ZXLD1356

ZXLD1356/ ZXLD1356Q

Document overview

Manufacturer or author: Diodes Incorporated
PDF pages: 29

Technical content

Features

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%)
Wide input voltage range: 6V to 60V
Inherent open-circuit LED protection
Available in thermally enhanced packages V-DFN3030-6 θJA 44°C/W TSOT25 θJA 82°C/W
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)
ZXLD1356QET5TA Automotive Grade qualified to AEC-Q100 Grade 1 Pin Assignments (TOP VIEW) TSOT25 ISENSE VIN 3 4 ADJ GND LX V-DFN3030-6 (TOP VIEW) LX GND ADJ VIN ISENSE GND

Applications

Low Voltage Halogen Replacement LEDs
Automotive Lighting
Low Voltage Industrial Lighting
LED Back-Up Lighting
Illuminated Signs
Emergency Lighting
SELV Lighting
Refrigeration Lights Notes: 1. No purposely added lead. Fully EU Directiv e 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. 2. See http://www.diodes.com for more in formation 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.

Document number: DS33470 Rev. 4 - 2 2 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Applications Circuit VIN ISENSE LX GND ZXLD1356ADJ VIN (24V) Rs 0.36V 4.7µFC1 GND 100nF Pin Descriptions Pin Name Pin Number Function TSOT25 V-DFN3030-6 LX 1 1 Drain of NDMOS switch GND 2 2, 5 Ground (0V) ADJ 3 3 Multi-function On/Off and brightness control pin:

Leave floating for normal operation.(V ADJ = VREF = 1.25V giving nominal average output current o I OUTnom = 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 24% to 200% of IOUTnom
Connect a capacitor from this pin to ground to define soft-start time. Soft-start time is approx.0.2ms/nF ISENSE 4 4 Connect resistor RS from this to VIN to define nominal average output current IOUTnom = 0.2/RS (Note: RSMIN=0.36V with ADJ pin open circuit) VIN 5 6 Input voltage (6V to 60V). Decouple to ground with 4.7µF of higher X7R ceramic capacitor close to device Pad — Pad Exposed pad (EP) - connected to device substrate. To improve thermal impedance of package the EP must be connected to power 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.

Figure 1. Block Diagram – Pin Connections Shown for TSOT25 Package These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Operation at the absolute maximum rating for extended periods may reduce device reliability. The human body model is a 100pF capacitor discharge through a 1.5kΩ resistor pin. The machine model is a 200pF capacitor discharged directly into each pin.

Document number: DS33470 Rev. 4 - 2 4 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Thermal Resistance Symbol Parameter Rating Unit TSOT25 V-DFN3030-6 θJA Junction to Ambient 82 44 °C/W ΨJB Junction to Board 33 — °C/W θJC Junction to Case — 14 °C/W Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Symbol Parameter Min Max Units VIN Input voltage (Note 4) 6 60 V tOFFMIN Minimum switch off-time 800 ns tONMIN Minimum switch on-time 800 ns fLX max Recommended maximum operating frequency (Note 5) 625 kHz DLX Duty cycle range 0.01 0.99 TOP Operating temperature range -40 +125 °C Notes: 4. V IN > 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. 5. ZXLD1356 will operate at higher frequencies but accuracy will be affected due to propagation delays.

