A Product Line of Diodes Incorporated ZXLD1366 HIGH ACCURACY 1A, 60V LED DRIVER WITH AEC-Q100 Description Pin Assignments The ZXLD1366 is a continuous mode inductive step-down (TOP VIEW) converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. LX 1 The device operates from an input supply between 6V and 60V and provides an externally adjustable output current of up to 1A. GND 2 The ZXLD1366 has been qualified to AECQ100 Grade 1 enabling operation in ambient temperatures from -40C to +125C 5 VIN 4 ISENSE ADJ 3 TSOT25 The ZXLD1366 uses a high-side output current sensing circuit which uses an external resistor to set the nominal average output (TOP VIEW) current. The output current can be adjusted above, or below the set value, by applying an external control signal to the 'ADJ' pin. LX 1 Enhanced output current dimming resolution can be achieved by applying a PWM signal to the `ADJ' pin. GND 2 5 GND ADJ 3 4 ISENSE Soft-start can be forced using an external capacitor from the ADJ pin to ground. Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and switches the device into a low current standby state. U-DFN3030-6 (TOP VIEW) Features * * * * * * * * * * 6 VIN Typically better than 0.8% output current accuracy Simple and with low part count Single pin on/off and brightness control using DC voltage or PWM PWM resolution up to 1000:1 High efficiency (up to 97%) Switching frequencies up to 1MHz Wide input voltage range: 6V to 60V Inherent open-circuit LED protection Available in thermally enhanced Green molding packages SO-8EP JA = +45C/W U- DFN3030-6 JA = +44C/W TSOT25 JA = +82C/W Totally Lead-free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. "Green" Device (Note 3) Qualified to AEC-Q100 Grade 1 SO-8EP ZXLD1366EN8TC TSOT25 ZXLD1366ET5TA LX 1 8 VIN GND 2 GND 3 6 GND ADJ 4 5 ISENSE 7 GND SO-8EP Typical Application Circuit D1 Rs VIN (24V) 0.2V Applications * * * * * * * L1 Automotive lighting Low voltage industrial lighting LED back-up lighting Illuminated signs Emergency lighting SELV lighting Refrigeration lights C1 4.7F 100nF VIN ISEN SE ADJ ZXLD1366 LX GND GND Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied. 2. See http://www.diodes.com 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. ZXLD1366 Document number: DS31992 Rev. 7 - 2 1 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Block Diagram D1 VIN L1 RS 5 5V C1 4.7F 4 VIN ISENSE 1 LX R1 Voltage regulator + 0.2V + Low voltage dete ctor MN + Adj 3 R4 50K R5 20K 600KHz R2 D1 1.25V + R3 1.35V Gnd 2 Figure. 1 Pin Connection for TSOT25 Package Pin Description Name TSOT25 U-DFN3030-6 SO-8EP LX 1 1 1 GND 2 2, 5 2, 3, 6, 7 Function Drain of NDMOS switch Ground (0V) Multi-function On/Off and brightness control pin: ADJ 3 3 4 * Leave floating for normal operation.(VADJ = VREF = 1.25V giving average output current IOUTnom = 0.2V/RS) * Drive to voltage below 0.2V to turn off output current * Drive with DC voltage (0.3V < VADJ < 2.5V) to adjust output current from 25% to 200% of IOUTnom * Connect a capacitor from this pin to ground to set soft-start time. nominal Soft start time increases approximately 0.2ms/nF ISENSE 4 4 5 Connect resistor RS from this pin to VIN to define nominal average output current IOUTnom = 0.2V/RS. (Note: RSMIN = 0.2V with ADJ pin open-circuit) VIN 5 6 8 Input Voltage (6V to 60V). Decouple to ground with 4.7F of higher X7R ceramic capacitor close to device. Exposed Pad (EP) - connected to device substrate. To improve thermal impedance of package the EP must be connected to power Pad - Pad Pad ground but should not be used as the 0V (GND) current path. It can be left floating but must not be connected to any other voltage other than 0V. ZXLD1366 Document number: DS31992 Rev. 7 - 2 2 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Absolute Maximum Ratings (Note 4) Symbol Rating Unit Input Voltage Parameter -0.3 to +65 V ISENSE Voltage (Note 5) +0.3 to -5 V VLX LX Output Voltage -0.3 to +65 V VADJ Adjust Pin Input Voltage -0.3 to +6 V 1.25 A VIN VSENSE ILX Switch Output Current Power Dissipation TSOT25 PTOT (Refer to Package thermal de-rating curve on page 25) U-DFN3030-6 TOP Operating Temperature -40 to +125 C TST Storage Temperature -55 to +150 C Junction Temperature +150 C TJ MAX 1 W 1.8 SO-8EP 2.2 Note: 4 All voltages unless otherwise stated are measured with respect to GND. 5. VSENSE is measured with respect to VIN. Caution: 