PTN78000W: Output voltage tolerance

Hello Carlo,

The output voltage range for the PTN78000W is 2.5V to 12.6V and is provided in the datasheet page 10.

In order to calculate the worst case output voltage range for Rset resistors other than 1%, equation 1 (also page 10 of the datasheet) can be solved for Vout to give you this range.

Does this answer your question?

Please expect delayed response time due to the Thanksgiving holiday, I'll get back to you early next week.

Regards,

Harrison Overturf

Harrison,

Page 3 of the datasheet indicates the set-point voltage tolerance at Ta=25°C is ±2% and an additional ±0.5% over a -40...85°C range for a worst case output voltage variation of ±3% - when the setpoint resistor is a 1%, 100ppm/°C part.

What is the worst case output voltage variation over a 10...50°C range when the setpoint resistor is a 20kΩ, 0.1%, 25ppm/°C part?

What is the worst case output voltage variation over a 10...50°C range when the setpoint resistor is a paralleled set of a 100kΩ, 0.1%, 25ppm/°C part and a 301kΩ, 1.0%, 100ppm/°C part?

For these and other future applications I was hoping to obtain the tolerance and temperature coefficients of the constants in equation (1) on page 10 so I could do the math myself.

It will be sufficient if you can answer my questions above,
Jeff

Hi Jeff,

Let me check with the team internally to see if we have more data on the temperature variation for the range you've specified above.

Regards,

Harrison Overturf

Hi Jeff,

As you mentioned, the ±2% tolerance and ±3% variation numbers include a 1% Rset resistor. Placing a 0.1% Rset resistor will improve the tolerance, but not a straight 0.9% improvement. The tolerance is made up by the internal tolerance of the reference voltage, other internal circuitry and the Rset tolerance. 

The temperature variation is not detailed enough to give you the variation by °C. It may be almost linear from -40°C to +85°C, but I do not have that data for this device to be sure.

I would have to do some digging to see if I can find some detailed validation data on this device and what went into the tolerances. 

If you send me an email directly at jarrigo@ti.com to see if I could come up with some of this old data and internal tolerances.

Thanks, Jason