Document number: DS33470 Rev. 4 - 2 5 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Electrical Characteristics (VIN = 24V, @TAMB = +25°C, unless otherwise specified.) Symbol Parameter Condition Min Typ Max Unit VSU Internal regulator start-up threshold 4.85 5.2 V VSD Internal regulator shutdown threshold 4.40 4.75 V IINQoff Quiescent supply current with output off ADJ pin grounded 65 108 µA IINQon Quiescent supply current with output switching (Note 6) ADJ pin floating, L = 68mH, 3 LEDsf = 360kHz 1.6 mA VSENSE Mean current sense threshold voltage (Defines LED current setting accuracy) Measured on ISENSE pin with respect to VIN VADJ = 1.25V; VIN = 18V 195 200 205 mV VSENSEHYS Sense threshold hysteresis ±15 % ISENSE I SENSE pin input current VSENSE = VIN -0.2 4 10 µA VREF Internal reference voltage Measured on ADJ pin with pin floating 1.25 V ΔVREF/ΔT Temperature coefficient of V REF 50 ppm/°C VADJ External control voltage range on ADJ pin for DC brightness control (Note 7) 0.3 2.5 V VADJoff DC voltage on ADJ pin to switch device from active (on) state to quiescent (off) state VADJ falling 0.15 0.20 0.27 V VADJon DC voltage on ADJ pin to switch device from quiescent (off) state to active (on) state VADJ rising 0.2 0.25 0.3 V RADJ Resistance between ADJ pin and V REF 0< V ADJ < VREF, VADJ > VREF +100mV 30 10.4 14.2 18.0 kΩ ILXmean Continuous LX switch current 0.55 A RLX LX switch ‘On’ resistance @ ILX = 0.55A 0.5 0.75 Ω ILX(leak) LX switch leakage current 5 µA DPWM(LF) Duty cycle range of PWM signal applied to ADJ pin during low frequency PWM dimming mode PWM frequency <300Hz PWM amplitude = V REF Measured on ADJ pin 0.001 1 Brightness control range 1000:1 DCADJ (*) DC Brightness control range Note 8 5:1 tSS Start up time (See graphs for more details) 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. 2 ms fLX Operating frequency (See graphs for more details) ADJ pin floating L= 68mH (0.36V) IOUT = 0.55A @ VLED = 3.6V Driving 3 LEDs 360 kHz fLXmax Recommended maximum operating frequency 500 kHz Notes: 6. Static current of device is approximately 700 µA, see Graph, Page 17. 7. 100% brightness corresponds to V ADJ = VADJ(nom) = VREF. Driving the ADJ pin above VREF will increase the VSENSE. threshold and output current proportionally.

The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a self-oscillating continuous-mode buck converter. Figure 2. Theoretical Operating Waveforms at the (+) input of the comparator. internal resistor R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of VADJ. switches high again. This cycle of events repeats, with the comparator input ramping between limits of VADJ ± 15%.

Document number: DS33470 Rev. 4 - 2 7 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Device Description (cont.) Adjusting Output Current The device contains a low pass filter between the ADJ pin and the threshold comparator and an internal current limiting resisto r (50kΩ nom) between ADJ and the internal reference voltage. This allows the ADJ pin to be overdriven with ei ther DC or pulse signals to change the V SENSE switching threshold and adjust the output current. Details of the different modes of adjusting output current are given in the applications section. Output Shutdown 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 volt age reference remains powered during shutdown to provide the b ias current for the shutdown circuit. Quiescent supply current during shutdown is nominally 60µA and switch leakage is below 5µA.

Document number: DS33470 Rev. 4 - 2 8 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Actual Operating Waveforms [VIN = 15V, RS = 0.36V, L = 68µH] Normal operation. Output current (Ch3) and LX voltage (Ch2) Actual Operating Waveforms [VIN = 30V, RS = 0.36V, L = 68µH] Normal operation. Output current (Ch3) and LX voltage (Ch2) Actual Operating Waveforms [VIN = 60V, RS = 0.36V, L = 68µH] Normal operation. Output current (Ch3) and LX voltage (Ch2)

Document number: DS33470 Rev. 4 - 2 9 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions 0.500 Output Current (A) 0.520 0.540 0.560 0.580 0.600 0.620 0.640

15 LEDs13 LEDs11 LE Ds9 LEDs7 LEDs5 LEDs3 LEDs1 LED

Supply Voltage (V) ZXLD1356 Output Current L = 68µH ZXLD1356 Output Current Deviation (Normalized) L = 68µH Supply Voltage (V) 10% -10% -8% -6% -4% -2% Output Current Deviation (%) Supply Voltage (V) ZXLD1356 Efficienc y L = 68µH 100% 95% 50% 55% 60% 90% 65% 70% 75% 80% 85% Ef ficiency (%)

Document number: DS33470 Rev. 4 - 2 10 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) ZXLD1356 Switching Frequenc y L = 68µH Supply Voltage (V) 700 600 500 400 300 100 200 Switching Frequency (kHz) Supply Voltage (V) ZXLD1356 Duty Cycle L = 68µH 100 Duty Cycle (%)

Document number: DS33470 Rev. 4 - 2 11 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) ZXLD1356 Output Current L = 100µH Supply Voltage (V) 0.500 Output Current (A) 0.520 0.540 0.560 0.580 0.600 0.620 0.640 ZXLD1356 Output Current Deviation (Normalized) L = 100µH 10% -10% -8% -6% -4% -2% Output Current Deviation (%) Supply Voltage (V) Supply Voltage (V) ZXLD1356 Efficienc y L = 100µH 100% 95% 50% 55% 60% 90% 65% 70% 75% 80% 85% Ef ficiency (%)