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 conditions between maximum recommended operating conditions and absolute maximum ratings is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. ESD Susceptibility Rating Unit Human Body Model 500 V Machine Model 75 V Caution: 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. The human body model is a 100pF capacitor discharge through a 1.5k resistor pin. The machine model is a 200pF capacitor discharged directly into each pin. Thermal Resistance Symbol Parameter JA Rating TSOT25 SO-8EP U-DFN3030-6 Junction to Ambient 82 45 44 JB Junction to Board 33 -- -- JC Junction to Case -- 7 14 Unit C/W Recommended Operating Conditions Symbol Parameter VIN Input voltage (Note 6) ILX Maximum recommended continuous/RMS switch current VADJ Max 6 60 V 1 A 2.5 V DC voltage on ADJ pin to ensure devices is off 0.25 V tOFFMIN Minimum switch off-time 800 ns tONMIN Minimum switch on-time 800 ns fLX MAX Recommended maximum operating frequency (Note 8) 625 kHz Duty cycle range DLX(LIMIT) Recommended duty cycle range of output switch at fLXMAX TOP Notes: Operating Temperature range 0.3 Units VADJOFF DLX External control voltage range on ADJ pin for DC brightness control (Note 7) Min 0.01 0.99 0.3 0.7 -40 +125 C 6. VIN > 16V to fully enhance output transistor. Otherwise out current must be derated - see graphs. Operation at low supply may cause excessive heating due to increased on-resistance. Tested at 7V guaranteed for 6V by design. 7. 100% brightness corresponds to VADJ = VADJ(nom) = VREF. Driving the ADJ pin above VREF will increase the VSENSE threshold and output current proportionally. 8. ZXLD1366 will operate at higher frequencies but accuracy will be affected due to propagation delays. ZXLD1366 Document number: DS31992 Rev. 7 - 2 3 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Electrical Characteristics (Test conditions: VIN = 24V, TA = +25C, unless otherwise specified.) Symbol VSU VSD Parameter Condition Min Internal regulator start-up threshold Internal regulator shutdown threshold 4.40 Typ Max Unit 4.85 5.20 V 108 A 4.75 IINQoff Quiescent supply current with output off ADJ pin grounded 65 IINQon Quiescent supply current with output switching (Note 9) ADJ pin floating, L = 68H, 3 LEDs, f = 260kHz 1.6 Mean current sense threshold voltage (Defines LED current setting accuracy) Measured on ISENSE pin with respect to VIN VADJ = 1.25V; VIN = 18V VSENSE VSENSEHYS ISENSE VREF VREF/T VADJ VADJoff VADJon RADJ ILXmean Sense threshold hysteresis ISENSE pin input current Internal reference voltage Resistance between ADJ pin and VREF 4 ILX(leak) LX switch leakage current 0 < VADJ < VREF VADJ > VREF +100mV tSS Soft start time fLX Operating frequency (See graphs for more details) 10 A (Note 8) Time taken for output current to reach 90% of final value after voltage on ADJ pin has risen above 0.3V. Requires external capacitor 22nF. See graphs for more details ADJ pin floating L = 68H (0.2V) IOUT = 1A @ VLED = 3.6V Driving 3 LEDs % 50 ppm/C 2.5 V 0.15 0.20 0.27 V 0.20 0.25 0.30 V 30 10.4 50 14.2 65 18.0 k 1 A 0.50 0.75 5 A 1.000 V 0.001 1000:1 5:1 2 ms 260 kHz tONmin Minimum switch `ON' time LX switch `ON' 130 tOFFmin Minimum switch `OFF' time LX switch `OFF' 70 Notes: mV V 0.3 @ ILX = 1A PWM frequency < 300Hz PWM Duty cycle range of PWM signal applied to ADJ pin amplitude = VREF during low frequency PWM dimming mode Measured on ADJ pin Brightness control range DC Brightness control range 205 1.25 Continuous LX switch current LX switch `On' resistance DCADJ 200 mA 15 VSENSE = VIN -0.2 Measured on ADJ pin with pin floating Temperature coefficient of VREF External control voltage range on ADJ pin for DC brightness control (Note 7) DC voltage on ADJ pin to switch device from active VADJ falling (on) state to quiescent (off) state DC voltage on ADJ pin to switch device from VADJ rising quiescent (off) state to active (on) state RLX DPWM(LF) 195 V 9. Static current of device is approximately 700 A, see Graph, Page 16 10. 100% brightness corresponds to VADJ = VADJ(nom) = VREF. Driving the ADJ pin above VREF will increase the VSENSE threshold and output current proportionally. 