AL8811 Boost/Buck/Inverting DC-DC CONVERTER Description Pin Assignments The AL8811 is a monolithic control circuit containing the primary functions required for DC-to-DC converters. These devices consist of an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active current limit circuit, driver and high current output switch. This series is specifically designed for incorporating in Boost, Buck and voltage-inverting applications with a minimum number of external components. Features Operation from 3.0V to 20V Input Low Standby Current Current Limiting Output Switch Current to 1.6A Output Voltage Adjustable Frequency Operation to 100 kHz Precision 2% Reference MSOP-8 Applications Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. “Green” Device (Note 3) Notes: Low Voltage LED Lighting such as MR-16 General Purpose DC-DC Converter 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. 2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free. 3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. Typical Application Diagram Electronic Transformer compatible MR16 lamp Simplified Schematic AL8811 Document number: DS36090 Rev. 2 - 2 1 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Pin Descriptions Pin Name Pin Number Current Switch+ 1 Current Switch- 2 CT GND Feedback VCC Current Sense Current Drive 3 4 5 6 7 8 Descriptions Internal switch transistor collector: Connect to Inductor for boost converter. Connect to VCC for Buck or Inverting converter Internal switch transistor emitter: Connect to GND for boost converter Connect to Inductor for buck or inverting converter Timing Capacitor to control the switching frequency Feedback pin for inverting input of internal comparator Supply voltage pin Peak Current Sense Input by monitoring the voltage drop across an external current sense resistor to limit the peak current through the switch Current drive collector: Normally connected to VCC directly or via a resistor. Functional Diagram AL8811 Document number: DS36090 Rev. 2 - 2 2 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) Symbol Parameter VCC Power Supply Voltage VIR Comparator Input Voltage Range Rating 20 Unit V -0.3 to +36 V VC (SWITCH) “Current Switch +” Collector Voltage 36 V VE (SWITCH) „Current Switch –„ Emitter Voltage (VPIN 1 = 36V) 36 V VCE (SWITCH) V “Current Switch” Collector to Emitter Voltage 36 VC (DRIVER) “Current Drive” Collector Voltage 36 V IC (DRIVER) “Current Drive” Collector Current 100 mA “Current Switch” Current 1.6 A PD Power Dissipation (Note 4) 600 mW JA Thermal Resistance 130 C/W +150 C ISW TMJ Maximum Junction Temperature TSTG Storage Temperature Range ESD HBM ESD MM Caution: Human Body Model ESD Protection Machine Model ESD Protection -65 to +150 C 1 150 kV V Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only; functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling and transporting these devices. Recommended Operating Conditions Parameter Min Max Unit Supply Voltage Operating Junction Temperature Range 3 -40 20 +105 V C Symbol VCC TOP Electrical Characteristics (@ VCC = 5V, TA = +25°C, unless otherwise specified.) Symbol OSCILLATOR Parameter Min Typ Max Unit kHz fOSC Frequency (VPIN 5 = 0V, CT = 1.0nF, TA = +25°C) 24 33 42 ICHG Charge Current (VCC = 5.0V to 20V, TA = +25°C) 24 30 42 µA Discharge Current (VCC = 5.0V to 20V, TA = +25°C) 140 200 260 µA IDISCHG IDISCHG/ ICHG Discharge to Charge Current Ratio (Pin 7 to VCC, TA = +25°C) 5.2 6.5 7.5 — VIPK (SENSE) Current Limit Sense Voltage (ICHG = IDISCHG, TA = +25°C) 300 400 450 mV — 1.0 1.3 V Saturation Voltage, Darlington Connection (ISW = 1.0A, ID = 50mA, Forced ß 20) — 0.45 0.7 V DC Current Gain (ISW = 1.0A, VCE = 5.0V, TA = +25°C) 50 75 — — Collector Off-State Current (VCE = 20V) — 0.01 100 µA 1.225 1.25 1.275 V Threshold Voltage Line Regulation (VCC = 3.0V to 20V) — 1.4 6.0 mV Supply Current (VCC = 5.0V to 20V, CT =1.0nF, Pin 7 = VCC, VPIN 5 > Vth Pin 2 = Gnd, remaining pins open) — — 3.5 mA OUTPUT SWITCH (Note 4) Saturation Voltage, Darlington Connection VCE(sat) (ISW = 1.0A, Pins 1, 8 connected) VCE(sat) hFE IC(off) COMPARATOR Vth Reg(LINE) Threshold Voltage TA = +25°C TOTAL DEVICE ICC AL8811 Document number: DS36090 Rev. 2 - 2 3 