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Original question:

UC1845A-SP: Error Amplifier

UC1845A-SP: Sink/Source Current OUT pin

Rolf Lerch
Prodigy 90 points

Part Number: UC1845A-SP

Tool/software:

Dear Support

What is the maximal peak current at the OUT pin? Specified is 200[mA] RMS but Figure 1. goes up to 500 [mA].

I saw several designs (e.g. TIDA-070002) where a 10 [Ohm] gate resistor is used, what would implies a current of about 18V/15Ohm = 1.2 [A]. 

Question:

- How did you design the gate Resistor? I used to design the gate resistor in a way that charging/discharging current must be lower than the peak current allowed for the driver IC’s output stage to guarantee the safe operation

- What is the effective peak current (sink/source)? 

- How did you calculate the turn on / turn of time of the switching device?

- Does a low gate resistor e.g. 10 [Ohm] harm or even damage the OUT pin?

- A output energy of 5 [uJ] is specified. Is this the (stored) energy inside the device or the maximal energy delivered to the switch? 

Best Regards

Rolf

  • +1
    TI__Mastermind 31515 points

    Hey Rolf,

    That is a perfectly reasonable way of figuring out the gate resistor. Remember gate resistance of the package of the FET can also be taken into account. SUM80090E-GE3 has a 1.5-5 Ohm gate resistance.

    The max rating of the part is in table 7.1 as +/-1 A.

    The Rise/Fall times of the part is the controller bring up and down a 1 nF load on the pins with a 15 V Vcc.

    Violating our maximum ratings of our parts can damage the device.

    It is the energy delivered to the switch gate.

    Thanks,
    Daniel