ZXLD1370EV1 BUCK LED DRIVER USER GUIDE 0-1.5A DC DVM GND 8-48V 2A DC PSU 1 - 15 LEDs 1.5A 4.5V 0 – 4.5V Status steps 0V Open Drain output 2.5V = 200% 125mV = 10% -t° Thermal connection Fig. 1 ZXLD1370EV1 Evaluation board connection diagram Issue 2 – Sept 2010 © Diodes Incorporated, 2010 www.diodes.com LEDA LEDA GND THR LEDK LEDK 1 2 3 4 5 6 P8 P9 LEDK Issue 2 – Sept 2010 LEDA SK1 R2 P2 C4 2.2uF 100V GND GND C3 2.2uF 100V GND C2 1uF 100V R14 0R0 TP2 0.3R DDZX15 2 R6 0R 1.3k P7 TADJ C7 1 R3 0R ADJIN P6 R5 3 15 GND ADJ 0R C6 VAUX ISM REF Gate U1 ZXLD1370 10 Gate ADJ FLAG PW M STATUS GI LX R12 TP1 Q1 GMOS DMN6068LK3 TADJ 14 0R0 REF GND 5 R7 47k SHP SGND PGND 6 REF GND 13 VIN 4 R8 0R L1 33uH C8 1uF 100V 11 12 10k THERMR 1uF 100V D2 10K R11 R4 C5 VAUX R13 GND 16 2 Fig. 2 ZXLD1370EV1 Schematic Diagram C9 100nF 100V GND 0.3R R1 VIN 7 © Diodes Incorporated 2010 D1 SBR3U100LP FLAG FLAG P4 GND STATUS STATUS P5 C1 100pF PW M P3 GND GND P1 GND ZXLD1370EV1 www.diodes.com SHP ZXLD1370EV1 PARTS LIST Ref Value Package Part Number U1 LED Driver Controller 60V N-ch MOSFET Freewheeling diode 3A 100V NOT FITTED 33uH 2.3A TSSOP16 L- EP DPAK 100pF 10V 1uF 100V X7R 2.2uF 100V X7R NOT FITTED 100nF 100V X7R 0R3 0R 1206 0805 1K3 47K NOT FITTED 0R 0805 0805 1206 1206 Q1 D1 D2 L1 C1 C2 C5 C8 C3 C4 C6 C7 C9 R1 R2 R3 R5 R6 R8 R14 R4 R7 R11, R13 R12 Contact Details ZXLD1370 Manufacture r Diodes DMN6068LK3 Diodes www.diodes.com DFN3030 SBR3U100LP Diodes www.diodes.com SOT23 DDZX15 MS1246-333MLB NPIS24H330MTRF 744-7715330 Diodes Coilcraft NIC Comps. Wurth www.diodes.com www.coilcraft.com www.niccomp.com www.we-online.com 0805 1206 GRM31CR72A105KA01L Murata www.murata.com 1812 GRM43ER72A225KA01L Murata www.murata.com www.diodes.com 0805 NOTES The PCB is supplied with R3 and R8 0R0 resistors fitted. The ‘ADJ’ pin and the ‘TADJ’ pin are disabled. ‘VIN’ and ‘VAUX’ are shorted on ZXLD1370EV1 The LED current of the ZXLD1370EV1 boards = 1.5A with 2x // 0R3 = 0R15 (R1 & R2) The ZXLD1370 ‘VAUX’ pin can be driven from a separate supply instead of the ‘VIN’ voltage. To do this, remove R14, fit R11 = 10k0, fit R13 = 10k0. Use Zener diode D2 to keep ‘VAUX’ pin <15V. For other reference designs or more applications information, please see the ZXLD1370 datasheet. OPERATION In Buck mode, the LED current is sensed by the resistor (R1 // R2). An output from the control loop responsible for sensing this current drives the input of an internal comparator. The comparator drives the gate of the external NMOS switch transistor through the ‘GATE’ pin. When the NMOS switch is on, current flows from ‘VIN’, through (R1 // R2), the LED, the inductor and the switch to ground, and increases until a high value is reached. Then, ‘GATE’ goes low, the switch turns off and the current flows through (R1 // R2), the LED, the inductor and D1, back to ‘VIN’. When the inductor current has gone low, ‘GATE’ goes high, the switch turns on, and the cycle repeats resulting in the circuit oscillates. The average current in the LED equals the average of the maximum and minimum threshold currents. The ripple current (hysteresis) is equal to the difference between the thresholds. The control loop keeps the average LED current at the level set by the voltage on the ‘ADJ’ pin. Loop compensation is achieved by C1. Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 3 ZXLD1370EV1 Fig. 3 Waveforms Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 4 ZXLD1370EV1 ADJ Terminal (DC output current adjustment) On the ZXLD1370EV1, R3 connects the ‘ADJ’ pin to ‘VREF’ to give 100% LED current. The ‘ADJ’ pin can be driven with an external DC voltage >=125mV and <=2.5V to adjust the LED current to >=10% and <=200% of the nominal value. To do this, remove R3, fit R5 and apply an external DC voltage between ‘ADJIN’ and ‘GND’. The voltage ‘VADJ ‘ can be derived from a resistor-divider connected between ‘REF’ and ‘GND’. ‘ADJ’ has a high impedance within its normal operating voltage range. An internal 2.6V clamp protects the device against high input voltages and limits the maximum output current to about 4% above the maximum current set by ‘VADJ ‘ if the maximum input voltage is exceeded. PWM Terminal (PWM output current control/dimming) The LED current can be adjusted digitally, by applying a low frequency PWM logic signal to the ‘PWM’ pin to turn the controller on and off. This will produce an average output current proportional to the duty cycle of the control signal. During PWM operation, the device remains powered-up and only the output is switched by the control signal. The device can be shut down by taking the ‘PWM’ pin to to <0.4V for >15ms with a short to 0V or suitable open collector NPN, or open drain NMOS transistor. In shutdown, most of the circuitry inside the device is off and the quiescent current will be typically 90µA. TADJ Terminal (Thermal control of LED current) The Thermal control circuit monitors the voltage on the ‘TADJ’ pin and reduces the output current linearly if the voltage on ‘TADJ’ < 625mV. An NTC thermistor and resistor can be connected to set the voltage on the ‘TADJ’ pin = 625mV at the required threshold temperature. This will give 100% LED current below the threshold temperature and <100% current above it as shown in the graph. The temperature threshold can be changed by adjusting the value of Rth and/or the thermistor to suit the LED used. On the ZXLD1370EV1, Rth is 1K3 (R4). To use Thermal control, remove R8, fit R6, and fit a 10K NTC (Negative Temperature Coefficient) type thermistor between ‘TADJ’ and ‘GND’. This will set the threshold temperature to ~90ºC. Thermal control by LED current reduction Fig. 4 Thermal control The Thermal Control feature can be disabled by connecting ‘TADJ’ to ‘REF’ through the jumper resistor R8. Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 5 ZXLD1370EV1 BOARD LAYOUT Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 6 ZXLD1370EV1 INTENTIONALLY BLANK Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 7 ZXLD1370EV1 DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD 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 liability arising 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. 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Hillcrest Drive Westlake Village, CA 91362-3154 Tel: (+1) 805 446 4800 Fax: (+1) 805 446 4850 Kustermannpark Balanstraße 59, D-81541 München Germany Tel: (+49) 894 549 490 Fax: (+49) 894 549 4949 7F, No. 50, Min Chuan Road Hsin-Tien Taipei, Taiwan Tel: (+886) 289 146 000 Fax: (+886) 289 146 639 Rm. 606, No.1158 Changning Road Shanghai, China Tel: (+86) 215 241 4882 Fax (+86) 215 241 4891 Room A1103-04, ANLIAN Plaza, #4018 Jintian Road Futian CBD, Shenzhen, China Tel: (+86) 755 882 849 88 6 Floor, Changhwa B/D, 1005-5 Yeongtong-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do, Korea 443-813 Tel: (+82) 312 731 884 Fax: (+82) 312 731 885 Fax: (+86) 755 882 849 99 Issue 2 – Sept 2010 www.diodes.com © Diodes Incorporated 2010 8