11. Ratio of maximum brightness to minimum brightness before shutdown VREF = 1.25/0.3. VREF externally driven to 2.5V, ratio 10:1. ZXLD1366 Document number: DS31992 Rev. 7 - 2 4 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Device Description The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a self-oscillating continuous-mode buck converter. Device Operation (refer to Figure 1 - Block diagram and Figure 2 Operating waveforms). VIN LX voltage 0V Toff Ton VIN 230mV 170mV SENSE voltage 200mV VSENSEVSENSE+ IOUTnom +15% IOUTnom Coil current IOUTnom -15% 0V Comparator input voltage 0.15VADJ VADJ 0.15VADJ Comparator output 5V 0V Figure 2. Theoretical Operating Waveforms Operation can be best understood by assuming that the ADJ pin of the device is unconnected and the voltage on this pin (VADJ) appears directly at the (+) input of the comparator. When input voltage VIN is first applied, the initial current in L1 and RS is zero and there is no output from the current sense circuit. Under this condition, the (-) input to the comparator is at ground and its output is high. This turns MN on and switches the LX pin low, causing current to flow from VIN to ground, via RS, L1 and the LED(s). The current rises at a rate determined by VIN and L1 to produce a voltage ramp (VSENSE) across RS. The supply referred voltage VSENSE is forced across internal resistor R1 by the current sense circuit and produces a proportional current in internal resistors R2 and R3. This produces a ground referred rising voltage at the (-) input of the comparator. When this reaches the threshold voltage (VADJ), the comparator output switches low and MN turns off. The comparator output also drives another NMOS switch, which bypasses internal resistor R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of VADJ. ZXLD1366 Document number: DS31992 Rev. 7 - 2 When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to VIN. The current decays at a rate determined by the LED(s) and diode forward voltages to produce a falling voltage at the input of the comparator. When this voltage returns to VADJ, the comparator output switches high again. This cycle of events repeats, with the comparator input ramping between limits of VADJ 15%. Switching Thresholds With VADJ = VREF, the ratios of R1, R2 and R3 define an average VSENSE switching threshold of 200mV (measured on the ISENSE pin with respect to VIN). The average output current IOUTnom is then defined by this voltage and RS according to: IOUTnom = 200mV/RS Nominal ripple current is 30mV/RS 5 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Device Description (cont.) Actual operating waveforms VIN = 15V, RS = 0.2, L = 68H Normal operation. VIN = 30V, RS = 0.2, L = 68H Normal operation. Output Current (Ch 3) and LX voltage (Ch 2) Output Current (Ch 3) and LX voltage (Ch 2) VIN = 60V, RS = 0.2, L = 68H Normal operation. Output Current (Ch 3) and LX voltage (Ch 2) Adjusting Output Current Output Shutdown The device contains a low pass filter between the ADJ pin and the threshold comparator and an internal current limiting resistor (50k nom) between ADJ and the internal reference voltage. This allows the ADJ pin to be overdriven with either DC or pulse signals to change the VSENSE switching threshold and adjust the output current. The output of the low pass filter drives the shutdown circuit. When the input voltage to this circuit falls below the threshold (0.2V nom.), the internal regulator and the output switch are turned off. The voltage reference remains powered during shutdown to provide the bias current for the shutdown circuit. Quiescent supply current during shutdown is nominally 60A and switch leakage is below 5A. Details of the different modes of adjusting output current are given in the applications section. ZXLD1366 Document number: DS31992 Rev. 7 - 2 6 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions 1.100 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs OUTPUT CURRENT (A) 1.080 1.060 1.040 1.020 1.000 0.980 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Output Current, L = 68H 10 OUTPUT CURRENT DEVIATION (%) 8 6 4 2 0 -2 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs -4 -6 -8 -10 0 10 20 30 40 50 60 50 60 SUPPLY VOLTAGE (V) Output Current Deviation, L = 68H 100 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 0 10 20 30 40 SUPPLY VOLTAGE (V) Efficiency, L = 68H ZXLD1366 Document number: DS31992 Rev. 7 - 2 7 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 500 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs SWITCHING FREQUENCY (kHz) 450 400 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Switching