• State
  • Locked Locked
  • Replies 8 replies
  • Subscribers 66 subscribers
  • Views 1098 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SM72295: short circuit between VDD and AGND

Johannes Urban1
Prodigy 30 points
Other Parts Discussed in Thread: SM72295, SM72442

Hello,

we are using the SM72295 as a driver for a full bridge DC/DC converter. VCC is connected to 12V and VDD is connected to 5V and bypassed with 100nF as described in some application notes and the datasheet. (BTW: There is a mistake in the datasheet, VDD is listed as "output")

it happened now two times that there was a short circuit in the chip between VDD and AGND, one time it happened without there was any voltage on the HB and HS pins and no pulses on the input pins. So even in this mode, where the driver didn't do anything VDD broke though!

SIA, SOA, SIB and SOB are pulled down GND with 10kOhm, IIN, BIN, BOUT and IOUT are pulled up to 5V also with 10kOhm, because those amplifiers are not used.

Can you give me some adive here, how can I protect the SM72295 from breaking?

Best wishes

Johannes

  • 0
    Prodigy 50 points

    I have got the same problem, but I destroyed more than two SM72295. First, I thought the problem was on current sensing circuit (I use all two amplifiers), but you have the same problem without using them. Yesterday, I noticed it breaked when I shut off the system.

    I don't understand also why it is very difficult got information and assistance about solar magic product in this, and other, forum.

    alessandro

  • 0 in reply to alessandro fici
    Prodigy 10 points

    We are also implementing MPPT solar charger using SM72442 and SM72295. We are facing the same problem. After a short period of time the AGND and Vdd pins get shorted. Please let us know if get to know the reason....

  • 0 in reply to SMIT SHAH1
    Prodigy 90 points

    Is it failing at full power ?? We are not facing this problem in our circuit. We are using this SM72295 in inverter and DC/DC module also. We are faced only bootstrap cap conking off and current sensing poor accuracy

  • 0 in reply to Srikrishnan R
    Prodigy 30 points

    Hey! As I wrote above this was s serious problem for me last summer.


    I got a workaround or at least I managed to keep the chip alive for some time, I do not know if this is the solution:

    The VDD pin has to be secured. As i see it it is only for voltage sensing so the is no big input current needed. I put a 1kOhm resistor between 5V and VDD and I put in a Z-Diode that works at low currents between VDD and GND.

    The resulting working point at the VDD pin was 4.7V then and it worked fine. At this point VDD cannot get destroyed though high input currents.


    Hint: Take a look at the application notes of the SM72295, in one of the example curcuits VDD is secured they way I described it above.


    Greetz and good luck

  • 0 in reply to Srikrishnan R
    Prodigy 15 points

    I worked out the AGND vDD short problem.......but when we give the PWM signals from sm72442 to sm72295 pins LIA,LIB,HIA,HIB sm72295 outputs dont give switching pulses(PWM) on the HOB and HOA pins. Instead it isalways 12v and keeps the mosfet on alwayzz. Why doesnt it provide switching pulses(PWM) at the outputs HOA and HOB. It does provide PWM pulses at  LOA and LOB. Plzz reply ASAP.

  • 0 in reply to Smit Shah
    Prodigy 90 points

    Hai smit,

    but i m not using sm72442 IC . I m feeding the PWM's directly to the sm72295. First check the deadband how much you are givin, if it is very low bootstrap cap may not have enough time to charge. So try increasing the dead band value or decrease the cap value

  • 0 in reply to Smit Shah
    Prodigy 10 points

    Hi,

    I have similar problem, what was the solution for AGND VDD?

    Steve

  • 0 in reply to gnyalini
    Prodigy 30 points

    Istv��n Gny��lin said:

    I have similar problem, what was the solution for AGND VDD?

    Read my post above from Apr 03 2014 01:51 AM. I posted a workaround that solved it for me.

    Greetz