AL8807BQ DIODES | Alldatasheet
Document overview
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Technical content
Features
LED driving current up to 1.3A Better than 5% accuracy High efficiency up to 96% Optimally controlled switching speeds Operating input voltage from 6V to 30V PWM input for dimming control Open-Circuit LED protection LED Chain Short Circuited Over-Temperature Protection MSOP-8EP Available in “Green” Molding Compound (No Br, Sb) with lead Free Finish/ RoHS Compliant Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. “Green” Device (Note 3) Automotive Grade Qualified to AEC-Q100 Standards for High Reliability PPAP Capable (Note 4) Pin Assignments
Applications
Automotive Lamps Notes: 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 bromi ne, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. 4. Automotive products are AEC-Q100 qualified and are PPAP capable. Automotive, AEC -Q100 and standard products are electrically and thermally the same, except where specified. For more information, please refer to http://www.diodes.com/quality/product_compliance_definitions/. Typical Application Circuit (Top View) MSOP-8EP SET GND GND CTRL VIN N/C SW SW
Document number: DS37011 Rev. 1 - 2 2 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Pin Descriptions Pin Name Pin Number Function SET 1 Set Nominal Output Current Pin. Configure the output current of the device. GND 2, 3 GND Pins CTRL 4 Dimming and On/Off Control Input. Leave floating for normal operation. (VCTRL = VREF = 2.5V giving nominal average output current IOUTnom = 0.1/RS) Drive to voltage below 0.4V to turn off output current A PWM signal ( 2.5V) allows the output current to be adjusted below the level set by the resistor connected to SET input pin. SW 5, 6 Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI. N/C 7 no connection VIN 8 Input Supply Pin. Must be locally decoupled to GND with > 2.2µF X7R ceramic capacitor – see applications section for more information. EP EP Exposed pad/TAB connects to GND and thermal mass for enhanced thermal impedance. Should not be used as electrical ground conduction path. Functional Block Diagram
Document number: DS37011 Rev. 1 - 2 3 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Absolute Maximum Ratings Symbol Parameter Ratings Unit ESD HBM Human Body Model ESD Protection 4 kV ESD MM Machine Model ESD Protection 300 V ESD CDM Charged Device Model ESD Protection 1000 V VIN Continuous VIN Pin Voltage Relative to GND -0.3 to +40 V VSW SW Voltage Relative to GND -0.3 to +40 V VCTRL CTRL Pin Input Voltage -0.3 to +6 V ISW-RMS DC or RMS Switch Current MSOP-8EP 1.6 A ISW-PK Peak Switch Current (<10%) 2.5 A TJ Junction Temperature +150 °C TLEAD Lead Temperature Soldering +300 °C TST Storage Temperature Range -65 to +150 °C Caution: Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are str ess ratings only; functional operation of the device at these or any other conditions exceeding those indicated in this specification is not im plied. 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. 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 Symbol Parameter Min Max Unit VIN Operating Input Voltage Relative to GND 6.0 30 V VCTRLH Voltage High for PWM Dimming Relative to GND 2.5 5.5 V VCTRLL Voltage Low for PWM Dimming Relative to GND 0 0.4 V fSW Maximum Switching Frequency — 1 MHz ISW Continuous Switch Current — 1.3 A TJ Junction Temperature Range -40 +125 °C Electrical Characteristics (VIN = 12V, @TA = +25°C, unless otherwise specified.) Symbol Parameter Conditions Min Typ Max Unit VINSU Internal Regulator Start Up Threshold VIN rising — — 5.9 V VINSH Internal Regulator Hysteresis Threshold VIN falling 100 — 300 mV IQ Quiescent Current Output not switching (Note 5) — — 350 µA IS Input Supply Current CTRL pin floating f = 250kHz — 1.8 5 mA VTH Set Current Threshold Voltage — 95 100 105 mV VTH-H Set Threshold Hysteresis — — ±15 — mV ISET SET Pin Input Current VSET = VIN-0.1 — 16 22 µA RCTRL CTRL Pin Input Resistance Referred to internal reference — 50 — kΩ VREF Internal Reference Voltage — 2.5 — V RDS(ON) On Resistance of SW MOSFET ISW = 1A — 0.25 0.4 Ω tR SW Rise Time VSENSE = 100 ±20mV fSW = 250kHz VSW = 0.1V~12V~0.1V CL = 15pF — 12 — ns tF SW Fall Time — 20 — ns TOTP Over-Temperature Shutdown — — 155 — C TOTP-Hyst Over-Temperature Hysteresis — — 55 — C ISW_Leakage Switch Leakage Current VIN =30V — — 0.5 μA θJA Thermal Resistance Junction-to- Ambient (Note 6) (Note 7) — 69 — C/W θJC Thermal Resistance Junction-to-case (Note 8) (Note 7) — 4.3 — — Notes: 5. AL8807BQ does not have a low power standby mode but current consumption is reduced when output switch is inhibited: V SENSE = 0V. Parameter is tested with VCTRL ≤ 2.5V. 6. Refer to figure 39 for the device derating curve. 7. Test condition for MSOP-8EP: Device mounted on FR-4 PCB (51mm x 51mm 2oz copper, minimum recommended pad layout on top layer and thermal vias to bottom layer with maximum area groun d plane. For better thermal performance, larger copper pad for heat -sink is needed. 8. Dominant conduction path is via exposed pad.