Frequency, L = 68H 100 90 80 DUTY CYCLE (%) 70 60 50 40 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 30 20 10 0 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Duty Cycle, L = 68H ZXLD1366 Document number: DS31992 Rev. 7 - 2 8 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 1.100 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs OUTPUT CURRENT (A) 1.080 1.060 1.040 1.020 1.000 0.980 0.960 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Output Current, L = 100H 10 OUTPUT CURRENT DEVIATION (%) 8 6 4 2 0 -2 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs -4 -6 -8 -10 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Output Current Deviation, L = 100H 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Efficiency, L = 100H ZXLD1366 Document number: DS31992 Rev. 7 - 2 9 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 500 1 LED 3 LEDs 5 LEDs 7 LEDs SWITCHING FREQUENCY (kHz) 450 400 11 LEDs 13 LEDs 15 LEDs 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Switching Frequency, L = 100H 100 90 80 DUTY CYCLE (%) 70 60 50 40 30 1 LED 3 LEDs 5 LEDs 7 LEDs 20 10 0 0 11 LEDs 13 LEDs 15 LEDs 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Duty Cycle, L = 100H ZXLD1366 Document number: DS31992 Rev. 7 - 2 10 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 1.100 OUTPUT CURRENT (A) 1.080 1.060 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 1.040 1.020 1.000 0.980 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Output Current, L = 150H 10 OUTPUT CURRENT DEVIATION (%) 8 6 4 2 0 -2 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs -4 -6 -8 -10 0 10 20 30 40 50 60 50 60 SUPPLY VOLTAGE (V) Output Current Deviation, L = 150H 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 0 10 20 30 40 SUPPLY VOLTAGE (V) Efficiency, L = 150H ZXLD1366 Document number: DS31992 Rev. 7 - 2 11 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 500 1 LED 3 LEDs 5 LEDs 7 LEDs SWITCHING FREQUENCY (kHz) 450 400 11 LEDs 13 LEDs 15 LEDs 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 50 60 SUPPLY VOLTAGE (V) Switching Frequency, L = 150H 100 90 80 DUTY CYCLE (%) 70 60 50 40 30 1 LED 3 LEDs 5 LEDs 7 LEDs 20 10 11 LEDs 13 LEDs 15 LEDs 0 0 10 20 30 40 SUPPLY VOLTAGE (V) Duty Cycle, L = 150H ZXLD1366 Document number: DS31992 Rev. 7 - 2 12 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 1.100 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs OUTPUT CURRENT (A) 1.080 1.060 1.040 1.020 1.000 0.980 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) Output Current, L = 220H 10 OUTPUT CURRENT DEVIATION (%) 8 6 4 2 0 -2 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs -4 -6 -8 -10 0 10 20 30 40 50 60 50 60 SUPPLY VOLTAGE (V) Output Current Deviation, L = 220H EFFICIENCY (%) 1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 LEDs 13 LEDs 15 LEDs 0 10 20 30 40 SUPPLY VOLTAGE (V) Efficiency, L = 220H ZXLD1366 Document number: DS31992 Rev. 7 - 2 13 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 500 1 LED 3 LEDs 5 LEDs 7 LEDs SWITCHING FREQUENCY (kHz) 450 400 11 LEDs 13 LEDs 15 LEDs 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 50 60 SUPPLY VOLTAGE (V) Switching Frequency, L = 220H 100 90 80 DUTY CYCLE (%) 70 60 50 40 1 LED 3 LEDs 5 LEDs 7 LEDs 30 20 11 LEDs 13 LEDs 15 LEDs 10 0 0 10 20 30 40 SUPPLY VOLTAGE (V) Duty Cycle, L = 220H ZXLD1366 Document number: DS31992 Rev. 7 - 2 14 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 1200 800 R = 300m 700 1000 SUPPLY CURRENT (mA) LED CURRENT (mA) R = 200m 800 R = 680m 600 400 600 500 400 300 200 200 100 0 0 1 2 ADJ PIN VOLTAGE (V) LED Current vs. ADJ 10 20 30 40 50 60 70 60 70 SUPPLY VOLTAGE (V) 1.2430 90 1.2425 80 SHUTDOWN CURRENT (mA) 1.2420 ADJ PIN VOLTAGE (V) 0 0 3 1.2415 1.2410 1.2405 1.2400 1.2395 1.2390 70 60 50 40 30 20 10 1.2385 1.2380 0 10 20 30 40 50 60 70 Document number: DS31992 Rev. 7 - 2 0 10 20 30 40 50 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) ZXLD1366 0 15 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Typical Operating Conditions (cont.) 1.6 -40C 20C 150C 1.4 ON-RESISTANCE () 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5 10 15 20 25 SUPPLY VOLTAGE (V) LX On-Resistance vs. Supply Voltage 30 35 1.262 1.260 1.258 7V 9V 12V 20V 30V VADJ (V) 1.256 1.254 1.252 1.250 1.248 1.246 1.244 -50 0 50 100 TEMPERATURE (C) VADJ vs. Temperature 150 200 1.6 ON-RESISTANCE () 1.4 1.2 7V 9V 12V 20V 