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TL594: OUTPUT CTRL,

Kengo.Y
Guru 11255 points
Part Number: TL594

Hi team,

What is the setting when the OUTPUT CTRL pin(13pin) is open?

And then, the REF voltage is 5.6V only one device, what kind of trouble do you think?


Sincerely.
Kengo.

  • 0
    TI__Guru 74115 points

    Hi,

    If Pin 13 is open, the device control is not certain - Pin 13 has to tie to ground or to Vref based on Table 1 Function Table.

    Please add 1k ohm resistor from VREF should to ground when you measure its voltage.

  • 0 in reply to Hong Huang
    Guru 11255 points

    Hi Hong,

    Thank you for your reply.

    Do you have a threshold or hysteresis for OUTPUT CTRL(13pin)?

    About Vref,
    How about do you think why a voltage other than 5V is output?
    If any of the pins break down or become open, will this phenomenon occur?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    The datasheet is asking to tie Pin 13 either to GND or REF. So there is no specs for threshold. Please just follow the datasheet to tie this pin to GND or REF.

    REF pin voltage is measured with 1k ohm resistor and also shows the load regulation. So if < 1mA, or open, the REF load regulation is not within the datasheet. So make sure load REF with min load requirement.

    If any of the pins break down or become open, then need to specify that pin, as not any pin has a same loading like REF.

  • 0 in reply to Hong Huang
    Guru 11255 points

    Hi Hong.

    Thank you for your help.

    Could you give me advice about Vref voltage?
    My customer measured Vref voltage that was 5.6V.
    The current is flowing over 1mA.
    What kind of anomalies are possible?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    Hi,

    Based on datasheet, Vref should be in 4.95V to 5.05V on VCC = 15V when Vref pin Io = 1mA. If your test shows Vref not within the datasheet on the same operation condition, it is likely the IC on your circuit is somehow damaged or with some defects from possible damages. You can replace with a new unit to retry.

    If IC not within specs, then you may contact your local TI sales, and ask to start failure analysis to see what possible damages or defects to be and help you to eliminate possible causes in your circuit.

  • 0 in reply to Hong Huang
    Guru 11255 points

    Hi Hong,

    Thank you so much for your quick reply.

    Yes, this device is suspected of chlorine corrosion.

    Will the Vref increase if the resistance was increased by chlorine corrosion?
    Or does the Vref change if any of the pins are corroded by chlorine?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    Hi,

    The suspect sample needs to go through FA to find why its operation is outside of the specs.

  • 0 in reply to Hong Huang
    Guru 11255 points

    Hong,

    I want to know more detail about other problems when it breaks.
    I want  to verify the operation abnormality in the customer's circuit.



  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    How to move on is your decision.

    The IC operation not within datasheet needs to go through TI FA to help identify where damage or defects were from so to find ways to eliminate. 

  • 0 in reply to Hong Huang
    Guru 11255 points

    Hong,

    Thank you.
    I understood.

    Do you have a graph of changes in VREF voltage when it is 1mA or more?
    And,is there the MIN/MAX on-time or off-time regulation for output?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    Io from 1mA to 10mA Vref regulation is within 35mV so very small compared to 5V. If Io > 10mA, Vref is shutdown to zero. These are all in the datasheet. The Vref is in analog and no min/max on or off time. If you see on and off, it is likely you triggered short circuit, and you need limit your current in between 1mA and 10mA.

  • 0 in reply to Hong Huang
    Guru 11255 points

    Thank you for your reply.

    I understood of Vref.
    When Vref=0V, is Io 10mA~50mA ?


    I'm sorry that my explanation is bad.
    I will ask you another word of the same question.

    is there the MIN/MAX on-time or off-time regulation for C1pin(8pin)or C2pin(11pin)?

    Sincerely.
    Kengo.


  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    When Vref = 0, its output current can be between 10mA and 50mA.

    C1 and C2 pins max duty are based on Table 1, depends on where OUTPUT CTRL pin to connect. If connect to Vref, then C1 and C2 each max duty 45%, If connect to GND, then C1 or C2 max duty 90%.

    C1 or C2 min duty is based on Section 6.6.  

  • 0 in reply to Hong Huang
    Guru 11255 points

    Thank you for your reply.

    The output CTRLpin is connected to GND, so C1 and C2 max duty is 90% on your comment.
    Is my understanding correct that 90% is on(VCC/pull up) and 10% is off(GND/E1orE2)?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    90% means the bipolar transistor of C1-E1 and C2-E2 turn on time ratio. Please refer to datasheet page 8 and 9.  

  • 0 in reply to Hong Huang
    Guru 11255 points

    Thank you for your reply.
    I understood clearly the DUTY.

    Is it possible that the duty will remain constant if it is broken or something failure?

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Guru 74115 points

    You can try a new unit to check. But if its duty keeps constant and not follow the input, then it looks something wrong. You need to check to find out. Anything is possible but you have to check to find out if the IC is damaged or your other circuit has something wrong.