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Typical Performance Characteristics Figure 1. Vce(sat) versus le Figure 2. Reference Voltage versus Temp. 1.26 Reference Voltage (V) Vce(sat), Saturation Voltage (V) 1.4 1.2 1 0.8 0.6 1.255 1.25 1.245 1.24 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 10 20 30 Ie, Emitter Current (A) Figure 3. Current Limit Sense Voltage versus Temperature Icc, Supply Current (mA) Current Sense Voltage (mV) 400 380 360 340 20 30 40 50 60 70 80 90 100 3.0 2.5 2.0 1.5 1.0 100 0 5 10 15 20 25 30 35 40 Vcc, Supply Voltage (V) Figure 6.Output Switch On-Off Time versus Oscillator Timing Capacitor 1000 ton-off, Output Switch On-Off Time(us) VCE ( sat), (V) 90 3.5 (oC) 1.8 Vcc=2~10V Pin1,7,8=Vcc Pin3,5=GND TA=25oC Pin2=5 10W 1.6 1.55 1.5 1.45 1.4 100 80 0.0 10 Figure 5. Emitter Follower Configuration Output Saturation Voltage vs. Emitter Current 1.65 70 0.5 Temperature 1.7 60 4.0 420 1.75 50 Figure 4. Standby Supply Current versus Supply Voltage 440 320 0 40 Temperature (oC) 300 500 AL8811 Document number: DS36090 Rev. 2 - 2 700 900 IE(mA) 1100 1300 1500 100 VCC = 5.0V Pin 7 = VCC Pin 5 = GND TA = 25oC ton 10 t off 1 0.1 0.01 4 of 11 www.diodes.com 0.1 1 CT, Oscillator Timing Capacitor ( nF) 10 June 2013 © Diodes Incorporated AL8811 Application Circuit (1) Boost Converter Test Conditions Results Line Regulation VIN = 9V to 12V, IO = 200mA 20mV = ±0.035% Load Regulation VIN = 12V, IO = 50mA to 200mA 15mV = ±0.035% Output Ripple VIN = 12V, IO = 200mA 500mVPP Efficiency VIN = 12V, IO = 200mA 80% AL8811 Document number: DS36090 Rev. 2 - 2 5 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Application Circuit (cont.) (2) Electronic Transformer compatible triac dimmable MR16/GU5.3 lamp for 120Vac Circuit Description This design consists of three sections: 1) The input PFC circuit converts the 12VAC input voltage to a DC voltage around 30V (AL8811). 2) The output Buck LED Driver drives the three LEDs in series at a fixed current (AL8807A). 3) Finally, the phase-detect circuit generates a voltage proportional to the phase of the incoming AC voltage (when triac dimming is used). PFC Circuit The AL8811 Boost converter is a simple “Constant ON time controller”. By keeping the same ON time throughout the AC cycle, the circuit will draw a current that will closely match the voltage and result in a constant input current. This eliminates the classic peak current problem with a bridge rectifier and a large input filter capacitor. The PFC circuit includes the input bridge rectifier, EMI filter (if needed) and the AL8811 Boost converter. The AC input voltage is rectified by the bridge circuit and filtered by C1, R1, C4, and C5. This first filter removes the high frequency that is generated by the Electronic Transformer in the range of 20-30 KHz. An additional diode rectifier circuit (D5, C2) is used to generate a voltage that is used to power the circuit that will turn on/off the external MOSFET of the Boost converter. This circuit is very important as the gate drive of the MOSFET has to be greater than 3-4 volts throughout the AC cycle. The external MOSFET is used to reduce the heat dissipation in the AL8811. The AL8811 has a current limit resistor R3 which sets the maximum current allowed through the inductor L1. The output voltage is set by the divider R6, R5 to an output of around 35 volts. The output voltage is filtered by the two capacitors C8 and C9. These two capacitors store energy that will be used when the input voltage is low during the AC cycle. AL8811 Document number: DS36090 Rev. 2 - 2 6 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Application Circuit (cont.) Buck LED Driver The AL8807A is a step-down DC-DC converter designed to drive LEDs with a constant current. The current through the LED is controlled by R11. In the present Evaluation board, the current is set to around 660mA based on a resistor value of 0.15Ω. The current is set using the “CTRL” input pin which in this new version of the IC can vary from 0 to 2.5V, controlling the current from 0mA to the maximum current at 2.5V. This control input pin is used to lower the LED current as the TRIAC dims the LED. In this way, the energy stored in the two output