SP7616 SI2343 MMBT3904 GRM21BR CA95035

Solved by TM SP7616 Dual Supply: 5V Vcc and 12V to 30V input LED Driver Designed by: Matthew Szaniawski Part Number: SP7616

Design Solution#56 Solved by TM SP7616 SP7616 Dual Supply: 5V Vcc and 12V to 30V input LED Driver Designed by: Matthew Szaniawski Part Number: SP7616 SP7616 Application Description: Using Sp7616 with 2 supply voltages one for part Vcc and one for powering the LED chain. Electrical Requirements: Vcc Voltage Input Voltage Output Current Vcc = 5V Vin = 12V to 30V 10mA to 240mA SP7616 SP7616 Schematic with voltage sequencing: Vin 12V to 30V 100K Mar 29-07 Design Solution 56 Page 1 © 2007 Sipex Corporation Circuit Description: The circuit in this design solution allows the user to use two separate voltages for driving the SP7616 SP7616 low side driver without worrying about proper sequencing. The transistor and FET circuit will enable the two source voltages in the proper sequence. The required sequencing requires Vin, pin1 of SP7616 SP7616, to be up before there is a voltage on the LED1-4 pins. Vin needs to be greater by 2V as compared to VLED 1-4 for proper startup and operation. In this situation the user can also tie the PWM pin right to the Vin pin on the SP7616 SP7616, if not used. The sequencing circuit uses a small SOT-23-3 P channel FET that is turned on by the use of transistor Q1. Q1 threshold can be set by the resistor divider R1 and R2. R3 and R4 resistor combination creates a voltage divider that prevents the Q2 FT gate to source voltage getting too large (20V rating) which could damage the FET. The circuit is designed to work with 12V to 30V input. This report includes the application schematic complete with component part numbers and figures 1-4 illustrating electrical performance of the design. Vin 25V Vin 25V Anode Voltage Anode Voltage 5Vcc 5Vcc Figure 1: Fast Ramp on 5Vcc Mar 29-07 Figure 2: Slow Ramp on 5Vcc Design Solution 56 Page 2 © 2007 Sipex Corporation Vin 21V Vin 21V Anode Voltage Anode Voltage 5Vcc 5Vcc Figure 3: Fast Ramp on 5Vcc Figure 4: Slow Ramp on 5Vcc Bill of Materials: Line Ref. Qty. Manuf. No. Des. 1 U1 1 Sipex 2 Q2 1 3 Q1 4 Layout Component Part number DFN Low side driver SP7616 SP7616 Vishay SOT-23 P channel FET SI2343 SI2343 1 Fairchild SOT-23 NPN transistor MMBT3904 MMBT3904 R1 1 Vishay 0603 22.1K ohm 1% 5 R2 1 Vishay 0603 150K ohm 1% 6 R3 3 Vishay 0603 200K ohm 1% 7 R4 2 Vishay 0603 100K ohm 1% Resistor 8 RSET1 1 Vishay 0603 46K ohm 1% Resistor 9 C1 1 Murata 0805 1.0uF Ceramic X5R 50V Size GRM21BR GRM21BR&1H10 512L For further assistance: Email: WWW Support page: Sipex Application Notes: Sipexsupport@sipex.com http://www.sipex.com/content.aspx?p=support http://www.sipex.com/applicationNotes.aspx Sipex Corporation Solved by TM Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA95035 CA95035 tel: (408) 934-7500 faX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Mar 29-07 Design Solution 56 Page 3 © 2007 Sipex Corporation