Figure 1. Supply Current (notswitching vs. Input Voltage Figure 6. V VS. TEMPERATURECTRL
2.48 V (V)CTRL
Figure 9. SW R vs. Temperature
Document number: DS37011 Rev. 1 - 2 9 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ
Application Information
The AL8807BQ is a hysteretic (also known as equal ripple) LED driver with integrated power switch. It is available in two packages that pr ovide a PCB area-power dissipation capability compromise. It is recommended that at higher LED currents/smaller PCBs that the MSOP -8EP version is used to maximize the allowable LED current over a wider ambient temperature range. AL8807BQ Operation In normal operation, when voltage is applied at +V IN, the AL8807BQ internal switch is turned on. Current starts to flow through sense resistor R 1, inductor L1, and the LEDs. The current ramps up linearly, and the ramp rate is determined by the input voltage +Vin and the inductor L1. This rising current produces a volta ge ramp across R 1. The internal circuit of the AL8807BQ senses the voltage across R 1 and applies a proportional voltage to the input of the internal comparator. When this voltage reaches an internally set upper threshold, the internal switch is turned off. The inductor current continues to flow through R1, L1, the LEDs and the schottky diode D1, and back to the supply rail, but it decays, with the rate of decay determined by the forw ard voltage drop of the LEDs and the schottky diode. This decaying current produces a falling voltage at R1, which is sensed by the AL8807BQ. A voltage proportional to the sense voltage across R1 is applied at the input of the internal comparator. When this voltage falls to the internally set lower threshold, the internal switch is turned on again. This switch-on-and-off cycle continues to provide the average LED current set by the sense resistor R1. LED Current Control The LED current is controlled by the resistor R1 in Figure 31. Figure 31 Typical Application Circuit Figure 32 Typical Operating Waveform (C2 not fitted) Connected between VIN and SET the nominal average output current in the LED(s) is defined as: VI THD LED For example for a desired LED current of 660mA and a default voltage VCTRL=2.5V the resulting resistor is: m15066.0 1.0 I V1R LED THD VIN = 12V TA =25ºC
2 LEDs
Ch2: 2V/div Ch4: 100mA/div Ch4: LED Current Ch2: SW Pin
Document number: DS37011 Rev. 1 - 2 12 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Applications Information (cont.) Reducing Output Ripple Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor C2 across the LED(s) as shown already in the circuit schematic. A value of 1μF will reduce the supply ripple current by a factor three (approx.). Proportionally lower ripple can be achieved with higher capacitor values. Note that the capacitor will not affect operating frequency or efficiency, but it will increase start -up delay, by reducing the rate of rise of LED voltage. By adding this capacitor the current waveform through the LED(s) changes from a triangular ramp to a more sinuso idal version without altering the mean current value. Capacitor Selection The small size of ceramic capacitors makes them ideal for AL8807BQ applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Z5U. A 2.2μF input capacitor is sufficient for most intended applications of AL8807BQ; however a 4.7μF input capacitor is suggested for input voltages approaching 30V. Diode Selection For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode with low reverse leakage at the maximum operating voltage and temperature. The Schottky diode also provides better efficiency than silicon PN diodes, due to a combination of lower forward voltage and reduced recovery time. It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum output load current. In particular, it is recommended to have a diode voltage rating at least 15% higher than the operating voltage to ensure safe operation during the switching and a current rating at least 10% higher than the average diode current. The power rating is verified by calculating the power loss through the diode. Schottky diodes, e.g. B240 or B140, with their low forward voltage drop and fast reverse recovery, are the ideal choice for AL8807BQ applications. Inductor Selection As the AL8807B is a hysteretic converter the switching frequency is depende nt on inductor value and the potential difference between the LED chain voltage and input voltage. Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in increased ripple a nd lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range (See graphs). Based on this r ecommended inductor values for the AL8807BQ are in the range 33μH to 100μH. To allow higher PWM dimming frequencies larger switching frequencies (see PWM dimming section) are required which necessitates the use smaller inductor values (for example down to 4.7µH). Figure 37 Inductor value with input voltage and number of LEDs The inductor should be mounted as close to the device as possible with low resistance/stray inductance connections to the SW pin.
