Datasheet - Mouser Electronics
Contents
1. CAT4238 LED Current versus Input Voltage 10 LEDs in series 35 30 25 x 20 a 15 LLJ 10 5 0 3 00 3 50 4 00 4 50 5 00 5 50 Vin V Roet 29 82 E Rser 15Q9 Rgser 10Q Note Rser R1 R2 Figure 4 LED Current Line Regulation http onsemi com 3 CAT4238AEVB CAT4238 FB Voltage versus Input Voltage lLep 10mA E llep 20mA amp llep 30 mA 310 300 4 Vee mV N O O 3 00 3 50 4 00 4 50 5 00 5 50 Vin V Figure 5 Veg Voltage Line Regulation Efficiency Evaluation The efficiency is evaluated according to the following equation Teen X ZVFI Imn X Vin where VFi Vout Vep VLEDis the voltage measured on LED T10 test point Efficiency x 100 1 Insert a current meter CM1 between input supply voltage Vext and Vinpad to monitor the input current Im or use an embedded power supply current meter 2 Set the input voltage for Vin 3 6 V 3 Adjust the R2 potentiometer for the ILEp 5 mA Observe the ILep current on the meter CM2 inserted between Pin 1 and Pin 2 of J4 connector 4 Measure the lin current on CM1 5 Monitor the output voltage on Vout T7 and VLEp voltage on LED T10 test points 6 Repeat steps 3 to 5 for Ien 10 mA 15 mA 20 mA 25 mA and 30 mA Figure 6 shows the efficiency measured for 2 values of input voltage Vin 3 62. V and Vin 4 2 V with 10 LEDs in series connected to the CAT4238 output CAT4238 Efficiency 10 LEDs in series o Vin z3 6V Vin 4 2V 90 85 80 75 Efficiency 70 65 5 10 15 20 25 30 ILED mA Figure 6 CAT4238 Efficiency Driving 10 LEDs in Series Dimming Control The LED brightness control can be accomplished by using a PWM signal applied to the SHDN pin or to the FB pin The other method is to use a variable DC voltage applied through a resistor to FB pin 1 Dimming using a PWM signal on the SHDN pin The LEDs are turned off and on at the PWM frequency The average current changes with the duty cycle Increasing the duty cycle will increase the LED brightness The peak current value sets the light spectrum Connect the jumper shunt between Pin 2 and Pin 3 of the J1 connector e Apply a pulse signal generator to the GEN DC T3 pad Frequency 200 Hz to 2 kHz Amplitude 0 V to 3 V for ViIn 3 6 V e Modify the duty cycle between 0 and 100 Observe the average current through LEDs measured by a current meter inserted at J4 connector For 0 duty cycle the Itep will be off Itep OmA At the maximum duty cycle the LED will be driven at the maximum current set by the R2 potentiometer e Monitor the FB voltage compared with the PWM signal applied on SHDN input Figure 7 shows the voltage monitored on the FB pin Vrs CH2 using
3. the CAT4238 white LED driver Driving 10 LEDs in series and Shutdown Mode 1 Connect the 10 LED string to the CAT4238 output through J4 header pin connector 2 Set the R2 potentiometer to the middle position 3 Apply the external voltage supply Vext 3 0 V lt Vin lt 5 V between Vy T1 and GND T2 4 The CAT4238 is in the shutdown mode SHDN pin is connected to GND if the J1 connector Pin 1 Pin 2 is not jumpered Connect a current meter between Vext and Vry pad to measure the shutdown current Isp lt lt 1 uA n this mode of operation the LEDs are disconnected from the output LEDs are OFF 5 Connect SHDN pin of CAT4238 to VIN using a jumper shunt between Pin 1 and Pin 2 of J1 connector Observe that LEDs are ON LED Current Evaluation 1 Programming LED current LED current is programmed using the external resistors RSET R1 R2 connected to the FB pin The voltage at the FB pin is internally regulated to the value Vrs 300 mV 15 mV The current into the LED pin can be set according to the following equation Vre mV Vee lieo mA RI R2 RSET Q Set the input voltage ex Vm 3 6 V Disconnect the jumper from the J4 connector and insert a current meter between these pins to monitor the LED current ILED Rotate the potentiometer R2 and observe the Iep value on the current meter The current can be adjusted between 3 mA and 30 mA approximately Various LED current values and the ass
4. 238AGEVB