30V 1.0 0.8 0.6 0.4 0.2 0 -50 ZXLD1366 Document number: DS31992 Rev. 7 - 2 0 50 100 150 DIE TEMPERATURE (C) LX On-Resisitance vs. Die Temperature 16 of 30 www.diodes.com 200 May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information Setting Nominal Average Output Current with External Resistor RS The nominal average output current in the LED(s) is determined by the value of the external current sense resistor (RS) connected between VIN and ISENSE and is given by: IOUTnom = 0.2/RS for RS 0.2 The table below gives values of nominal average output current for several preferred values of current setting resistor (RS) in the typical application circuit shown on page 1: RS () Nominal Average Output Current (mA) 0.20 1000 0.27 740 0.56 357 The above values assume that the ADJ pin is floating and at a nominal voltage of VREF (= 1.25V). Note that RS = 0.2 is the minimum allowed value of sense resistor under these conditions to maintain switch current below the specified maximum value. It is possible to use different values of RS if the ADJ pin is driven from an external voltage. (See next section). Output Current Adjustment by External DC Control Voltage The ADJ pin can be driven by an external dc voltage (VADJ), as shown, to adjust the output current to a value above or below the nominal average value defined by RS. ZXLD1366 ADJ + GND DC GND The nominal average output current in this case is given by: IOUTdc = (VADJ /1.25) x (0.2/RS) for 0.3< VADJ <2.5V Note that 100% brightness setting corresponds to proportion to prevent IOUTdc exceeding 1A maximum. VADJ = VREF. When driving the ADJ pin above 1.25V, RS must be increased in The input impedance of the ADJ pin is 50k 25% for voltages below VREF and 14.2k 25% for voltages above VREF +100mV. Output Current Adjustment by PWM Control Directly Driving ADJ Input A Pulse Width Modulated (PWM) signal with duty cycle DPWM can be applied to the ADJ pin, as shown below, to adjust the output current to a value above or below the nominal average value set by resistor RS: PWM VADJ ADJ 0V ZXLD1366 GND GND ZXLD1366 Document number: DS31992 Rev. 7 - 2 17 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Driving the ADJ Input via Open Collector Transistor The recommended method of driving the ADJ pin and controlling the amplitude of the PWM waveform is to use a small NPN switching transistor as shown below: ADJ PWM ZXLD1366 GND GND This scheme uses the 50k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the external transistor. Driving the ADJ Input from a Microcontroller Another possibility is to drive the device from the open drain output of a microcontroller. The diagram below shows one method of doing this: MCU 3.3k ADJ ZXLD1366 GND If the NMOS transistor within the microcontroller has high Gate / Drain capacitance, this arrangement can inject a negative spike into ADJ input of the ZXLD1366 and cause erratic operation but the addition of a Schottky clamp diode (eg Diodes Inc. SD103CWS) to ground and inclusion of a series resistor (3.3k) will prevent this. See the section on PWM dimming for more details of the various modes of control using high frequency and low frequency PWM signals. Shutdown Mode Taking the ADJ pin to a voltage below 0.2V for more than approximately 100s will turn off the output and supply current to a low standby level of 65A nominal. Note that the ADJ pin is not a logic input. Taking the ADJ pin to a voltage above VREF will increase output current above the 100% nominal average value. (See page 18 graphs for details). ZXLD1366 Document number: DS31992 Rev. 7 - 2 18 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Soft-Start An external capacitor from the ADJ pin to ground will provide a soft-start delay, by increasing the time taken for the voltage on this pin to rise to the turn-on threshold and by slowing down the rate of rise of the control voltage at the input of the comparator. Adding capacitance increases this delay by approximately 0.2ms/nF. The graph below shows the variation of soft-start time for different values of capacitor. 