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# LMV321: Check the RθJc parameter and calculate the Tc of LM321 application

Part Number: LMV321

Hi Sir,

I want to calculate the Tc of LM321 by Tc=Tj - (RθJc x Pd ), but I can't find the RθJc on the datasheet.

Could you help to provide the information for us?

Otherwise, could we use Vdd * IS (Supply Current) to calculate the Pd?

• Hi Teresa,
Which package do you need the RθJc information for? Please let me know.

Best Regards,
Bala Ravi
• In reply to Bala Ravi:

Hi Bala,

Update the LMV321 Thermal Information.

I need the DBV 5PIN package. Otherwise, could we use Vcc(Supply voltage) * IS (Supply Current) to calculate the Pd?

• In reply to Teresa Chiu:

Hi Teresa,
Thanks for that information. I've submitted your thermal data request. Please allow up to 3 business days to process your request. Thermal information is dependent on package type, die size and other factors. So I am not sure how accurate you can get with the equation.

Best Regards,
Bala Ravi
• In reply to Bala Ravi:

Teresa,

Tc=Tj - (RθJc x Pd ) formula will be correct only if all the heat in the device leaves via the case top. It will not in a normal soldered to a PCB application.

The formula you need is Tc=Tj - (Psi JT x Pd ) . The model will have Psi JT value.

Power dissipation is complicated. It is the sum all the below.
Pd= VCC * ICC (no load) , see data sheet.
For each output sourcing current, Pd = (VCC - VOUT) * IOUT
For each sinking sourcing current, Pd = VOUT * IOUT

Regards,
Ronald Michallick
Linear Applications

TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

• In reply to Bala Ravi:

Hi Bala,

Thanks for your help here. Is it possible to have the Psi JT value?

• In reply to Ron Michallick:

Hi Ron,

• In reply to Teresa Chiu:

Hi Teresa,
There has been a high volume of thermal data requests. Please allow couple more days to process your request. I will get back to you with RθJc and Psi JT values.

Best Regards,
Bala Ravi
• In reply to Bala Ravi:

Teresa,

LMV321IDBV
Theta JC, top 139.8 C/W
Theta JB 80.9 C/W
Psi JT 52.8 C/W
Psi JB 80.5 C/W

Regards,
Ronald Michallick
Linear Applications

TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

• In reply to Ron Michallick:

Hi Ron and Bala,

Is there any RθJC(bot) data?

• In reply to Teresa Chiu:

Teresa,

Theta JB 80.9 C/W is RθJC(bot)

Regards,
Ronald Michallick
Linear Applications

TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).