current Setting with PWM Signal Using COMP Pin Figure 1. PWM Dimming Use COMP Pin Method 3: LED Current Setting with PWM Signal using Sense Pin Figure 2. PWM Dimming Use Sense Pin in Low Side Current Sense Figure 3. PWM Dimming Use Sense Pin in High Side Current Sense The most basic means of setting the LED current is connecting a resistor between Rsense+ and Rsense-. The LED current is decided by ISET Resistor Rsense. I =0.1/ R For flowing the large current, must pay attention to power dissipation on the resistor. Rsense has two position to select: high side current sense and low side current sense. In buck topology it just has high side current sense. In other topology we recommend use low side current sense for easier PCB layout. This circuit uses resistor Rsense to set the on state current and the average LED current, then proportional to the percentage of off-time when the COMP pin is logic high. Here use a invert component 2N7002 (Q1) to isolate and invert the PWM signal (See Figure 1). Average LED current is approximately equal to: Also, the recommended PWM frequency is between 100Hz and 200Hz. Frequency <100Hz can cause the LEDs to blink visibly. As the COMP pin connects to a capacitor, it needs rise time. If frequency >200Hz, the average LED current will have a large error when duty cycle is small (<50%). It maybe generate the audible noise in this dimming condition. This method is turn PWM signal to DC voltage, the output current can be adjusted. Because the LED current is a adjustable DC value, it will cause LED color drift. Low side current sense and high side current sense circuit is different. Please see Figure 2 and 3. It use the internal reference voltage, so PWM dimming signal voltage is not considered, just meet the request of the MOSFET driving voltage. The RC filter (R1,R2,C1,C2) value is decided by dimming frequency, the divider resistor (R3,R4) is decided by dimming range. Because final adjusted is a DC value, this method can avoid audible noise effectively and achieve better EMI performance than the second method. LED sense OFF LED AVG ON OFF T I I T T � � R1 R2 R3 R4 C1 C2 D1 Q1 RSense VDD_5V Sense+ RTN PWM-DIM R1 R3 R4C1 D1 Q1 RSense VDD_5V Sense- Vo PWM-DIM R5 Sense+ Q2 PAM2842 High Power LED Driver 13 ,Power Analog Microelectronics Inc www.poweranalog.com 09/2008 Rev 1.1 Setting the Output Limit Voltage Figure 5: Use External Zener Short LED Function Power Dissipation The OV pin is connected to the center tap of a resistive voltage divider from the high-voltage output to ground (see application schematic). The recommend procedure is to choose R3 =360K and R4 =12K to set Vout_limit =37.2V. In boost and sepic circuit, when LED open or no load, the circuit will have no feedback, if no other measure be taken the switch voltage will be very high and damage the switch, so this OV pin must be set carefully. In buck circuit, the switch voltage is always small than input voltage, so the OV pin setting is not important in this condition. This OV pin is used to limit output voltage to avoid breakdown of the switch other than to regulate output voltage. The setting value must keep the switch voltage below 40V. In sepic circuit, one must notice that the switch voltage equals Vin+Vo. This OV pin has a hysteresis voltage detect function, not latch-up function, so output voltage will have a overshoot when no load or load working voltage is high than setting limit voltage. I f t h e componen t pa r ame t e r no t ma t c h appropriately, the overshoot voltage will be too high and can demage the switch. Several methods can decrease the overshoot voltage: (1) Add a small capacitor (<100pF) parallel with the up divider resistor (See Figure 4). (2) Use external zener to clamp the output peak voltage (See Figure 5). Note: The output limit voltage must be set higher than working output voltage by a proper value, or it will work abnormal in low temperature or some other conditions. PAM2842 is a constant current driver. When one or more LED shorted, the circuit will still work, the output voltage is decided by LED num