5. CAT4238AEVB CAT4238 10 LED Boost Converter Evaluation Board User s Manual Introduction This document describes the CAT4238AGEVB Evaluation Board for the ON Semiconductor CAT4238 High Efficiency 10 LED Boost Converter The functionality and major parameters of the CAT4238 can be evaluated with the CAT4238AGEVB board The CAT4238 is a high voltage CMOS constant current DC DC converter that has been designed to drive with high efficiency white or other high brightness LEDs The high voltage output stage allows driving up to 10 white LEDs in series A single external resistor sets the LED current between 5mA and 40 mA LED current can be adjusted using either a pulse width modulated PWM signal or a DC voltage Detailed descriptions and electrical characteristics are in the CAT4238 data sheet T1 VIN Q T2 GND mL O T3 GEN DC T4 GND O T5 FB O T6 SGND OST ON Semiconductor http onsemi com EVAL BOARD USER S MANUAL CAT4237EVAL2 Board Hardware The evaluation board contains a CAT4238 DC DC boost converter in a typical application circuit As configured the board circuit is set to drive up to 10 white LEDs in series The user can chose to connect the CAT4238 output to the on board LEDs string or to an external LEDs string from an application The board provides the option to connect a different number of LEDs available on board 8 9 or 10 using a jumper shunt for one of the J2 to J4 connecto
6. a PWM signal applied to the SHDN pin CH1 The frequency of the PWM signal is 2 kHz approximately Test Conditions PWM on SHOH VIH 3 67 ILED on 20hmA TRIGGER SETUP trigger on D234 ext Extl Line coupling 1 iE AC LFREJ HFREJ HF slope 1 neo holdoFF z Tire Ewts 1 2 Y OC amp dt 59 42 ps ky 16 829 kHz H l0 mw OC 50 MGs 20 mV AC 1 OC 0 88 v 4 50 mY AC 0 AUTO ev OP CH VFB VC mi e DVI Figure 7 FB Voltage Waveform with PWM 2 Dimming using a DC voltage applied to the FB pin TA variable external DC voltage is applied on FB pin to adjust the LED current As the DC voltage is increased the voltage drop on resistor R3 is increased and the voltage drop on RSET R1 R2 is decreased thus the LED current decreases The external DC voltage is applied to FB pin through a series resistor R5 which sets the maximum DC voltage http onsemi com CAT4238AEVB Also a filtered PWM signal can be considered as a e Apply the variable DC voltage between GEN DC T3 variable DC voltage and GND T4 Connect the SHDN pin to Vin jumper shunt between Increase the DC voltage value from 0V to Pin 1 and Pin 2 of J1 connector Vmax 3 2 V Set the ILep current i e ILEp Max 20 mA Observe the Itep current decreases from the ILED Max J Connect the GEN DC to FB pin through R5 resistor using one jumper between Pin 3 and Pin 4 and
7. another jumper shunt between Pin 5 and Pin 6 of J1 20mA previous set to lep mn OmA for Vmax 3 2 V with the existing resistors values R3 1 KQ R5 10 KQ connector ON Semiconductor and ON are registered trademarks of Semiconductor Components Industries LLC SCILLC SCILLC reserves the right to make changes without further notice to any products herein SCILLC makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does SCILLC assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation special consequential or incidental damages Typical parameters which may be provided in SCILLC data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts SCILLC does not convey any license under its patent rights nor the rights of others SCILLC products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur Should Buyer purchase or us
8. e SCILLC products for any such unintended or unauthorized application Buyer shall indemnify and hold SCILLC and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part SCILLC is an Equal Opportunity Affirmative Action Employer This literature is subject to all applicable copyright laws and is not for resale in any manner PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT Literature Distribution Center for ON Semiconductor P O Box 5163 Denver Colorado 80217 USA Phone 303 675 2175 or 800 344 3860 Toll Free USA Canada Fax 303 675 2176 or 800 344 3867 Toll Free USA Canada Email orderlit onsemi com N American Technical Support 800 282 9855 Toll Free ON Semiconductor Website www onsemi com USA Canada Europe Middle East and Africa Technical Support Phone 421 33 790 2910 Japan Customer Focus Center Phone 81 3 5773 3850 Order Literature http www onsemi com orderlit For additional information please contact your local Sales Representative EVBUM2019 D Mouser Electronics Authorized Distributor Click to View Pricing Inventory Delivery amp Lifecycle Information ON Semiconductor CAT4
