STEVAL-ILL067V1

STEVAL-ILL067V1 Six-channel ALED7707-based LED driver with embedded boost converter for automotive interior lighting and TFT backlighting Data brief Description The purpose of this evaluation board is to provide an application example of a six-channel, mediumcurrent LED driver using the ALED7707 chip. The monolithic boost converter provides the required LED supply voltage starting from a single supply rail, while the brightness of the LED strings connected to the six outputs is controlled through a PWM signal. Open LED and LED short-circuit fault conditions are detected and managed. The board has been designed to provide a compact reference solution for automotive applications involving several LEDs arranged in multiple strings (e.g. interior lighting, infotainment LCD backlighting, etc.). Features         Wide DC input voltage (6 V - 32 V) Six 70 mA output channels (capable of 30 mA to 85 mA each) PWM brightness control (10 µs minimum dimming on-time) Up to 10 white LEDs per channel (36 V OVP threshold) > 90% efficiency (VIN=12 V, VBOOST=30 V, fSW =1 MHz, no snubber) On-board input filter for conducted EMI reduction RoHS compliant All automotive-grade components June 2015 DocID027964 Rev 1 For further information contact your local STMicroelectronics sales office 1/10 www.st.com Board description and efficiency measurement 1 STEVAL-ILL067V1 Board description and efficiency measurement Figure 1: Basic connection of the STEVAL-ILL067V1 evaluation board + - GSPG10062015DI1514 For a quick evaluation of the STEVAL-ILL067V1 performance, just connect a DC power supply (e.g. 12 V & 3 A current capability) between the VIN (J1) and GND (J2) terminals and a set of suitable LED strings between the VBOOST (J3) & ROW1-ROW6 (J10 through J15) terminals. The SW1 & SW2 jumpers should be both set in the lower postion, while the SW4 jumper should be in the right position (FSW & MODE pins forced high, DIM pin high, see Table 3 for details) as per default setting. As soon as the supply input is powered, the EN pin (floating) is internally pulled-up, a soft-start sequence takes place and the LED strings are powered at full-brightness. By pressing SW3 (EN pin tied low), the device shutsdown. This pushbutton allows to easily reset the device in case a latched turn-off occurs as 2/10 DocID027964 Rev 1 STEVAL-ILL067V1 Board description and efficiency measurement a consequence of a faulty condition (LED short-circuit, open string). To evaluate the PWM dimming capability, simply connect a pulse generator between the DIM terminal and ground (see figure 1) and remove the SW4 jumper to avoid any conflict between the external PWM signal and the +5 V rail. The frequency of the PWM signal should be in the 100 Hz - 20 kHz range, with a 10us minimum pulse duration and a 3.0 V to 5 V amplitude. Figure 2: STEVAL-ILL067V1 evaluation board PCB, top view DocID027964 Rev 1 3/10 Board description and efficiency measurement STEVAL-ILL067V1 Figure 3: STEVAL-ILL067V1 evaluation board PCB, bottom view Table 1: STEVAL-ILL067V1 connectors 4/10 Connector Name Function J1 VIN+ Power supply input, positive terminal J2 GND Ground. This terminal has to be preferred as return for the power supply input. J3 VBOOST Boost converter output. Connect this terminal to the common anode of the LED strings to be driven. J4 GND Quiet ground terminal. To be used as reference ground for all control signals. J5 SYNC Switching frequency synchronization output. A synchronization clock is available at this pin. J6 FAULT Faulty condition indicator. Open drain output, tied low by the device when a faulty condition is detected. Also used to drive the D2 LED. J7 DIM PWM dimming control input. The output current generators are activated according to this pin to perform a PWM brightness control of the LEDs. J8 EN Device Enable input. Internally pulled-up. If tied low the device turns-off. J9 FSW J10 ROW1 Switching frequency synchronization input. An external clock (30% max duty-cycle) can be provided at this terminal to synchronize the boost converter. J11 ROW2 J12 ROW3 J13 ROW4 Output terminals (channels). A