How do I drive a MOSFET H-bridge with ADuM3220s?
Two ADuM3220 dual isolated gate drivers can be used to isolate an H-bridge. The high-side switches need to be PMOS devices. One device drives the low-side switches and the other drives the high-side switches. The low-side ADuM3220 is ground referenced to the isolated ground. The high-side ADuM3220’s VDD2 is connected to the bridge voltage. Its GND2 supply needs to be a gate voltage lower than the bridge voltage. A Zener diode from VDD2 to GND2 is a possible implementation. The Zener should be biased to at least the ADuM3220’s maximum IDD2 with a resistor from the high-side ADuM3220’s GND2 to the isolated ground. Refer to the link below for a more detailed explanation and schematics.
In telecom power application, the input voltage can up to 75V and the power rate can be hundrends of watts. PMOS has the larger Rdson and lower Vds compared with NMOS, so the NMOS is alway adopted for both low side and high side. Is there any isolation & driver solution about this?
Hi Irving - You can use three ADuM3220's to drive an NMOS H-bridge, as shown in the attached schematic. One of the ADuM3220s drives the low-side switches; the other two drive the high-side switches. The propagation delays of the ADuM3220s will be within 12 ns of each other (max prop delay skew). Another option is using two ADuM7234s or ADuM1234s, as show in Figure 1 of the Inside iCoupler Technology article in my post above.
Thanks,Nikolas. it seems this could work. some minimor questions:
1. In you schematic, why the VDD2 of ADuM3220 placed in the middle is connected to the Vbridge?
2. Is it necessary to place a 10uF cap for the VDD2 of ADuM3220? for the half bridge driver (i.e. UCC27201), it has only a cap (0.1uF or 1uF) and has a internal diode.
3. Has this solution been already verified on the power board?
4. the current proposal for isolation and half bridge driver are 1*ADuM3210 + 2*HB driver(i.e. UCC27201) for two control signals or 2*ADuM3210 + 2*HB driver for four control signals. What are the advantage of ADuM3220 solution compared with current solution? Cost, size or performance?
I got it. I believe that the ADuM3220 may have better performance. furthermore, if there are some data available, it will be better. However, the customers think the current solution (that is half bridge drivers + ADuM3210) can meet the performance requirement. The urgent things for them are to reduce the cost and save the board space.
Compared with the half bridge driver solution, about the PCB space, both solution may have the same space----please note the half bridge drivers can be 4*4mm package. So, I think if we can have the isolation half bridge driver with smaller package to save the PCB space (the ADuM7234 is too big, needs external diode and low operation temperature), it will be very competitive especially for some module power with strict size limit.
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