DEMO MANUAL DC1902B LT4320 Ideal Diode Bridge Controller Description Demonstration circuit 1902B features the ideal diode bridge MOSFETs, a bypass ceramic capacitor, and an AC smooth- controller LT 4320 suitable for applications that require ing capacitor (C ). The DC1902B includes low R LOAD DS(ON) low to medium current AC to DC full-wave rectification N-channel MOSFETs (10m typical) to support low to or DC polarity correction and a small compact solution medium current applications. When an AC voltage source (see Table 2). is used, the onboard C (C2) capacitor allows for up LOAD to 1.5A of average output current. Add additional C LOAD The LT4320 drives four N-channel MOSFETs to perform capacitance to support higher current AC applications. A full-wave rectification functionally similar to a diode bridge unidirectional TVS (D1) is included to protect the applica- but with much lower power dissipation. This topology eases tion from brief overvoltage events up to the part rating. A thermal design, and increases usable output voltage. In footprint for bidirectional TVS (D2) is also included and is addition, an all N-channel topology has benefits over a recommended for electrically harsh conditions. P-channel topology such as a wider selection of MOSFETs, lower cost, lower R , and smaller footprint. Design files for this circuit board are available at DS(ON) DEMO MANUAL DC1902B Quick s p D 1. Connect a DC or AC power supply to VIN1 and VIN2 in 4. For an AC input, raise the output voltage of the AC power any polarity as shown in Figure 1. Make sure the output supply to the desired level. Make sure the load current voltage of the DC or AC power supply is within the input is within the current limits as shown in Table 2 with the voltage range of the DC1902B as shown in Table 2. demo board supplied C (C2). Add additional C LOAD LOAD capacitance, if higher output load current is desired. With 2. Connect a load and a voltmeter across VOUT+ to VOUT an oscilloscope in place of the output voltmeter, make as shown in Figure 1. sure the lowest point of the output voltage (droop) is 3. For a DC input, raise the output voltage of the DC power above the minimum operating voltage specified in the supply to the desired level. Check the DC1902B output LT4320 data sheet. voltage across VOUT+ to VOUT. The reading should Note: Maximum load current with an AC input should be be very close to the input voltage of the DC1902B. limited to about 3A due to MOSFET and PCB limitations. Table 2. Maximum Load Current per Input Voltage and Type of Voltage Source VOLTAGE SOURCE INPUT VOLTAGE MAXIMUM LOAD CURRENT DC 9VDC to 60VDC 3.5A AC, 60Hz 12VAC 0.7A* RMS AC, 60Hz 24VAC 1.5A* RMS *Limited by demo board supplied C2. Figure 1. DC1902B Setup dc1902bfa 2 ure roce tart