low-side current generator is connected to each output. Connect to the kathode of the LED strings. Unused channels can be left floating. DocID027964 Rev 1 STEVAL-ILL067V1 Board description and efficiency measurement Connector Name J14 ROW5 J15 ROW6 Function Table 2: STEVAL-ILL067V1 test points Test point Function AVCC +5 V LDO output monitor (device supply rail). COMP COMP pin monitor (output of the trans-conductance amplifier of the control loop). Table 3: STEVAL-ILL067V1 jumpers and switches Jumper / switch Function SW1 FSW pin assignment. When the jumper is set in the upper position (FSW to R5), the switching frequency of the boost converter is set by R5 (1 MHz). In the lower position (FSW to VCC), the FSW pin is tied high and the 630 kHz fixed switching frequency is set. In case an external synchronization clock has to be applied at the FSW pin, this jumper must be in the upper position. SW2 MODE pin setting. This jumper allows to set high (VCC) or low (GND) the MODE pin in order to select the desired LED fault management. I case some channels are not used, the MODE pin must be set high. SW3 EN low pushbutton. When pressed the EN pin (internally pulled-up) is tied to ground. Used to restart the device in case a latched turn-off due to a faulty condition. SW4 DIM pin setting. If the jumper is set in the right position (VCC), the DIM pin is held high and the LEDs are driven at full-brightness as soon as the EN pin goes high. If the jumper is set in the left position (D3), the EN pin is pulled-down by R12 and activated by the PWM signal applied at the DIM pin through D3. This way a single-wire control is achieved (automatic device turn-on as soon as PWM dimming is applied). Note:D3 (BAT54K) & R12 (220k) are natively not mounted. DocID027964 Rev 1 5/10 Board description and efficiency measurement STEVAL-ILL067V1 Figure 4: STEVAL-ILL067V1 efficiency (fsw=1 MHz) GSPG10062015DI1530 92 Vin=8V 91 Vin=10V Vin=12V 90 Vin=14V Vin=16V Efficiency 89 88 87 86 85 84 83 82 10 12 14 16 18 20 22 24 26 Output voltage (V) 6/10 DocID027964 Rev 1 28 30 32 34 36 STEVAL-ILL067V1 Board description and efficiency measurement Figure 5: STEVAL-ILL067V1 efficiency with and w/o the R13-C14 snubber (fsw=1 MHz) GSPG10062015DI1535 94 92 Efficiency 90 88 86 Vin=8V Vin=12V Vin=16V 84 Vin=8V no snubber Vin=12V no snubber Vin=16V no snubber 82 10 12 14 16 18 20 22 24 26 28 30 32 34 36 Output voltage (V) DocID027964 Rev 1 7/10 DocID027964 Rev 1 GND EN DIM FAULT J2 J8 J7 J6 100k R 10 EN _LOW SW 3 D2 F AU LT LED DI M D3 4n7 C 16 N. M. R9 100k SW 4 1k R 11 AV C C AV C C N. M. R 12 MO D E SW 2 C O MP 4n7 C7 2k 4 R3 1 21 5 20 22 7 ALED7707 C9 R6 26 k 1 R7 180k TH PD R OW 1 R OW 2 R OW 3 R OW 4 R OW 5 R OW 6 PG N D SLOPE OVSEL 25 11 12 13 14 15 16 17 9 18 R2 18k R1 560k L8 L7 0R 6 0R 6 0R 6 0R 6 L5 L6 0R 6 0R 6 L4 L3 C 15 220p R8 680k C 20 220p C 19 220p C 18 220p 10u 10u C 17 C 11 C 10 FSW 390k 3n3 220p C 22 220p C 21 R5 C O MP EN MO D E DI M F AU LT LD O5 AV C C U1 R 13 8R 2 470p C 14 STPS1L40-Y 100p F SW SW 1 R4 4R 7 6 XAL7030-103 D1 220p J9 AV C C 470n 470n 24 C8 C5 C6 AV C C AV C C C4 10u SY N C F SW C3 10u 23 4 C2 47u SS J5 XAL5030-102 VIN RI LI M SYNC C1 100n 8 2 L2 19 L1 BI LI M J1 LX SG N D 8/10 3 10u C 12 100n C 13 J 15 J 14 J 13 J 12 J 11 J 10 J4 J3 ROW6 ROW5 ROW4 ROW3 ROW2 ROW1 GND VBOOST 2 10 VIN Schematic diagram STEVAL-ILL067V1 Schematic diagram Figure 6: STEVAL-ILL067V1 circuit schematic STEVAL-ILL067V1 3 Revision history Revision history Table 4: Document revision history Date Version 12-Jun-2015 Changes 1 DocID027964 Rev 1 Initial release. 9/10 STEVAL-ILL067V1 IMPORTANT NOTICE – PLEASE READ CAREFULLY STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers’ products. No license, express or implied, to any intellectual property right is granted by ST herein. Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product. ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners. Information in this document supersedes and replaces information previously supplied in any prior versions of this document. © 2015 STMicroelectronics – All rights reserved 10/10 DocID027964 Rev 1