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How controll TPS40170 from MCU?

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Jadeit

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TPS40170 is 4.5 V to 60 V Synchronous PWM Buck Controller with 100-600kHzz switching frequency and 0,6V FB.
TPS.png

Simply put, feedback is voltage divider or in variable version potentiometer.
I need to control the output voltage from the processor and hold a simple method how?

Maybe over voltage, MCU have 12bit DAC .
You are advising?
 

Calculate voltage divider for highest output voltage and add DAC output to Vfb to reduce the setpoint.
 

Jadeit said:
TPS40170 is 4.5 V to 60 V Synchronous PWM Buck Controller with 100-600kHzz switching frequency and 0,6V FB.
View attachment 140839

Simply put, feedback is voltage divider or in variable version potentiometer.
I need to control the output voltage from the processor and hold a simple method how?

Maybe over voltage, MCU have 12bit DAC .
You are advising?
Click to expand...
You can use a ADC/DAC pair for surveillance of the output voltage level.While ADC is observing the Vout, uC and DAC give the necessary correction and pull up/down the regulator output .
A good calibration will be needed..
 

Hi,

You also may use an EEPOT / digital pot.
They can be controlled with I2C, SPI or Up/Down. Volatile or not.

Klaus
 

Thank you for the reaction
> DAC output to Vfb to reduce the setpoint.
It also occurred to me. I'm a bit afraid of the influence on the feedback loop properties.

>You can use a ADC/DAC
Do you mean fully digital feedback?
I thing for 400kHz PWn would be needed highd speed ADC, DAC and a very fast processor that could do nothing but drive the ps.

>You also may use an EEPOT
Maybe with AD5293 1024 bit max 33V diogital pot. , but this need 33V on supply AD5293
 

Hi:

How to use a DAC:

V_out = 4.5V .... 60.0V
R_U is connected to feedback node and output voltage
R_G is connected to feedback node and GND
R_D is connected to feedback node and DAC output
Let's assume R_U = 100k, DAC_Vout = 0.0V ... 3.0V. (0V gives 60V out, 3.0V = 4.5V out)

R_D = R_U x DAC_range / Vout_range = 100k x 3.0V / 55.5V = 5.40k
Let's focus on 60V output = 3.0V at DAC.
I_R_U = V / R = (60.0V - 0.6V) / 100k = 0.540mA
I_R_D = V / R = 0.6V / 5.4k = 0.111mA
I_R_G = I_R_U - I_R_D = 0.540mA - 0.111mA = 0.429mA
R_G = V / I = 0.6V / 0.429mA = 1.399k

Klaus
 

Jadeit said:
>You can use a ADC/DAC
Do you mean fully digital feedback?
I thing for 400kHz PWn would be needed highd speed ADC, DAC and a very fast processor that could do nothing but drive the ps.
Click to expand...
There is no relationship between switching frequency ADC/DAC speed because the output is DC. ADC will measure the output voltage then send the uC, DAC will take this information from uC and apply the analog voltage to PWM controller as a feedback.
 

> DAC output to Vfb to reduce the setpoint.
It also occurred to me. I'm a bit afraid of the influence on the feedback loop properties.
Click to expand...
Advantage of this solution in contrast to potentiometer is a constant loop gain.
 

Is possible use this solution with DAC, her calculated for 0-25V driving with DAX 0-3,3Vand Feedback voltage 800mV

DAC.png
 

Hi,

It´s like recommended in post#6.

But now you use different values.
I don´t want to re calculate the values. But I´ve given the formulas in post#6, so you can calculate it yourself.

I wonder why
* now your V_FB = 0.8 and not 0.6V anymore.
* now you want 0..25V and before you talked about 4.5...60V
* what´s the use of the OPAMP. Isn´t it a voltage output DAC?

Klaus
 

I solve two sources with two IC and I used an example of a smaller source from LM54145. This have 0,8V FB etc.
For driving, I think any STM32F3 this have voltage output DAC ,and internal buffer to, but internal DAC buffer worsk only in voltage 0,2 - Vdd-0,2V therefore I prefer to use external buffers
 

Hi

but internal DAC buffer worsk only in voltage 0,2 - Vdd-0,2V therefore I prefer to use external buffers
Click to expand...
I don´t know how many of these things you want to sell... but you may add an external OPAMP for every piece you sell, or once you just add a line of code.
--> there is no need to run close to the supply rails.

Klaus
 

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