Document number: DS33470 Rev. 4 - 2 12 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) ZXLD1356 Switching Frequenc y L = 100µH Supply Voltage (V) 700 600 500 400 300 100 200 Switching Frequency (kHz) Supply Voltage (V) ZXLD1356 Duty Cycle L = 100µH 100 Duty Cycle (%)

Document number: DS33470 Rev. 4 - 2 13 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) ZXLD1356 Output Current L = 150µH Supply Voltage (V) 0.500 Output Current (A) 0.520 0.540 0.560 0.580 0.600 0.620 0.640 Supply Voltage (V) 10% -10% -8% -6% -4% -2% Output Current Deviation (%) ZXLD1356 Output Current Deviation (Normalized) L = 150µH Supply Voltage (V) ZXLD1356 Efficienc y L = 150µH 100% 95% 50% 55% 60% 90% 65% 70% 75% 80% 85% Ef ficiency (%)

Document number: DS33470 Rev. 4 - 2 14 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) Supply Voltage (V) ZXLD1356 Switching Frequenc y L = 150µH 700 600 500 400 300 100 200 Switching Frequency (kHz) Supply Voltage (V) 100 Duty Cycle (%) ZXLD1356 Duty Cycle L = 150µH

Document number: DS33470 Rev. 4 - 2 15 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) ZXLD1356 Output Current L = 220µH Supply Voltage (V) 0.500 Output Current (A) 0.520 0.540 0.560 0.580 0.600 0.620 0.640 ZXLD1356 Output Current Deviation (Normalized) L = 220µH Supply Voltage (V) 10% -10% -8% -6% -4% -2% Output Current Deviation (%) ZXLD1356 Efficienc y L = 220µH Supply Voltage (V) 100% 95% 50% 55% 60% 90% 65% 70% 75% 80% 85% Ef ficiency (%)

Document number: DS33470 Rev. 4 - 2 16 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) Supply Voltage (V) ZXLD1356 Switching Frequency L = 220µH 700 600 500 400 300 100 200 Switching Frequency (kHz) ZXLD1356 Duty Cycle L = 220µH Supply Voltage (V) 100 Duty Cycle (%)

Document number: DS33470 Rev. 4 - 2 17 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) LED Current vs Vadj 100 200 300 400 500 600 0123 ADJ Pin Voltage (V) LED Current (mA) R=0.36Ω R=0.56Ω R=1.33Ω Vref 1.238 1.2385 1.239 1.2395 1.24 1.2405 1.241 1.2415 1.242 1.2425 1.243 0 1 02 03 0 4 05 06 07 0 ADJ pin voltage (V) Supply current 100 200 300 400 500 600 700 800 0 1 02 03 04 05 06 07 0 Supply voltage (V) Supply voltage (V) Supply voltage (V) Supply current (mA) Shutdown current 0 1 02 03 0 4 05 06 07 0 Shutdown current (mA) Output transistor fully enhanced Output transistor not fully enhanced

Document number: DS33470 Rev. 4 - 2 18 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Typical Operating Conditions (cont.) Lx on-resistance vs die temperature 0.2 0.4 0.6 0.8 1.2 1.4 1.6 -50 0 50 100 150 200 Die Temperature (C) On-resistance (Oh ms) 12V 20V 30V Vadj vs Temperature 1.244 1.246 1.248 1.25 1.252 1.254 1.256 1.258 1.26 1.262 -50 0 50 100 150 200 Temperature (C) Vadj (V) 12V 20V 30V 0.5 1.5 2.5 0 1 02 03 04 05 06 07 0 Supply Voltage (V) On-resistance (Ohms) -40 oC 25 oC 125 oC Lx on-resistance vs supply voltage

Document number: DS33470 Rev. 4 - 2 19 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated

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 (R S) connected between V IN and ISENSE and is given by: IOUTnom = 0.2/RS [for RS > 0.36Ω] The table below gives values of nominal average output current for several preferred values of current setting resistor (R S) in the typical application circuit shown on page 1: RS(Ω) Nominal Average Output Current (mA) 0.36 555 0.56 357 1.33 150 The above values assume that the ADJ pin is floating and at a nominal voltage of V REF (= 1.25V). Note that R S = 0.36V 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 (V ADJ), as shown, to adjust the output current to a value above or below the nominal average value defined by RS. GND ZXLD1356ADJ GND DC 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 V ADJ = V REF. When driving the ADJ pin above 1.25V, R S must be increased in proportion to prevent IOUTdc exceeding 550mA maximum. The input impedance of the ADJ pin is 50kΩ ±25% for voltages below VREF and 14.2kΩ ±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 D PWM 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 GND VADJ GND ZXLD1356ADJ

