IS31LT V, 350MA, 4-CHANNEL CONSTANT CURRENT REGULATOR WITH OTP

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1 IS3LT37 53V, 35MA, 4-CHANNEL DESCRIPTION The IS3LT37 is a 4-channel, linear regulated, constant current LED driver which can sink 4 equal currents of up to 35mA per channel to drive high brightness LEDs over an input voltage range of 6V to 53V, while maintaining an output leakage current of less than ua. The sink current is easily programmed using a single external resistor. The current sinks of the IS3LT37 may be connected in parallel to allow greater than 35mA of LED current, i.e., all four VLEDx pins tied together for a maximum.4a sink available for one LED string. See limitations in the LED CURRENT SETTING section The IS3LT37 also features a PWM input to enable simple dimming control using a digital control signal The IS3LT37 features an optional.5v reference voltage output capable of supplying up to ma (typ.). This voltage may be used to drive the base of external BJTs for high current applications which are driven by a widely varying input voltage FEATURES 6V to 53V input supply voltage range Up to.4a total sink current Over temperature protections Thermal current regulation above 3 C Sink current matching 3% between channels PWM dimming and Shutdown control input Optional.5V output to drive external standoff BJTs Very few external components QUICK START Figure : Photo of IS3LT37-EBBJT Evaluation Board RECOMMENDED EQUIPMENT 6.V~53V, A DC power supply One digital voltmeter Four series-connected HB LED strings rated no less than 35mA A current probe to measure the HB LED current ABSOLUTE MAXIMUM RATINGS 53V power supply Caution: Do not exceed the conditions listed above, otherwise the board will be damaged. EVALUATION BOARD OPERATION The evaluation board can be configured to operate in one of two current level modes. The device input current is controlled by switch (S), when S is pushed UP, <With BJT> mode, the HBLED string current at VLEDx pin is set to 35mA, when S is pushed DOWN, <Without BJT> mode, the HBLED string current is set to ma. The operating current (35mA or ma) is set by S switch selection of a resistor value at IS3LT37 pin 8. See LED CURRENT SETTING section of the datasheet for guidance in calculating resistor values for specific currents. PROCEDURE The IS3LT37 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. ) Verify that the S is pushed UP to select <With BJT> mode. ) Connect each HBLED string as follows: CHx: Connect the HBLED string cathode to the CHx of CON3 and the anode to on CON Where x is,, 3 and 4. Unused CHx inputs should be connected to GND 3) Calculate the, recommended value is V to V higher than the sum of the LED string s total forward voltage drop. For example, if the LED string s total forward voltage is V@35mA (three LEDs with 3.33V forward voltage drop each), the recommended is V to V. Note: Selecting an input voltage much higher than the LED string s total forward voltage will cause power dissipation on the on board BJTs (Q Q4). 4) Insert the current probe between the CHx terminal (CON3) and the cathode of the CHx LED string to measure the HBLED current. Integrated Silicon Solution, Inc. Rev. B, 7/6/4

2 IS3LT37 53V, 35MA, 4-CHANNEL 5) JP is used to configure the PWM signal input mode. When JP is ON the IS3LT37 is enabled and no external PWM signal should be connected. When JP is OFF the IS3LT37 must be driven by an external PWM signal source. Caution: Always remove JP when driving the IS3LT37 with an external PWM source. JP ON pulls up the TP pin to a possibly high voltage that may damage the PWM signal source. 6) Turn on the power supply () and measure the HBLED current using the current probe and verify all channels (CHx). 7) Slide S down to select <Without BJT> mode. 8) Measure the HBLED current using the current probe and verify all channels (CHx). POWER SUPPLY AND POWER DISSIPATION The dissipation is proportional to the voltage across the LED and the sink current that can be defined as: P L EDx V LEDS x I Where x is,, 3 or 4. V LEDSx is the total forward voltage of LEDs in series, I is the current of the LED series. When working with BJT (S UP), P P BJTx 37 ( V V V ) I 4 ( V x VLEDx VLEDx I LEDSx ) V I Where x is,, 3 or 4. V VLEDx is the voltage of the IS3LT37 VLEDx pin (Headroom voltage), see Equation (3) of the datasheet for guidance in calculating the V VLEDx. I is the current of the LED series, I Q is the operation current of IS3LT37 and Q5. Assume I =35mA, V LEDSx =V, V =V, I Q =8mA, V VLEDx =.4V. P LEDx =V.35A=3.5W P BJTx =(V-V-.4V).35A=.56W P 37 =.4V.35A 4+V.8A=.58W Caution: If is much higher than V LEDSx, then verify that P BJTx <.5W for all conditions. When working without BJT (S DOWN), 4 P37 ( V x 4 ( V x VLEDx LEDSx I V Rx ) I ) V I ) V Q Q I Where x is,, 3 or 4. V Rx is the voltage across Rx(x=5 to 8), V LEDSx is the total forward voltage of LEDs in series, see Figure for details. Q The voltage at VLEDx pin of the IS3LT37 will be the remaining value of V -V -V Rx, and if it is larger than.8v@35ma,the IC dissipation will be high which may trigger the IC over temperature protection (OTP). Assume V =V, I =ma, V LEDSx =9.V, Rx=4Ω, I Q =5mA. P LEDx =9.V.A=.9W P Rx =.A.A 4Ω=.4W P 37 =(V-(.A 4Ω) -9.V).A 4+V.5A =.3W LED CURRENT SETTING The maximum sink current of all four channels (VLEDx) is set by resistor (R ISET ) connected from the IS3LT37 I SET pin (8) to ground. The maximum possible current is 35mA per VLEDx pin, however, more than one VLEDx pin can be tied together to allow for larger currents. Two combined VLEDx pins will double the available sink current for the LED string, while combining all four VLEDx pins will result in 4x the sink current for one LED string. The VLEDx sink current can be calculated by the following; V ISET =.7V (typ): VISET I SINKx 6 RISET When S UP With BJT, R ISET =R//R, and S DOWN Without BJT, R ISET =R.For accurate LED current, resistors should be % or better tolerance. More information please refers to the IS3LT37 datasheet. HB LED DIGITAL-DIMMING CONTROL The JP connector is used for configuring the dimming function as in the table below: JP Configuration Description ON No external PWM signal OFF Connect external PWM signal source The evaluation board features a PWM input terminal for connecting an external digital PWM signal. JP connector is used to connect or disconnect a k ohm pull up resistor (R4) to the PWM input. Apply a digital PWM signal with a.8v logic-low (or less) and a.v logic high (or greater) level, and frequencies from 4kHz to khz. To adjust the HB LED brightness, vary the signal duty cycle from to. Caution: If JP is ON the PWM pin will be pulled up to the input which can be up to 53V. Integrated Silicon Solution, Inc. Rev. B, 7/6/4

