An Engineer in Wonderland – Hunt for a mosfet driver 2

Way back in November last year I was looking for a mosfet driver that would drive a top p-fet and a bottom n-fet so that I could run a half-bridge at 100% duty cycle.

Despite helpful replies from both Jeremy and Yilcan Guzelgunler, I got nowhere.

And so, heroically, gave up.

Now I am having another go, removing the 100% duty cycle requirement to make things a bit easier.

So two n-fets are now allowed on the output, as is a bootstrap circuit to power the top fet.

However, the logic end of the circuit has now only got a Li-ion cell to run from – so I am expecting to use mosfets with a low gate threshold – and the thing still has to operate from a bridge supply of between 4 and 20V.

Operating frequency will be somewhere in the 50kHz-1MHz range.

A pair of 2A mosfets inside the package as well would be icing on the cake.

Any ideas?

‘Alice’

reply below, or to alice@electronicsweekly.com

Tags: Alice, Engineer in Wonderland

Related Tech News

4 Comments

  1. 'Alice'
    September 28, 2009 13:35

    Thanks again Ian.
    I have access to a PIC, so maybe it is time to climb the learning curve on its PWM peripheral.
    Apparently, Vishay is going to put a SUD50NP04 in the post to EW towers.
    So thanks to them as well.
    Just need to find some time to do all of this now.
    ‘Alice’

  2. Ian Cash
    September 15, 2009 16:31

    I’m glad these parts look promising!
    I drove the inputs separately via a micro (a PIC running from a separate 3.3V logic supply), and allowed 250ns dead-time – speed was not the issue in my application (fixed 15kHz square-wave).
    I don’t believe there is any “shoot-through” protection circuitry built-into the TC442xA range as they are aimed at general-purpose MOSFET driving, not just bridge configurations.

  3. 'Alice'
    September 15, 2009 14:47

    Thanks Ian.
    Those two look like they will hit the spot.
    Shame the output impedance of the driver is not 0R1, as it could do the whole job on its own.
    I have requested samples.
    Did you drive the two inputs with a single waveform?
    And if so, did you get conduction overlap?

  4. Ian Cash
    September 15, 2009 10:30

    Have a look at Microchip’s TC4428A Mosfet driver. This should meet your original requirement for driving complementary N / P fets in an H-bridge, from 4.5V to 18V supply (22V max). Switching speed is 30ns (typ) and the datasheet shows operation up-to 2MHz. Since the top P-fet requires no boot-strapping, this will work down to dc (100% duty). The logic inputs have TTL thresholds, so are suitable for Li-ion. With both inputs low, both MOSFETs are off and the driver consumes 80uA typical from the rail. I used a single Vishay SUD50NP04 complementary MOSFET in a 5-lead D-PAK, which is good for 8A. Hope this helps!

Share your knowledge - Leave a comment