16 14 SOFT-START TIME (ms) 12 10 8 6 4 2 0 -2 0 20 40 60 80 100 120 CAPACITANCE (nF) Soft-Start Time vs. Capacitance form ADJ to Ground Actual Operating Waveforms [VIN = 60V, RS = 0.2, L = 68H, 22nF on ADJ] Soft-start operation. LX voltage (CH2) and Output current (CH3) using a 22nF external capacitor on the ADJ pin. ZXLD1366 Document number: DS31992 Rev. 7 - 2 19 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) VIN Capacitor Selection A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in series with the supply source impedance and lowers overall efficiency. This capacitor has to supply the relatively high peak current to the coil and smooth the current ripple on the input supply. To avoid transients into the IC, the size of the input capacitor will depend on the VIN voltage: VIN = 6 to 40V CIN = 2.2F VIN = 40 to 50V CIN = 4.7F VIN = 50 to 60V CIN = 10F When the input voltage is close to the output voltage the input current increases which puts more demand on the input capacitor. The minimum value of 2.2F may need to be increased to 4.7F; higher values will improve performance at lower input voltages, especially when the source impedance is high. The input capacitor should be placed as close as possible to the IC. For maximum stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric is recommended. Capacitors with Y5V dielectric are not suitable for decoupling in this application and should NOT be used. When higher voltages are used with the CIN = 10F, an electrolytic capacitor can be used provided that a suitable 1F ceramic capacitor is also used and positioned as close to the VIN pin as possible. A suitable capacitor would be NACEW100M1006.3x8TR13F (NIC Components). The following web sites are useful when finding alternatives: www.murata.com www.niccomp.com www.kemet.com Inductor Selection Recommended inductor values for the ZXLD1366 are in the range 68H to 220H. Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range. (see graphs pages 10-17). The inductor should be mounted as close to the device as possible with low resistance connections to the LX and VIN pins. 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 ZXLD1366 may be selected from the MSS range manufactured by Coilcraft, or the NPIS range manufactured by NIC components. The following websites may be useful in finding suitable components. www.coilcraft.com www.niccomp.com www.wuerth-elektronik.de The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the specified limits over the supply voltage and load current range. The graph Figure 3 below can be used to select a recommended inductor based on maintaining the ZXLD1366 case temperature below +60C. For detailed performance characteristics for the inductor values 68, 100, 150 and 220H see graphs on pages 10-17. ZXLD1366 Document number: DS31992 Rev. 7 - 2 20 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Minimum Recommended Inductor 2% Accuracy, <60C Case Temperature 15 Legend 14 68uH 13 100uH 12 150uH Number of LEDs 11 220uH 10 9 8 7 6 5 4 3 2 1 0 10 20 30 40 50 60 Supply Voltage (V) Figure. 3 ZXLD1366 Minimum Recommended Inductor (TSOT25) M in im u m R e c o m m e n d e d In d u c to r 2% Accuracy, <60C C ase T em perature 16 15 14 Legend 68H 100H 13 150H 12 220H N um ber of LED s 11 10 9 8 7 6 5 4 3 2 1 0.00 10.00 20.00 30.00 40.00 50.00 60.00 Supply Voltage (V) Figure. 4 ZXLD1366 Minimum Recommended Inductor (U-DFN3030-6) ZXLD1366 Document number: DS31992 Rev. 7 - 2 21 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) TC < 70C, I LED = 1A 15 14 Legend 13 47H Number of LEDs 12 68H 11 100H 10 150H 9 8 7 6 150H 5 100H 4 68H 3 47H 2 1 0 10 20 30 40 50 60 Supply Voltage (V) Figure. 5 ZXLD1366 Minimum Recommended Inductor (SO-8EP) 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. They also provide better efficiency than silicon 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. It is very important to consider the reverse leakage of the diode when operating above 85C. Excess leakage will increase the power dissipation in the device and if close to the load may create a thermal runaway condition. The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the LX output. If a silicon diode is used, care should be taken to ensure that the total voltage appearing on the LX pin including supply ripple, does not exceed the specified maximum value. *A suitable Schottky diode would be B3100 (Diodes Inc). ZXLD1366 Document number: DS31992 Rev. 7 - 2 22 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Reducing Output Ripple Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor Cled across the LED(s) as shown below: D1 VIN Rs LED Cled L1 VIN ISENSE LX ZXLD1366 Figure. 