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TPS7A3301 – About Input & Output , Noise reduction Capacitors

Hide
Guru 21045 points

Hi,

 

Our customer would like to use TPS7A3301 on the following conditions.

Could you please give us your advice?

And , could you please tell me your E-mail address?

I can convey the parts number of the capacitors.

 

 

[Customer conditions]

Vin = 5.5V

 

Vout = -5.0V

 

Iout = 50mA (max)

 

Cin = 1000uF+/-20% / ESR=12mohm (OS-CON)

+ 1uF +/-10% / ESR= No data (film capacitor)

 

Cout = 390uF+/-20% / ESR=14mohm (OS-CON)

+ 1uF +/-10% / ESR= No data (film capacitor)

 

Cnr = 1uF +/-10% / ESR= No data (film capacitor)

-----------------

 

[Question]

-       Is the output of TPS7A3301 stable with this condition?

-       Must we use the ceramic capacitor?

Therefore, Must we not use the OS-CON and film capacitor?

-       Do they(Cin , Cout , Cnr) have the upper limit of capacitance?

-       Do they(Cin , Cout , Cnr) have the upper limit of ESR?

 

Regards,

Kanemaru

  • 0
    TI__Guru 55940 points

    Hi Kanemaru,

    Please allow me a couple of days to look into this for you.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Guru 21045 points

    Hi, Ryan

     

    Thank you for your immediate reply.

    I’m looking forward to your reply.

     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Guru 55940 points

    Hi Kanemaru,

    A high value of capacitance is not a problem for either the supply or output.  We have simulated and tested up to 47uF with no issue.  The device is stable with ESR between 20mOhm and 50mOhm and ESL less than 1nH.

    For Cnr, there is no gain in noise performance going higher than 1uF; therefore, we recommend staying with the 1uF capacitor.

    So long as the ESR, ESL, and capacitance remain within the above requirements over the operating conditions, there is no reason that the capacitor need to be a particular chemistry.  Ceramic is recommended because of performance over temperature.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Guru 21045 points

    Hi Ryan,

     

    I’m sorry for the delay in my reply.

    Thank you for the information.

     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    Prodigy 30 points

    Hello I have a problem with the TPS7A3301EVM-061.

    In practice, I would benefit from going out to-12V.

    From the datasheet of the regulator TPS7A3301 the values ​​of the resistors R1 and R2 are, respectively,-12V Recommended for:
    R1 = 1.5 Mohm
    R2 = 162kohm

    I took smd resistors with 1% tolerance

    Just connect the input voltage of 15V linear power supply with adjustable lab I have the following voltages:

    Vin = 15V

    Vout = -14.34

    Fri = -14.92

    Vnr / ss = -12.18

    Vref = -11.66

    dropping the voltage Vin is lowered even until Vout with a voltage of Vin = -12.6 I can have -11.98.

    But not so is fine the voltage should be constant and ever-12Vout, the variation of Vin.

    Please expect a ready help.

    Thank you.

    Michael.

  • 0 in reply to michele mirenda
    TI__Guru 55940 points

    Hi Michael,

    Please confirm that your 15V input was a negative 15V in your above conditions.  If it was positive as stated above, this exceeds the absolute maximum rating for the input pin.

    Please also indicate how you are measuring Vref and Fri.  If possible, please provide scope shots as well.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 30 points

    Thank Ryan.

    I have a Vin-15V input from Lm 7915.

    Vfb,  I measure between pin 7 and GND of the controller with the multimeter measures 12.05 V
    Ven is also 15V

    Vout always 14,24 V.

  • 0 in reply to michele mirenda
    TI__Guru 55940 points

    Hi Michael,

    Please check your board for shorts.  In particular, check for shorts around the resistor divider.

    Please provide scope shots of Vin, Vout and if possible Iout.  These will help greatly in debugging.  Also, in your first post you mentioned Fri and Vref nodes.  Please indicate how you are measuring these.   

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 30 points

    hello Ryan in the resistive divider as I told you I put two resistors smd

    r1 = 1.5 Mohm 
    r2 = 162kohm 
    They are the right values ​​for 12V.

    Sorry if these questions do not is that they are very expert.

    Vin and Vout seems to me to have them written in 'last post.

    I'm sorry but sometimes I can not understand difficulties to translate.

    Vref does not coincide with Vfb?

    Quando faccio le misure non ho collegato in uscita nessun carico solo il tester per misurare l'uscita.

    Grazie ancora