Document number: DS33470 Rev. 4 - 2 20 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Application Information (cont.) Driving the ADJ Input via Open Collector Transistor The recommended method of driving the ADJ pin and controlling the am plitude of the PWM waveform is to use a small NPN switching transistor as shown below: PWM GND ZXLD1356ADJ 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 eg MMBT3904. 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: GND ZXLD1356ADJ MCU 3.3k If the NMOS transistor within the microcontroller has high Gate / Drain capacitance, this arrangement can inject a negative spi ke into ADJ input of the ZXLD1356 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 PW M dimming for more details of t he various modes of control usi ng high frequency and low frequency PWM signals. Shutdown Mode Taking the ADJ pin to a voltage below 0.2V for more than approximately 100µs will turn off the output and supply current to a l ow standby level of 65µA nominal. Note that the ADJ pin is not a logic input. Taking the ADJ pin to a voltage above V REF will increase output current above the 100% nominal average value. (See page 17 graphs for details). 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 capaci tance increases this delay by approximately 0.2ms/nF. The graph on the next page shows the variation of soft-start time for different values of capacitor.

Document number: DS33470 Rev. 4 - 2 21 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Application Information (cont.) Soft-Start (cont.) Soft Start Time vs Capacitance from ADJ pin to Ground 0 2 04 06 08 0 1 00 1 20 Capacitance (nf) Soft Start Time (ms) Actual Operating Waveforms [VIN = 60V, RS = 0.36V, L = 68µH, 22nF on ADJ] Soft-start operation. LX voltage (Ch2) and Output current (Ch3) using a 22nF external capacitor on the ADJ pin.

Document number: DS33470 Rev. 4 - 2 22 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Application Information (cont.) VIN Capacitor Selection A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appea rs 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 rip ple 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 C IN = 2.2µF VIN = 40 to 50V C IN = 4.7µF VIN = 50 to 60V C IN = 10µF 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 2.2µF may need to be increased to 4.7µF; higher values will improve performance at lower input voltages, especially wh en 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 w ith Y5V dielectric are not suitable for decoupling in this application and should NOT be used. When higher voltages are with CIN = 10µF, an electrolytic capacitor can be used provided that a suitable 1m F 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 ZXLD1356 are in the range 68 µH to 220 µH. Higher values of inductance are recommended at higher supply voltages in order to minimi ze errors due to switching delays, whic h result in increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the s upply voltage range. (see graphs pages 10-16). The inductor should be mounted as close to the device as po ssible 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 ZXLD1356 may be selected from th e MSS range manufactured by Coilcraft, or the NPIS range manufa ctured 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. Figures 3 and 4 (following) can be used to select a recommended inductor based on maintaining the ZXLD1356 case temperature bel ow 60°C for the different package types. For detail ed performance characteristics for the in ductor values 68, 100, 150 and 220µH see gr aphs on pages 10-16.

Figure 3. ZXLD1356 Minimum Recommended Inductor 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. the power dissipation in the device and if close to the load may create a thermal runaway condition. *A suitable Schottky diode would be B1100B (Diodes Inc).

Document number: DS33470 Rev. 4 - 2 24 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated 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: VIN VIN ISENSE LX ZXLD1356 Rs CledLED A value of 1µF will reduce the supply ripple current by a fact or three (approx.). Proportionally lower ripple can be achieved w ith higher capacitor values. Note that the capacitor will not affect operating frequenc y or efficiency, but it will increase start-up delay, by redu cing 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 wi thout altering the mean current value. Operation at Low Supply Voltage Below the under-voltage lockout threshold (V SD) the drive to the output transistor is turned o ff to prevent device operation with excessive on- resistance 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 switc hing below approximately 6V. This will minimize the risk of damage to the device. Thermal Considerations When operating the device at high ambient temp eratures, or when driving maximum load cu rrent, care must be taken to avoid excee ding the package power dissipation limits. The graph below gives details fo r power derating. This assumes the device to be mounted on a (25mm) PCB with 1oz copper standing in still air. TSOT23-5 DFN3030-6 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 -40 -25 -10 5 20 35 50 65 80 95 110 125 Ambient Temperature (°C) 140 Maximum Power Dissipation Power Dissipation (W)