6 Reduced Output Ripple A value of 1F 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 sinusoidal version without altering the mean current value. Operation at Low Supply Voltage Below the under-voltage lockout threshold (VSD) the drive to the output transistor is turned off to prevent device operation with excessive onresistance of the output transistor. The output transistor is not full enhanced until the supply voltage exceeds approximately 17V. At supply voltages between VSD and 17V care must be taken to avoid excessive power dissipation due to the on-resistance. Note that when driving loads of two or more LEDs, the forward drop will normally be sufficient to prevent the device from switching below approximately 6V. This will minimize the risk of damage to the device. ZXLD1366 Document number: DS31992 Rev. 7 - 2 23 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Thermal Considerations When operating the device at high ambient temperatures, or when driving maximum load current, care must be taken to avoid exceeding the 2 package power dissipation limits. The graph below gives details for power derating. This assumes the device to be mounted on a 25mm PCB with 1oz copper standing in still air. 2.5 POWER DISSIPATION (W) SO-8EP 2.0 U-DFN3030-6 1.5 1.0 TSOT25 0.5 0 -40 -25 -10 5 20 35 50 65 80 -5 110 125 AMBIENT TEMPERATURE (C) Maximum Power Dissipation Note that the device power dissipation will most often be a maximum at minimum supply voltage. It will also increase if the efficiency of the circuit is low. This may result from the use of unsuitable coils, or excessive parasitic output capacitance on the switch output. In order to maximize the thermal capabilities of the DFN3030-6 and the SO-8EP packages thermal vias should be incorporated into the PCB. See figures 7 and 8 for examples used in the ZXLD1366 evaluation boards. Figure. 7 Suggested Layout for U-DFN3030-6 Package ZXLD1366 Document number: DS31992 Rev. 7 - 2 24 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) Figure. 8 Suggested Layout for SO-8EP Package Vias ensure an effective path to the ground plane for the heat flow therefore reducing the thermal impedance between junction and ambient temperature. Diodes came to the conclusion that the compromise is reached by using more than 10 vias with 1mm of diameter and 0.5 hole size. Finally the same scheme in Figure 7 (without the exposed paddle) can be usde for the TSOT25 package guaranteeing an effective thermal path. Thermal Compensation of Output Current High luminance LEDs often need to be supplied with a temperature compensated current in order to maintain stable and reliable operation at all drive levels. The LEDs are usually mounted remotely from the device so, for this reason, the temperature coefficients of the internal circuits for the ZXLD1366 have been optimized to minimize the change in output current when no compensation is employed. If output current compensation is required, it is possible to use an external temperature sensing network normally using Negative Temperature Coefficient (NTC) thermistors and/or diodes, mounted very close to the LED(s). The output of the sensing network can be used to drive the ADJ pin in order to reduce output current with increasing temperature. Layout Considerations LX Pin The LX pin of the device is a fast switching node, so PCB tracks should be kept as short as possible. To minimize ground 'bounce', the ground pin of the device should be soldered directly to the ground plane. Coil and Decoupling Capacitors and Current Sense Resistor It is particularly important to mount the coil and the input decoupling capacitor as close to the device pins as possible to minimize parasitic resistance and inductance, which will degrade efficiency. It is also important to minimize any track resistance in series with current sense resistor RS. Its best to connect VIN directly to one end of RS and ISENSE directly to the opposite end of RS with no other currents flowing in these tracks. It is important that the cathode current of the Schottky diode does not flow in a track between RS and VIN as this may give an apparent higher measure of current than is actual because of track resistance. ADJ Pin The ADJ pin is a high impedance input for voltages up to 1.35V so, when left floating, PCB tracks to this pin should be as short as possible to reduce noise pickup. A 100nF capacitor from the ADJ pin to ground will reduce frequency modulation