IS32LT3174 SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT DESCRIPTION RECOMMENDED EQUIPMENT The IS32LT3174 is a linear programmable current regulator consisting of one output channel capable of up to 200mA. It features an ON/OFF input pin to toggle the channel between the OFF condition and the source condition. The device integrates 63 steps fade in and fade out algorithm (Gamma correction) which causes the output LED current to gradually ramp up to the full source value after the channel’s control pin is pulsed. The same controller causes the LED current to gradually ramp down to zero if the channel’s input control pin is pulsed while the output channel is on. FEATURES Output current can source up to 200mA Independent debounced ON/OFF control for channel Programmable current via a single external resistor Programmable fade in, fade out via external resistor - Pull down resistor value sets fade speed - Gamma corrected fade in/out algorithm Fault protection: - LED string shorted to GND - Over temperature SOP-8-EP packages Automotive grade - AEC-Q100 (pending) Operating temperature range from -40°C ~ +125°C ABSOLUTE MAXIMUM RATINGS PROCEDURE The IS32LT3174 evaluation board is fully assembled and tested. Follow the steps listed below to verify board operation. Caution: Do not turn on the power supply until all connections are completed. 1) Connect the ground terminal of the power supply to the GND and the positive terminal to the VCC. Note: The VCC supply should be set close to the IS32LT3174 minimal headroom voltage of 0.5V (VCC – Voutx) for best thermal performance. The board can be operated with a larger headroom voltage as long as the increase in package temperature is monitored. Exceeding the device package temperature specification will cause the device to enter thermal protection mode. 2) 3) 4) 5) Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 06/29/2015 ≤ 45V power supply Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. QUICK START Figure 1: Photo of IS32LT3174 Evaluation Board 12V,1A DC power supply The fade time is adjusted by the variable resistor (RW1). Turn RW1 counter clockwise to decrease fade time, and clockwise to increase fade time. Once the desired fade time is set, measure the resistor value across TP1 and GND. Use this measured resistor value to replace the variable resistor RW1 and R3 (see schematic Figure 2). The output current is adjusted by the variable resistor (RW2). Turn RW2 counter clockwise to decrease the output current, and clockwise to increase the output current. The test point TP2 can be used to detect the resistor value at the ISET pin. The final resistance can be measured with an ohm meter across TP2 and GND pins. Use this measured resistor value to replace the variable resistor RW2 and R4 (see schematic Figure 2). Momentary contact buttons (K1) are used to enable/disable the Out LED channel. Press K1 to enable the onboard LED string for channel 1. JP1 is used to connect the IS32LT3174 Out to the onboard LED string (LED1, LED3 and LED5). Use one of the green terminal blocks to connect an external LED string. Remove the jumper header (JP1) to disable the onboard LED string. Note: Connecting an external LED string without removing the onboard string jumper header will drive both onboard and external LED strings in parallel resulting in lower current drive to both strings. 1 IS32LT3174 SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT 6) The on board LED string size can be adjusted from 1 to 3 LEDs by using jumper headers (JP1, JP3, JP5). Connecting the header to pins 2-3 disables the corresponding LED, ie JP3 pins 2-3 disables LED5. To enable all the LEDs, connect all jumper to pins 1-2. . ORDERING INFORMATION Part No. Temperature Range Package IS32LT3174-GRLA3-EB -40°C ~ +125°C (Automotive) SOP-8-EP, Lead-free Table 1: Ordering Information For pricing, delivery, and ordering information, please contact ISSI’s analog marketing team at [email protected] or (408) 969-6600. EVALUATION BOARD OPERATION IS32LT3174 evaluation board drives one string of WLEDs. There are two variable resistors used for adjusting the fade time (RW1), LED current (RW2). THERMAL ROLLOFF SETTING THE FADE TIME The fade time, either in or out, is the same, and is set by a single external programming resistor (RTSET). The fade time is programmable by Equation (1): t RTSET 2.5s (1) For example, RTSET=100kΩ, fade time is about 0.25s. Note: In order to get the optimized effect, the recommended fading time is between 1.5s (RTSET=600kΩ) and 0.25s (RTSET=100kΩ). If the TSET pin is tied directly to GND, the fade in/out function is canceled and the ramp time is about 73µs, or ‘instant on’. However, the debounce feature of the ENx pin is not disabled. OUTPUT CURRENT SETTING A single programming resistor (RISET) controls the maximum output current. The programming resistor may be computed using the following Equation: RISET The device is protected from an output over current condition caused by an accidental short circuit of the ISET pin, by internally limiting the maximum current in the event of an ISET short circuit to 260mA. 2000 (10kΩ≤RISET≤100kΩ) I SET Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 06/29/2015 The output current will be equal to the set value so long as the die temperature of the IC remains below 125°C (Typical). If the die temperature exceeds this threshold, the output current of the device will begin to reduce at a rate of 3%/°C. The roll off slope is related to ISET value. When ISET=20mA, the roll off slope is about 3.7%. When ISET=200mA, the roll off slope is about 2.2% FAULT DETECTION An output shorted to GND fault is detected if the output voltage on a channel drops below the low voltage threshold VSCD and remains below the threshold for tFD. The short condition will reduce its output current to 20% of ISET. When short condition is removed, output current will recover to original value. When output current is larger than limit value, about 260mA, the output current will be clamped. When the open fault condition is recovered, there will be a large current pulse about 10µs. 2 IS32LT3174 SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT GND OUT1 2 VCC 1 GND 2 1 VCC C6 47uF/63V VCC U1 6 C3 C4 C5 1uF 1uF 0.1uF JP1 Close =Internal LED JP1 JP1 Open =External LED VCC OUT OUT1 K1 NC R1 0R 8 7 C1 4 5 EN LED1 NC NC 1 2 R3 100K R4 10K RW1 1 TSET GND 3 2 ISET 3 LED3 IS32LT3174 0~500K RW2 JP3 1 TP1 2 LED5 0~100K 3 JP5 TP2 Figure 2: IS32LT3174 Application Schematic BILL OF MATERIALS Name Symbol LED Driver U1 Resistor Description Qty Supplier Part No. LED Driver 1 ISSI IS32LT3174 R3 RES,100k,1/8W,±1%,SMD 1 YAGEO RC1206FR-07100KL Resistor R4 RES,10k,1/8W,±1%,SMD 1 YAGEO RC1206FR-0710KL Resistor R1 RES,0ohm,1/16W,±5%,SMD 1 YAGEO RL0603JR-0700RL Variable Resistor RW1 RES,0~500K 1 Variable Resistor RW2 RES,0~100K 1 Capacitor C6 CAP,47µF,63V,±20%,SMD 1 Capacitor C5 CAP,0.1µF,50V,±10%,SMD 1 YAGEO CC0603JKX7R9BB104 Capacitor C3,C4 CAP, 1µF,50V,±10%,SMD 2 YAGEO CC0805JKX7R9BB105 Button K1 Momentary Button SMD 1 Terminal blocks OUT1 green terminal blocks 1 Bill of materials, refer to Figure 2 above. Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 06/29/2015 3 IS32LT3174 SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT 0 0 2 1 1 2 9 10 8 1 7 0 0 6 1 3 5 1 2 1 1 1 1 1 1 1 4 3 2 1 4 4 9 10 8 1 7 0 0 3 3 2 3 6 3 4 2 3 5 4 4 3 0 1 2 0 1 2 2 1 0 0 0 0 9 10 8 1 7 0 0 6 2 3 5 4 0 0 0 Figure 3: Board Component Placement Guide - Top Layer Figure 4: Board PCB Layout - Top Layer Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 06/29/2015 4 IS32LT3174 SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT 0 0 2 1 1 2 9 10 8 1 7 0 0 6 1 3 5 1 2 1 1 1 1 1 1 1 4 3 2 1 4 4 9 10 8 1 7 0 0 3 3 2 3 3 4 6 2 3 5 4 4 3 0 1 2 0 1 2 2 1 0 0 0 0 9 10 8 1 7 0 0 6 2 3 5 4 0 0 0 Figure 5: Board Component Placement Guide - Bottom Layer Figure 6: Board PCB Layout - Bottom Layer Copyright © 2015 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products. Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that: a.) the risk of injury or damage has been minimized; b.) the user assume all such risks; and c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances Integrated Silicon Solution, Inc. – www.issi.com Rev. A, 06/29/2015 5