IS32LT3175N/P SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT AND PWM DIMMING DESCRIPTION FEATURES The IS32LT3175 is a single channel linear Operating voltage 5V to 42V programmable current regulator capable of up to Single channel current source 150mA. It integrates a debounce and latch circuit on - Programmable current via a single external the channel enable pin (EN) to facilitate the use of a resistor low cost momentary contact switch. The PWM pin can - Configurable from 20mA to 150mA be interfaced to a logic level courtesy light signal to Momentary contact button EN input directly drive the LED channel. The IS32LT3175P - Input is debounced and latched accepts a positive polarity PWM signal while the - Higher priority than PWM input IS32LT3175N accepts a negative polarity PWM signal. - Gamma corrected Fade In/Out algorithm The device operates as a stand-alone LED driver - Pull down resistors set independent fade IN and configurable with external resistors no microcontroller OUT ramp time is required. A single external resistor programs the PWM input pin driven by external PWM source current level, while two separate resistors - PWM directly drives the current source independently program the fade in and fade out ramp - IS32LT3175P Positive polarity rate for the channel. - IS32LT3175N Negative polarity The device integrates a 63 steps fade in and fade out Fault Protection: algorithm (Gamma correction) which causes the output - OUT pin shorted to GND LED current to gradually ramp up to the full source - ISET pin shorted to GND value after the EN pin is pulsed. The same controller - Over temperature causes the LED current to gradually ramp down to zero if the EN pin is pulsed while the output channel is SOP-8-EP package ON. The fade ramp can be interrupted mid-cycle Automotive Grade - AEC-Q100 before completion of the ramp cycle. The EN pin will Operating temperature range from -40C ~ +125C accept either a momentary contact switch or logic level signal pulsed low. RECOMMENDED EQUIPMENT The IS32LT3175 is targeted at the automotive market with end applications to include map and dome lighting 12V,1A DC power supply as well as exterior accent lighting. For 12V automotive applications the low dropout driver can support 1 to 3 LEDs (V = 3.2V) per channel. F ABSOLUTE MAXIMUM RATINGS 42V power supply QUICK START Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. PROCEDURE The IS32LT3175N/P 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 V supply should be set close to the CC IS32LT3175N/P minimal headroom voltage of 0.9V (VCC Voutx) for best thermal performance. The board can be operated with a larger headroom voltage as long as the Figure 1: Photo of IS32LT3175N/P Evaluation Board increase in package temperature is monitored. Exceeding the device package temperature specification will cause the device to enter thermal protection mode. 2) The output current of is adjusted by the variable resistor (RW1). Turn RW1 counter clockwise to decrease the output current and clockwise to increase the output current. The test point ISET can be used to detect the resistor value at the ISET pin. The final resistance can be measured Lumissil Microsystems www.lumissil.com 1 Rev. C, 08/11/2021 IS32LT3175N/P SINGLE CHANNEL LINEAR LED DRIVER WITH FADE IN/FADE OUT AND PWM DIMMING with an ohm meter across ISET and GND pins. enable/disable the Output LED. Press K1 to Use this measured resistor value to replace the change the state of the onboard LED string variable resistor RW1 and R1 (see schematic anytime, even though the fade time doesnt Figure 2). complete. 3) The fade in time is adjusted by the variable 6) JP1 is used to connect the IS32LT3175N/P resistor (RW2). Turn RW2 counter clockwise to Output (pin6) to the onboard LED string decrease fade in time, and clockwise to increase (LED1~LED3). Use one of the green terminal fade in time. Once the desired fade in time is set, blocks to connect an external LED string. Remove measure the resistor value across TSET UP and the corresponding jumper header (JP1) to disable GND. Use this measured resistor value to replace the onboard LED string. Note: Connecting an external LED string without the variable resistor RW2 and R2 (see schematic removing the onboard string jumper header will drive both Figure 2). onboard and external LED strings in parallel resulting in 4) The fade out time is adjusted by the variable lower current drive to the LED string. resistor (RW3). Turn RW3 counter clockwise to 7) The on board LED string size can be adjusted decrease fade out time, and clockwise to increase from 1 to 3 LEDs by using jumper headers fade out time. Once the desired fade out time is JP2~JP3. Connecting the header to pins 2-3 set, measure the resistor value across TSET DN disables the corresponding LED, ie JP2 pins 2-3 and GND. Use this measured resistor value to disables LED2. To enable all the LED1~LED3 replace the variable resistor RW3 and R3 (see connect JP2~JP3 to pins 1-2. schematic Figure 2). 5) Momentary contact buttons (K1) is used to ORDERING INFORMATION Part No. Temperature Range Package IS32LT3175P-GRLA3-EB -40C ~ +125C (Automotive) SOP-8-EP, Lead-free IS32LT3175N-GRLA3-EB Table 1: Ordering Information For pricing, delivery, and ordering information, please contact Lumissils analog marketing team at analog Lumissil.com or (408) 969-6600. EVALUATION BOARD OPERATION If either the TSET UP or TSET DN pin is tied directly to GND, the corresponding fade function is canceled IS32LT3175N/P evaluation board drives one string of and the ramp time is about 70s, or instant on. WLEDs. There are three variable resistors used for However, the debounce feature of the EN pin is not adjusting the LED current (RW1), fade in time (RW2), disabled. fade out time (RW3). OUTPUT CURRENT SETTING SETTING THE FADE TIME A single programming resistor (R ) controls the ISET The fade time is set by two external programming maximum output current for the output channel resistors R and R . The R TSET UP TSET DN TSET UP simultaneously. The programming resistor may be connected to the TSET UP pin configures the fade computed using the following Equation: ramp ON time while the RTSET DN connected to the TSET DN pin configures the fade ramp out time. The 1500 R (10kR 75k) ISET fade time (In or Out) is programmable by Equation (2): ISET I SET t R 2.5 s (2) TSET The device is protected from an output over current condition caused by an accidental short circuit of the For example, R =100k, Fade In/Out time is about TSET ISET pin, by internally limiting the maximum current in 0.25s. the event of an ISET short circuit to 205mA. Note: In order to get the optimized effect, the recommended fading time is between 1.5s (RTSET= 600k) and 0.25s (R = 100k). TSET Lumissil Microsystems www.lumissil.com 2 Rev. C, 08/11/2021