What is the function of trim in DC-DC converter

[engr_joni_ee]

Hi, I just found DC-DC converter. I am wondering about the pin called trim. What is the function of that pin in terms of controlling the output voltage ?

TEP 60-7218UIR | Traco Power

www.tracopower.com

 

[KlausST]

Hi,

* open the PDF
* do a PDF search for "trim"

and immediately get this information:
Output Voltage Adjustment –20% to+10% (By external trim resistor) See application note: www.tracopower.com/overview/tep60uir

What else do you need to know?

Klaus

 

[engr_joni_ee]

Hi, can this be done by PWM signal as trim signal to adjust the output ?

--- Updated Mar 22, 2022 ---

I also found this trim pin in thn-30-2425wi. How much I can adjust the output voltage ? The output voltage is +/- 24 V

THN 30-2425WI | Traco Power

www.tracopower.com

 

[stenzer]

Hi, can this be done by PWM signal as trim signal to adjust the output ?

I doubt that, at least not by applying the PWM directly to the trim pin. The datasheet does not give any information about the topology of the trim-pin, but usually a feedback network is adjusted with this kind of inputs (sink/source current). The "tep40uir_tep60uir_tep100uir_voltage_adjustment" document available within the application notes folder [1] mentions a resistor with a power rating of 1/8 W.

https://www.tracopower.com/int/media/14155/download?attachment

BR

 

[KlausST]

Hi, can this be done by PWM signal as trim signal to adjust the output ?

--- Updated Mar 22, 2022 ---

I also found this trim pin in thn-30-2425wi. How much I can adjust the output voltage ? The output voltage is +/- 24 V

THN 30-2425WI | Traco Power

www.tracopower.com

PWM: the datasheet talks about an external resisitor. If you do something else then the risk is on you.
I didn´t read the traco application note. Did you?

How much...? What´s wrong with the "-20% to +10% " specification? It´s rather clear.

Klaus

 

[dick_freebird]

Dc-dc feedback tends to be a divided image of the load against
an internal bandgap reference. Simplest is a bare resistor pair
outside the control chip, but some PMIC vendors will pull those
inside, to claim their BOM cost and into the chip pricing and
show a better close-in layout area.

If you have an internal divider you can bend it by parallel external
resistance. To GND is easy and lowest error-band, involving only
the on-chip resistors' tolerance and tempco, and raises the
VOUT. To lower it you need to pull against a higher voltage, which
may be the much sloppier VIN if you have no other source or don't
want to pay for one ($, area, current) on top of the on-chipff-chip
resistor mismatch statistics.

I believe you -could- use a PWM'd and filtered "5V" chop to be
your pull-to voltage. You'd have a real time adjustable scale / offset
factor then, which could deflect VOUT in either direction. But now
you have to ask yourself, "what basis will I use, to set it?" What is
there for you to use as a reference besides the reference you are
trying to bend?