H-bridge with ADuM3220

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.

    http://www.analog.com/static/imported-files/tech_articles/Inside_iCoupler_Technology_Driving_an_H_Bridge.pdf

  • 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.

    Nik

  • 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?

  • Hi Irvin

    1. Good catch.  The corrected schematic is re-posted in my original reply.
    2. This depends on the load you’re driving.  For loads that need lower peak currents, you can use a smaller capacitor than 10uF. If the load is not too high, you can use 1uF caps. 
    3. We haven’t verified this solution in the lab. 
    4. The ADuM3220 solution has performance advantages over the two control signal version.  The half-bridge driver that you suggested has a maximum propagation delay of 45-50 ns.  The ADuM3210 has a maximum prop delay of 50ns.  This is a 100ns maximum prop delay vs. 60-68 (5V VDD1) or 62-72 (3.3V VDD1) for an ADuM3220.  The ADuM3220 has better drive capability than this half-bridge driver too. It has the same performance advantages over the 4 control signal version and requires less components (three SO-8s vs. four).  I attached a four-control signal version.

    Nik