QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 835 LTC4441, MOSFET DRIVER LTC4441 DESCRIPTION Demonstration circuit DC835 is a MOSFET driver circuit that is designed to facilitate adding a MOSFET driver to an existing design. Demonstration circuit DC835 can be easily modified to generate different gate drive output voltages by changing the voltage divider of the internal LDO regulator. Demonstration circuit DC835 is small and allows the MOSFET driver LTC4441 to be added to an existing design in order to evaluate the performance. The board has a ground strip along one side that can be directly soldered to source pins of an SO-8 or similar MOSFET. This assures the MOSFET driver will be most effective due to low connection inductance between it’s output and MOSFET gate pin. The DC835 has a small circuit footprint. It is a high performance and cost effective solution for driving big MOSFETs in Telecom, Automotive and Industrial applications. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. QUICK START PROCEDURE Demonstration circuit DC835 is easy to set up to evaluate the performance of the LTC4441. For proper measurement equipment setup refer to Figure 1 and follow the procedure below: NOTE: When measuring the input or output voltage waveforms, care must be taken to minimize the length of the oscilloscope probe ground lead. Measure the input or output voltage waveforms by connecting the probe tip directly across the PWM INPUT or G1 output and GND terminals as shown in Figure 2. 1. With power off, connect the input power supply to Vin and GND. 2. Turn the input power source on and slowly increase the input voltage. Be careful not to exceed 24V. Higher input voltage will cause higher power dissipation in the LTC4441 LDO regulator. If very big MOSFETs are used and switching frequency is high NOTE: the power dissipation may overheat the part. Please consult the LTC4441 data sheet for details. 3. Set the Pulse Generator to 300kHz and turn the pulse output ON. 4. Check for the proper output voltage of 6V and waveforms as shown in Figure 3. PROGRAMMING GATE OUTPUT VOLTAGE Changing resistor R8 can program the output voltage at the OUT pin of the LTC4441. Do not change the value of resistor R2. The 330kohm value is required for stability of the internal LDO regulator. For more information, please refer to the LTC4441 data sheet. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 835 LTC4441, MOSFET DRIVER BEWARE OF MOSFET DRIVER DELAYS MOSFET driver delays, which are on the order of 30ns, need careful consideration. Some PWM controllers have built in leading edge blanking that prevents misstriggering of the current comparator due to leading edge current spikes. If this blanking period is too short it may not cover the additional delay caused by the MOSFET driver. The LTC4441 has a built in programmable blank- ing circuit that may be used to circumvent the shortcomings of other PWM circuit’s leading edge blanking. Please refer to the LTC4441 data sheet for more details. Demo Circuit DC835 has an input filter (R6 and C3) that is used to prevent ringing on the PWM INPUT line from causing false pulses at the output. This RC filter also adds to the delay and needs to be taken into account. The RC filter can be removed if the PWM input line is laid out correctly and is relatively short. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 835 LTC4441, MOSFET DRIVER Figure 1. Proper Measurement Equipment Setup 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 835 LTC4441, MOSFET DRIVER GND VIN Figure 2. Measuring Input or Output Waveforms Figure 3. Input and Output Waveforms with 10nF load capacitor 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 835 LTC4441, MOSFET DRIVER 5 Bill Of Material Demo Circuit 835A Linear Technology Corporation LTC4441EMSE 1/18/2006 Item Qty Reference 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 1 1 0 1 1 1 3 1 1 1 5 1 1 1 Part Description Manufacture / Part # C1 Cap., X7R 0.1uF 25V 10% AVX 08053C104KAT2A C2 Cap., X5R 10uF 10V 10% TDK C3216X5R1A106K C3 Cap., X7R 100pF 25V 10% AVX 06033C101KAT2A Q1 (Opt) R1 Res., Chip 10K 0.1W 5% AAC CR16-103JM R2 Res., Chip 330K 0.1W 5% AAC CR16-334JM R3 Res., Chip 49.9K 0.06W 1% VISHAY CRCW060349.9K1% R4,R5,R9 Res., Chip 2.2 0.1W 5% AAC CR10-2R2JM R6 Res., Chip 10 OHM 0.1W 5% AAC CR16-100JM R7 Res., Chip 12.4K 0.1W 1% AAC CR16-1242FM R8 Res., Chip 84.5K 0.06W 1% Pansonic ERJ3EKF8452V Mill Max 2309-1 TP1,TP2,TP3,TP4,TP Testpoint, Turret U1 I.C., MOSFET Driver Linear Technology Corp. LTC4441EMSE FAB, PRINTED CIRCUIT BOADEMO CIRCUIT #835A STENCIL, 20X20 STENCIL 835A, 20X20 Page 1 - of - 1 Bill Of Material Demo Circuit 835A Linear Technology Corporation LTC4441EMSE 1/18/2006 REQUIRED CIRCUIT COMPONENTS: 1 2 3 4 5 6 7 8 1 1 1 1 3 1 1 1 C2 R1 R2 R3 R4,R5,R9 R7 R8 U1 Cap., X5R 10uF 10V 10% Res., Chip 10K 0.1W 5% Res., Chip 330K 0.1W 5% Res., Chip 49.9K 0.06W 1% Res., Chip 2.2 0.1W 5% Res., Chip 12.4K 0.1W 1% Res., Chip 84.5K 0.06W 1% I.C., MOSFET Driver TDK C3216X5R1A106K AAC CR16-103JM AAC CR16-334JM VISHAY CRCW060349.9K1% AAC CR10-2R2JM AAC CR16-1242FM Pansonic ERJ3EKF8452V Linear Technology Corp. LTC4441EMSE ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS: 1 2 1 C3 1 R6 Cap., X7R 100pF 25V 10% AVX 06033C101KAT2A Res., Chip 10 OHM 0.1W 5% AAC CR16-100JM