Document number: DS33470 Rev. 4 - 2 25 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Application Information (cont.) Thermal Considerations (cont.) Note that the device power dissipation will most often be a maxi mum at minimum supply voltage. It will also increase if the eff iciency of the circuit is low. This may result from the use of unsuitable coils, or excessive parasitic output capacitance on the switch output. 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 o peration at all drive levels. The LEDs are usually mounted remotely from the devic e so, for this reason, the temperature coefficients of the i nternal circuits for the ZXLD1356 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 tr acks should be kept as short as possible. To minimize ground 'bounc e', 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 decoup ling capacitor as close to the device pins as possible to mi nimize parasitic resistance and inductance, which will degrade effi ciency. 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 R S 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 R S and V IN 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 shor t as possible to reduce noise pickup. A 100nF capacitor from the ADJ pin to gr ound will reduce frequency modulation of the output under these co nditions. An additional series 3.3kΩ resistor can also be used when driving the ADJ pin from an exte rnal circuit (see below). This resistor will provide filtering for low frequency noise and provide protection against high voltage transients. GND ZXLD1356ADJ 3.3k 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 desens itize it to leakage that might raise the ADJ pin voltage and cause excessive out put current. However, a ground ring placed around the ADJ pin is recommended to minimize changes in output current under these conditions. Evaluation Boards ZXLD1356 evaluation boards are available on request, which have connection terminals that allow customers to connect their own LED products to the board.

average output current IOUTavg proportional to the PWM duty cycle. (See Figure 4 - Low frequency PWM operating waveforms). Figure 4. Low Frequency PWM Operating Waveforms higher efficiency at the expense of greater output ripple.

Document number: DS33470 Rev. 4 - 2 27 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated

Ordering Information

(inches) Reel Width (mm) Quantity per Reel Part Number Suffix Automotive Grade ZXLD1356DACTC 1356 DAC V-DFN3030-6 13 12 3000 TC ZXLD1356ET5TA 1356 ET5 TSOT25 7 8 3000 TA ZXLD1356QET5TA 1356 ET5 TSOT25 7 8 3000 TA Y (Note 9) Note: 9. For Automotive grade with AEC-Q100 Grade 1 qualification the ZXLD1356QET5TA should be ordered. Package Outline Dimensions (All dimensions in mm.) Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version. V-DFN3030-6 TSOT25 V-DFN3030-6 Dim Min Max Typ A 0.80 0.90 0.85 A1 0 0.05 - A3 - - 0.203 b 0.30 0.40 0.35 D 2.95 3.05 3.00 D2 1.95 2.05 2.00 E 2.95 3.05 3.00 E2 1.15 1.25 1.20 e - - 0.95 e1 - - 1.90 L 0.45 0.55 0.50 All Dimensions in mm 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 θ 0° 8° 4° θ1 4° 12° − All Dimensions in mm c L E1 E D e 5x b θ 4x 1 θ A L b e A Cha mfer 0. 300X45° Pi n #1 I D E D Seati ng Pl ane

Document number: DS33470 Rev. 4 - 2 28 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated Suggested Pad Layout Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. V-DFN3030-6 TSOT25 Dimensions Value (in mm) C 0.950 X 0.450 X1 2.100 Y 0.630 Y1 1.300 Y2 3.160 Dimensions Value (in mm) C 0.950 X 0.700 Y 1.000 Y1 3.199 Y1 C C X (5x) Y (5x) Y XC C - 0.329

Document number: DS33470 Rev. 4 - 2 29 of 29 www.diodes.com October 2012 © Diodes Incorporated ZXLD1356/ ZXLD1356Q A Product Line of Diodes Incorporated 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 ma ke modifications, enhancements, im provements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability ari sing out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporat ed and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability wh atsoever in respect of any products purchased through unauthoriz ed 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 representat ives harmless against all claims, damages, expenses, and attorney fees arising out 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 names 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 mu ltiple 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 comp onents 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 proper ly used in accordance with inst ructions for use provided in 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 devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning the ir products and any use of Diodes Incorporated products in such safety-critica l, 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 Incorporate d and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life suppor t devices or systems. Copyright © 2012, Diodes Incorporated www.diodes.com

Summary

High accuracy 550mA, 60V LED driver with internal switch

Description

The ZXLD1356 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input supply between 6V and 60V and provides an externally adjustable output current of up to 550mA. Depending upon supply voltage and external components, this can provide up to 30 watts of output power.

Source title ZXLD1356 Datasheet(PDF) - Diodes Incorporated

Read ZXLD1356 online.