capacitors of the PFC circuit will be able to provide current throughout the AC cycle. TRIAC Phase Detection Circuit The phase of the TRIAC is detected by using an additional rectifier circuit that generates a voltage in proportional to the phase of the TRIAC Driver. This is done by rectifying the input AC voltage and averaging the energy using a resistor to charge a capacitor. Two additional resistors in series, R12 and R8, slowly discharge this circuit so it will follow the input phase change. The two resistors, R12 and R8, are used to scale the voltage so the range is from 0 to 2.6V to the Buck LED driver control pin. A simple transistor emitter follower circuit is used to drive a 1KΩ resistor in the emitter circuit. This low resistance is needed to drive the input control pin of the AL8807A LED driver because the pin outputs a small current of 50uA, which limits the lowest control voltage to around 50 mV. Setting the LED output current (AL8807A): The LED output current is set using resister R11 and the formula: ILED = VTH / R11 where VTH is equal to 0.1V For a current of 660mA, R11 is about 0.15Ω. Setting the PFC Variables (AL8811) The choice for the size of the boost converter inductor selected in this design is based on a compromise which it is able to support a peak current to around 1.5A since the average input voltage will be around 12-14V. The boost converter (AL8811) includes a current limit resistor R3 which will limit the current through the inductor and thus the power delivered to the output load. The formula for the resistor is: IPK(switch) = 0.33V / R3 For a current limit of 1A, R3 is 0.33Ω. In this evaluation design, this value was selected based on having three LEDs in series drawing about 660mA. It was found that two 68µF capacitors mounted in parallel would just fit into the cavity of the MR16 bulb. The important design goal is to have the PFC circuit, which is used to always draw current from the Electronic Transformer. AL8811 Document number: DS36090 Rev. 2 - 2 7 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Application Circuit (cont.) (3) Buck Converter Test Line Regulation VIN = 12V to 20V, IO = 500mA Conditions Results 20mV = ±0.2% Load Regulation VIN = 20V, IO = 50mA to 500mA 5mV = ±0.05% Output Ripple VIN = 20V, IO = 500mA 160mVPP Efficiency VIN = 20V, IO = 500mA 82% 1 8 Q2 Q1 Q S R 7 2 I pk CT B240 Rsc 0.11 Osc 3 100uH L VCC TC 470 pF 1.25V Ref Reg 1.0uH 100 + Vin 20 + Comp. + _ 4 V out 6 470 uF 5 Vout 5.0V/500mA R2 + CO 36k 470uF 25k R1 Optional Filter AL8811 Document number: DS36090 Rev. 2 - 2 8 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Application Circuit (cont.) (4) Voltage Inverting Converter Test Conditions Results Line Regulation Vin = 4.5V to 6.0V, IO = 100mA 20mV = ±0.08% Load Regulation Vin = 5.0V, IO = 20mA to 100mA 30mV = ±0.12% Output Ripple Vin = 5.0V, IO = 100mA 500mVPP Efficiency Vin = 5.0V, IO = 100mA 60% AL8811 Document number: DS36090 Rev. 2 - 2 9 of 11 www.diodes.com June 2013 © Diodes Incorporated AL8811 Ordering Information Part Number Package Code Packaging AL8811M8-13 M8 MSOP-8 Quantity NA Tube Part Number Suffix NA 13” Tape and Reel Quantity Part Number Suffix 2500/Tape & Reel -13 Marking Information (1) MSOP-8 ( Top View ) 8 7 6 Logo 5 YWX AL8811 Part Number 2 1 3 Internal Code Y : Year : 0~9 W : Week : A~Z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week 4 Package Outline Dimensions (All dimensions in mm.) Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version. D 4x 10 ° 0.25 E Gauge Plane x Seating Plane a y 4x10° L Detail C 1 b E3 A3 A2 A e A1 AL8811 Document number: DS36090 Rev. 2 - 2 E1 c See Detail C 10 of 11 www.diodes.com MSOP-8 Dim Min Max Typ A 1.10 A1 0.05 0.15 0.10 A2 0.75 0.95 0.86 A3 0.29 0.49 0.39 b 0.22 0.38 0.30 c 0.08 0.23 0.15 D 2.90 3.10 3.00 E 4.70 5.10 4.90 E1 2.90 3.10 3.00 E3 2.85 3.05 2.95 e 0.65 L 0.40 0.80 0.60 a 0° 8° 4° x 0.750 y 0.750 All Dimensions in mm June 2013 © Diodes Incorporated AL8811 Suggested Pad Layout Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. X C Y Dimensions Value (in mm) C 0.650 X 0.450 Y 1.350 Y1 5.300 Y1 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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