Document number: DS37011 Rev. 1 - 2 13 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Applications Information (cont.) Inductor Selection (cont.) The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean output current. Suitable coils for use with the AL8807BQ are listed in the table below: Part No. L (µH) DCR (V) ISAT (A) Manufacturer NPIS64D330MTRF 33 0.124 1.1 NIC www.niccomp.com The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times over the supply voltage and load current range. The following equations can be used as a guide, with reference to Figure 38 – typical switching waveforms. Switch ‘On’ time RrRxIVV ILt SWLSAVGLEDIN ON Switch ‘Off’ time rRxIVV ILt LSAVGDLED OFF Where: L is the coil inductance (H) rL is the coil resistance (Ω) RS is the current sense resistance (Ω) Iavg is the required LED current (A) ΔI is the coil peak-peak ripple current (A) {Internally set to 0.3 x Iavg} VIN is the supply voltage (V) Figure 38 Typical Switching Waveform VLED is the total LED forward voltage (V) RSW is the switch resistance (Ω) {=0.5Ω nominal} VD is the diode forward voltage at the required load current (V) Thermal Protection The AL8807BQ includes Over-Temperature Protection (OTP) circuitry that will turn off the device if its junction temperature gets too high. This is to protect the device from excessive heat damage. The OTP circuitry includes thermal hysteresis that will cause the devic e to restart normal operation once its junction temperature has cooled down by approximately 55°C. Thermal Considerations For continuous conduction mode of operation, the absolute maximum junction temperature must not be exceeded. The maximum powe r dissipation depends on several factors: the thermal resistance of the IC package JA, PCB layout, airflow surrounding the IC, and difference between junction and ambient temperature. The maximum power dissipation can be calculated using the following formula: PD(MAX) = (TJ(MAX) − TA) / JA where TJ(MAX) is the maximum operating junction temperature Maximum recommended = 125°C TA is the ambient temperature, and JA is the junction to ambient thermal resistance. JA, is layout dependent and package dependent; the AL8807BQ’s JA on a n FR4 51x51mm PCB with 2oz copper standing in still air is approximately 69°C/W. So the maximum power dissipation at TA = +25°C is: PD(MAX) = (125°C − 25°C) / (69°C/W) = 1.41W for the above dimensioned PCB VIN = 12V TA =25ºC SW Pin: 2V/div On Off
Document number: DS37011 Rev. 1 - 2 15 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Applications Information (cont.) EMI and Layout Considerations The AL8807BQ is a switching regulator with fast edges and measures small differential voltages; as a result of this care has to be taken w ith decoupling and layout of the PCB.To help with these effects the AL8807BQ has been developed to minimise radiated emissions by controlling the switching speeds of the internal power MOSFET. The rise and fall times are controlled to get the right compromise between po wer dissipation due to switching losses and radiated EMI. The turn-on edge (falling edge) dominates the radiated EMI which is due to an interaction between the Schottky diode (D1), Switching MOSFET and PCB tracks. After the Schottky diode reverse recovery time of around 5ns has occur red; the falling edge of the SW pin sees a resonant loop between the Schottky diode capacitance and the track inductance, LTRACK, See Figure 41. The tracks from the SW pin to the Anode of the Schottky diode, D1, and then from D1’s cathode to the decoupling capacitors C1 should be as short as possible. There is an inductance internally in the AL8807BQ this can be assumed to be around 1nH. For PCB tracks a figure of 0.5nH per mm can be used to estimate the primary resonant frequency. If the track is capable of handling 1A increasing the thickness will have a minor effect on the inductance and length will dominate the size of the inductance. The resonant frequency of any oscillation is d etermined by the combined inductance in the track and the effective capacitance of the Schottky diode. Figure 41 PCB Loop Resonance Recommendations for minimising radiated EMI and other transients and thermal considerations are: 1. The decoupling capacitor (C1) has to be placed as close as possible to the VIN pin and D1 Cathode 2. The freewheeling diode’s (D1) anode, the SW pin and the inductor have to be placed as close as possible to each other to avoid ringing. 3. The Ground return path from C1 must be a low impedance path with the ground plane as large as possible 4. The LED current sense resistor (R1) has to be placed as close as possible to the VIN and SET pins. 5. The majority of the conducted heat from the AL8807BQ is through the exposed pad underneath the MSOP -EP package. A maximum earth plane with thermal vias into a second earth plane will minimise self-heating 6. To reduce emissions via long leads on the supply input and LEDs low RF impedance capacitors (C2 and C5) should be used at the point the wires are joined to the PCB