9. nal applied DC voltage on the FB pin The ON OFF operation and dimming control can be selected using the jumper options for the J1 connector Test points T1 to T10 are available to apply the external voltages signal generator or to measure the output voltages signals provided by CAT4238 The component placement is shown in Figure 2 Table 1 presents the component list for this evaluation board CATS4236 White LED Driver CAT4238EVALI Rev 1 0 fe vourd ran B VIN 2 MBER n N Sie s ae si a 7 Se Tj oA MME en ER Eo 4 A san TS LED a2 or CAT4238 i sang CATALYST www Catsemi com 408 542 1000 GND GND Te 72K Figure 2 CAT4238AEVB Board Table 1 CAT4238AGEVB BOARD LIST OF COMPONENTS Trimmer Pot 1 4 100 Q Not Soldered on Board n J2 to J4 2 pin Header Connector 0 1 Single Strip optional T1 to T10 Pin Receptacle Test Points Description CMOS White LED Driver TSOT23 5pin or Panasonic or Digi Key PCC2315CT ND or Kemet Digi Key 587 1287 1 ND or CDR6D23MN 470 Part Number CAT4238TD G 1 3329W 101 ND or equiv 10 1 3 ND iv Digi_ Key 1012 02 ND or equiv 0149 0 15 01 30 14 04 0 or equiv 10 oo k Ea http onsemi com CAT4238AEVB CAT4238 EVALUATION The CAT4238AGEVB gives the user a way to evaluate the CAT4238 in a typical application of driving multiple LEDs The following steps are an example of how the user can evaluate
10. ociated RSET values are listed below e Monitor the voltage on FB T5 Vout T7 and SW T9 e Verify the internal switch frequency fsw 1 0 MHz typically using a scope probe connected on SW T9 test point GND T8 Figure 3 shows the internal switch output Vsw DC coupled 5 V div and the regulated voltage on FB pin Vrs DC 500 mV div for Vin 3 6 V ILep 20 mA 10 LEDs in series connected to the CAT4238 output 23 Oct 86 Test Conditions VIH 34V LED tna 10 LEDs m s rias 17 16 01 TRIGGER SETUP 19 6 v ad 6 54 V gt p trigger on 8 58 D2 3 4 Ext 54 mi Extl Line l coupling Leg HF REJ Heo CH2 VFB slope 1 L IE eo ho ldo FF 5 ps BL a ime Ev ts 1 V Og At 1 633 ps W 968 1 kie Sa mv OC 500 M s 1 YV Dg i 1 OC 18 8 w Bom SO f oO de WORE m 1B AUTO Figure 3 Internal Switch Output and Regulated Vrs Voltage Waveforms lLep 20 mA Vin 3 6 V 2 Evaluating LED current regulation versus the input voltage VIN Set the Itep to a programmed value using the R2 potentiometer i e 10mA 20mA 30mA for Vin 3 6 V For any Itep value vary the Vin voltage between 3 0 V and 5 5 V Observe the value of ILep measured by the current meter and Vrs using a voltmeter Figure 4 presents the ILep current versus Vin Figure 5 shows the CAT4238 FB voltage versus input voltage
11. rs The board schematic is shown in Figure 1 VOUT T8 OT7 GND PA LED YA Lo yf L3 yA L4 A L5 L A L6 A L7 jo y lank A L10 J3 J4 Figure 1 CAT4238AEVB Board Schematic Semiconductor Components Industries LLC 2011 September 2011 Rev 3 Publication Order Number EVBUM2019 D CAT4238AEVB The board is powered from an external voltage applied to the Vij T1 pad The circuit is delivered with no LEDs soldered on board The user can solder his white LEDs on the CAT4138 board 8 to 10 LED string pads layout provided or he can choose to connect the LEDs from his application between Vout T7 and LED T10 test points The LED current is set through the external resistors connected to the FB pin R1 R2 Using the variable resistor R2 the LED current can be set from 3 mA to 40 mA Most white LEDs are driven at a maximum current between 15 mA and 20 mA to ensure a pure white light The board also demonstrates the CAT4238 shutdown mode and LED brightness control by using an external CAT4236 White LED Driver CAT423HEVAL1 Rev 1 0 Lit LzL__ LiL_ La _ e LaL__ vouT TT GND TH LEL ely LI a l Lio faa i Llo E le FS TL LED pe O CAT eal YY ST WaWwW Catsemi com 408 342 1000 CAT4238 SGND T PWM signal or a DC voltage Resistors R3 and R5 R5 soldered on board by the user are used to adjust the LED current using the dimming control with an exter
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