of the output under these conditions. An additional series 3.3k resistor can also be used when driving the ADJ pin from an external circuit (see next page). This resistor will provide filtering for low frequency noise and provide protection against high voltage transients. ZXLD1366 Document number: DS31992 Rev. 7 - 2 25 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Application Information (cont.) 3.3k ZXLD1366 ADJ GND 100nF GND High Voltage Tracks Avoid running any high voltage tracks close to the ADJ pin, to reduce the risk of leakage currents due to board contamination. The ADJ pin is soft-clamped for voltages above 1.35V to desensitize it to leakage that might raise the ADJ pin voltage and cause excessive output current. However, a ground ring placed around the ADJ pin is recommended to minimize changes in output current under these conditions. Evaluation PCB ZXLD1366 evaluation boards are available on request. Terminals allow users to interface the boards to their preferred LED products. Dimming Output Current Using PWM Low Frequency PWM Mode When the ADJ pin is driven with a low frequency PWM signal (eg 100Hz), with a high level voltage VADJ and a low level of zero, the output of the internal low pass filter will swing between 0V and VADJ, causing the input to the shutdown circuit to fall below its turn-off threshold (200mV nom) when the ADJ pin is low. This will cause the output current to be switched on and off at the PWM frequency, resulting in an average output current IOUTavg proportional to the PWM duty cycle. (See Figure 9 - Low frequency PWM operating waveforms). The average value of output current in this mode is given by: IOUTavg 0.2DPWM/RS [for DPWM >0.001] This mode is preferable if optimum LED 'whiteness' is required. It will also provide the widest possible dimming range (approx. 1000:1) and higher efficiency at the expense of greater output ripple. VADJ Ton PWM Voltage Toff 0V IOUTnom 0.2/Rs Output Current IOUTavg 0 Figure. 9 Low Frequency PWM Operating Waveforms ZXLD1366 Document number: DS31992 Rev. 7 - 2 26 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Ordering Information ZXLD1366 XXX XX Part Number Package DAC : U-DFN3030-6 TC : 13" Tape & Reel TC : 13" Tape & Reel EN8 : SO-8EP TA : 7" Tape & Reel ET5 : TSOT25 ZXLD1366 Part Mark Device ZXLD1366DACTC ZXLD1366EN8TC ZXLD1366ET5TA Packing Packaging Reel Size (inches) Reel Width (mm) Quantity Per Reel Part Number Suffix 1366 ZXLD 1366 YYWW U-DFN3030-6 13 12 3000 TC SO-8EP 13 12 2500 TC Grade 1 1366 TSOT25 7 8 3000 TA Grade 1 AEC-Q100 Where YY stands for last 2 digits of year - 10, 11 and WW stands for week number. Package Outline Dimensions 1) TSOT25 D e1 E E1 L2 c 4x 1 e L 5x b A A2 A1 ZXLD1366 Document number: DS31992 Rev. 7 - 2 27 of 30 www.diodes.com TSOT25 Dim Min Max Typ A 1.00 - - A1 0.01 0.10 - A2 0.84 0.90 - D 2.90 - - E 2.80 - - E1 1.60 - - b 0.30 0.45 - c 0.12 0.20 - e 0.95 - - e1 1.90 - - L 0.30 0.50 L2 0.25 - - 0 8 4 1 4 12 - All Dimensions in mm May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Package Outline Dimensions (cont.) 2) U-DFN3030-6 A U-DFN3030-6 Dim Min Max Typ A 0.57 0.63 0.60 A1 0 0.05 0.02 A3 0.15 b 0.29 0.39 0.34 D 2.9 3.1 3.0 D2 2.65 2.85 2.75 E 2.9 3.1 3.0 e 1.205 E2 1.76 1.96 1.86 L 0.30 0.60 0.45 All Dimensions in mm A3 A1 D e E E2 L b D2 3) SO-8EP Exposed Pad 8 5 E1 1 H 4 F b Bottom View E 9 (All sides) N 7 A e D A1 ZXLD1366 Document number: DS31992 Rev. 7 - 2 45 Q C 4 3 Gauge Plane Seating Plane E0 L 28 of 30 www.diodes.com SO-8EP (SOP-8L-EP) Dim Min Max Typ A 1.40 1.50 1.45 A1 0.00 0.13 b 0.30 0.50 0.40 C 0.15 0.25 0.20 D 4.85 4.95 4.90 E 3.80 3.90 3.85 E0 3.85 3.95 3.90 E1 5.90 6.10 6.00 e 1.27 F 2.75 3.35 3.05 H 2.11 2.71 2.41 L 0.62 0.82 0.72 N 0.35 Q 0.60 0.70 0.65 All Dimensions in mm May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 Suggested Pad Layout 1) TSOT25 C C Dimensions Value (in mm) C 0.950 X 0.700 Y 1.000 Y1 3.199 Y1 Y (5x) X (5x) 2) U-DFN3030-6 Y C Dimensions Value (in mm) Z 2.75 G 0.57 X1 1.86 X2 0.45 Y 0.34 C 1.205 X2 G X1 Z 3) SO-8EP X Exposed Pad X1 Dimensions X Y X1 Y1 C1 C2 C1 Y1 Y Value (in mm) 0.60 1.55 3.30 2.66 5.4 1.27 C2 ZXLD1366 Document number: DS31992 Rev. 7 - 2 29 of 30 www.diodes.com May 2012 (c) Diodes Incorporated A Product Line of Diodes Incorporated ZXLD1366 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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