CAT4238AEVB

CAT4238AEVB CAT4238 10-LED Boost Converter Evaluation Board User's Manual http://onsemi.com EVAL BOARD USER’S MANUAL Introduction CAT4237EVAL2 Board Hardware 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 5 mA 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. 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 connectors. The board schematic is shown in Figure 1. VIN LQ1 T1 C1 4.7 mF S1 GND GEN/DC GND FB SGND T2 J1 T3 R4 200 kW T4 T5 R5 10 kW SW T9 47 mH 5 1 VIN SW CAT4238 SHDN 3 4 FB GND 2 U1 C2 0.22 mF R3 1 kW T8 VOUT T7 D1 GND L1 LED T10 L2 L3 R2 100 W L4 L5 R1 6.81 W T6 L6 L7 J2 J3 J4 L8 L9 L10 Figure 1. CAT4238AEVB Board Schematic © Semiconductor Components Industries, LLC, 2011 September, 2011 − Rev. 3 1 Publication Order Number: EVBUM2019/D CAT4238AEVB 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 external 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. The board is powered from an external voltage applied to the VIN (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 Figure 2. CAT4238AEVB Board Table 1. CAT4238AGEVB BOARD LIST OF COMPONENTS Name Manufacturer U1 ON Semiconductor C1 Taiyo Yuden (or Panasonic) C2 Taiyo Yuden (or Kemet) L1 Sumida D1 Central Semi R1 Yageo R2 R3 Description Part Number Units CMOS White LED Driver, TSOT23 - 5pin CAT4238TD-G 1 Ceramic Capacitor 4.7 mF/6.3 V, X5R, Size 0805 JMK212BJ475 (or Digi-Key PCC2315CT-ND) 1 Ceramic Capacitor 0.22 mF/50 V, X5R(X7R) UMK212BJ224KG (Digi-Key 587-1287-1-ND) 1 Inductor 47 mH, Low DCR, High Current CDC5D23B-470 (or CDR6D23MN-470) 1 Schottky Diode, Low VF, 40 V, 500 mA, SOD-323 CMDSH05-4 1 SMT Resistor 1/16 W, 6.81 W, 0603 Digi-Key 311-6.81HCT-ND 1 Bourns Trimmer Pot, 1/4”, 100 W 3329W-101-ND (or equiv) 1 Yageo SMT Resistor 1/16 W, 1.0 kW, 0603 Digi-Key 311-1.0KHCT-ND 1 R4 Yageo SMT Resistor 1/16 W, 200 kW, 0603 Digi-Key 311-200KHCT-ND 1 R5 Yageo Metal Film Resistor 1/16W, 10kW (Not Soldered on Board) Digi-Key 10.0KXBK-ND L1 to L10 Nichia White LED, SMT (Optional) NSCW100 or NSCW335 10 J1 6-pin Header Connector, 0.1”, Single Strip Digi_Key S1012-06-ND (or equiv) 1 J2 to J4 2-pin Header Connector, 0.1”, Single Strip (optional) Digi_Key S1012-02-ND (or equiv) 3 Pin Receptacle (Test Points) #0149-0-15-01-30-14-04-0 (or equiv) 10 T1 to T10 Mil-Max http://onsemi.com 2 CAT4238AEVB CAT4238 EVALUATION • Monitor the voltage on FB (T5), VOUT (T7), and SW 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 the CAT4238 white LED driver: (T9) • 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, VFB (DC, 500 mV/div) for VIN = 3.6 V, ILED = 20 mA, 10 LEDs in series connected to the CAT4238 output. 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 < VIN < 5 V) between VIN (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 VIN pad to measure the shutdown current: ISD