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opa548 E/S pin

shivani kapadia
Prodigy 10 points
Other Parts Discussed in Thread: OPA548

Hi,

I was trying to disable this chip using the E/S pin. The voltage I measured on the E/S pin while the chip was enabled was -8.48V. It is written in the data sheet that the E/S pin has to be pulled close to -VEE+0.8V to disable it. Since my VEE = -12V , I tried pulling it close to 11.2V but it did not turn the output off. I was wondering if there was any other way to disable this chip or if I was doing something wrong.

 

Thanks,

Shivani

  • 0
    TI__Guru 64530 points

    Shivani,

    First of all, I assume you meant to say that you pulled down the E/S pin down to -11.2V and not +11.2V.  It needs to be anywhere between -12V and -11.2V to be disabled (for Vs=+/-12V) - see below.

     

    Second thing is that OPA548 is one of our older parts designed on a bipolar process which means its IQ current in shutdown mode gets typically lowered only to 6mA with E/S at -VEE (see below).  At  -VEE+0.8V the IQ current will be greater than 6mA.

     

    In the shutdown mode the output get disabled allowing multiplexing of signals with frequency lower than 20kHz.  Higher frequency signal than 20kHz will cause the leakage current to increase in shutdown devices beyond specified 6mA (see text below).

     

     

  • 0 in reply to Marek Lis
    Prodigy 30 points

    In our company we are using OPA548 for programmable power supply application purpose.We have used your Digitally-Controlled Programmable Power Supply schematics for our application refer to page number 15 of OPA548 datasheet .Whatever mentioned in that schematics ,used all IC and capacitor except resistor(used 10k and 4.12k instead of 9k,1k respectively for a gain 3.4)  .

                     We are facing problem with OPA548 IC , IC gets very much heated after connecting to the load then it goes to the thermal shutdown within  40 second for both higher current and lower current.Without load there is not much heat in the IC.We provided heat sink to the OPA548 IC ,tried with big heat sink but still same problem. Can you suggest a solution for this problem.....?