Document number: DS37011 Rev. 1 - 2 16 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Applications Information (cont.) Fault Condition Operation Open Circuit LEDs The AL8807BQ has by default open LED protection. If the LEDs should become open circuit the AL8807BQ will stop oscillating; the SET pin will rise to VIN and the SW pin will then fall to GND. No excessive voltages will be seen by the AL8807BQ. LED Chain Shorted Together If the LED chain should become shorted together (the anode of the top LED becomes shorted to the cathode of the bottom LED) t he AL8807BQ will continue to switch and the current through the AL8807BQ’s internal switch will still be at the expected current - so no excessive heat will be generated within the AL8807BQ. However, the duty cycle at which it operates will change dramatically and the switching frequency will most likely decrease. See Figure 43 for an example of this behavior at 24V input voltage driving 3 LEDs. The on-time of the internal power MOSFET switch is significantly reduced because almost all of the input voltage is now dev eloped across the inductor. The off-time is significantly increased because the reverse voltage across the inductor is now just the Schottky diode voltage (See Figure 43) causing a much slower decay in inductor current. Figure 43 Switching Characteristics (normal operation to LED chain shorted out) High Temperature Operation and Protection The AL8807BQ is a high efficiency switching LED driver capable of operating junction temperatures up to +125°C . This allows it operate with ambient temperature in excess of 100°C given the correct thermal impedance to free air. If a fault should occur that leads to increased ambient temperatures and hence junction temperature then the Over -Temperature Protection (OTP) of the AL8807BQ will cut-in, turning the output of the AL8807BQ off. This will allow the junction temperature of the AL8807BQ to cool down and potentially giving an opportunity for the fault to clear itself. The OTP shutdown junction temperature of the AL8807BQ is approximately +155°C with a hysteresis of +55°C. This means that the AL8807BQ will never switch -off with a junction temperature below +125°C allowing the designer to design the system thermally to fully utilize the wide operating junction temperature of the AL8807BQ.
Document number: DS37011 Rev. 1 - 2 17 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ
Ordering Information
Part Number Package Code Packaging (Note 9) Packing: 13” Tape and Reel Qualification Grade (Note 10) Quantity Tape Width Part Number Suffix AL8807BQMP-13 MP MSOP-8EP 2500 12mm -13 Automotive Grade Note: 9. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf 10. AL8807BQ have been qualified to AEC-Q100 grade 1 and is classified as “Automotive Grade” which supports PPAP documentation. See AL8807B datasheet for commercial qualified versions. Marking Information (1) MSOP-8EP Part Number Package AL8807BQMP-13 MSOP-8EP Package Outline Dimensions (All dimensions in mm.) Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version. MSOP-8EP 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 D1 1.60 2.00 1.80 E 4.70 5.10 4.90 E1 2.90 3.10 3.00 E2 1.30 1.70 1.50 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 D A E e y x Seating Plane Gauge Plane L D 8Xb See Detail C Detail C c a 4X10° 4X10° 0.25D1
Document number: DS37011 Rev. 1 - 2 18 of 18 www.diodes.com October 2014 © Diodes Incorporated NEW PRODUCT AL8807BQ Suggested Pad Layout Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. 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). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any lia bility arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license unde r its patent or trademark rights, nor the rights of others. Any Customer or user of this document or pro ducts described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diod es Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising ou t of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product nam es and markings noted herein may also be covered by one or more United States, international or foreign trademarks. This document is written in English but may be translated into multiple languages for reference. Only the English version of t his document is the final and determinative format released by Diodes Incorporated. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided i n the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support d evices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety -critical, life support devices or systems, notwithstanding any devices - or systems -related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2014, Diodes Incorporated www.diodes.com Dimensions Value (in mm) C 0.650 G 0.450 X 0.450 X1 2.000 Y 1.350 Y1 1.700 Y2 5.300 G X C Y Y2 Y1