3 IS3LT37 53V, 35MA, 4-CHANNEL ORDERING INFORMATION Part No. Temperature Range Package IS3LT37-ZLS4-EBBJT -4 C ~ +5 C (Industrial Range) etssop-6, Lead-free Table: Ordering Information For pricing, delivery, and ordering information, please contacts ISSI s analog marketing team at analog@issi.com or (48) R9.K/.5W C8 33uF/V GND C7 C6 uf/v.uf/v CON 3 R4 K U Vref VLED 9 6 Q5 PBSS46U R4 43 R3 43 MJD3 Q4 R8 R7 4R/W 4R/W S CON CH PWM TP JP VLED PWM VLED3 AGND AGND VLED4 PGND PGND Iset IS3LT37-EBBJT 4 8 R R C5 uf/v MJD3 MJD3 MJD3 C4 C3 C C nf/v nf/v nf/v nf/v Q3 Q Q R R3 R R R6 4R/W R5 4R/W K NC 6.K 9K SS-6H CH CH3 CH4 CON3 Figure : IS3LT37 Application Schematic Integrated Silicon Solution, Inc. 3 Rev. B, 7/6/4

4 IS3LT37 53V, 35MA, 4-CHANNEL BILL OF MATERIALS Name Symbol Description Qty Supplier Part No. LED Driver U Constant current LED driver ISSI IS3LT37 BJT Q~Q4 NPN power Transistor 4 ONSEMI MJD3 BJT Q5 6V/A NPN BISS Transistor NXP PBSS46U Resistors R~R4 RES, 43R,/6W,±5%,SMD 4 YAGEO RC85JR-743L Resistors R5~R8 RES, 4R,W,±5%,DIP 4 Resistor R9 RES,.K,.5W,±5%,DIP Resistor R RES, 6.K,/W,±%,SMD YAGEO RC85FR-76.KL Resistor R RES, 9K,/W,±%,SMD YAGEO RC85FR-79KL Resistor R RES, K,/W,±%,SMD YAGEO RC85FR-7KL Resistor R4 RES,K,/W,±5%,SMD YAGEO RC85JR-7KL Resistor R3 NC Capacitors C~C4 CAP,.µF,V,±%,SMD 4 YAGEO 85DKX7R6BB4 Capacitors C5 CAP, µf,v,±%,smd YAGEO 85DKX7R6BB5 Capacitor C6 CAP,.µF,V,±%,SMD YAGEO 6DKX7RBB4 Capacitor C7 CAP, µf,v,±%,smd Capacitor C8 CAP, 33µF,V,±%,SMD Switch S 6PT DIP Jumper JP.54mm Jumper Connector CON,CON DC connector Bill of materials, refer to Figure above. Integrated Silicon Solution, Inc. 4 Rev. B, 7/6/4

5 IS3LT37 53V, 35MA, 4-CHANNEL Figure 3: Board Component Placement Guide -Top Layer Figure 4: Board PCB Layout- Top Layer Integrated Silicon Solution, Inc. 5 Rev. B, 7/6/4

6 IS3LT37 53V, 35MA, 4-CHANNEL Figure 5: Board Component Placement Guide -Bottom Layer Figure 6: Board PCB Layout-Bottom Layer Copyright 4 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. 6 Rev. B, 7/6/4