touchgfx led backlight control

[Kyrpav]

I have bought a riverdi display RVT50HQTNWC00, i want to know if at the backlight pins that the typical is 12volts i can connect a 12vdc power adapter for test or i need to use a led driver like TPS61169.

[RhSilicon]

Vf: 12Vdc +/-5%

This is a module, it should already have all the regulators and limiters incorporated.

https://download.riverdi.com/RVT50HQTNWC00/DS_RVT50HQTNWC00_Rev.1.1.pdf

Image source: https://riverdi.com/product/5-inch-lcd-display-capacitive-touch-panel-optical-bonding-uxtouch-stm32u5-rvt50hqsnwc00-b

[Peter BENSCH]

No, although it is a display module, it only contains pure LEDs without current limitation. However, since LEDs are (usually) operated with constant current, a power source must be connected. In the simplest case, this could be a power supply unit with a series resistor, which is designed accordingly, but which, depending on the voltage difference at 140mA, generates a lot of power loss.

You can also use an LED driver that can generate the required 140mA current at a flux voltage of approx. 12V from the voltage you want to provide for the backlight. This can be done with many topologies, the choice of which depends on the input voltage:

• >12V: Buck regulator
• lower and higher 12V: Buck-Boost regulator
• <12V: Boost regulator

The regulator in Riverdi's application note is a boost regulator, but you can of course use a suitable LED driver as an alternative.

Hope that helps?

Regards
/Peter

[RhSilicon]

---

No, although it is a display module, it only contains pure LEDs without current limitation

---

:see_no_evil_monkey:

It would be interesting to make this very explicit if it is not.

[Peter BENSCH]

Well, you can actually always see in the circuit of the display module how the LEDs are connected.

Assumption: since the module manufacturer does not know which voltage is to be used to operate the backlight, the necessary current regulation is usually expected externally. If a boost controller were permanently installed, this would limit the usable voltage range.

[RhSilicon]

I'm not sure this is very clear, as it is announced as Power Supply: 6V-48V.

Interesting that these recommended IC drivers are for low V. input:

• DIO5661: Input Range: 2.7V~5.5V
• TPS61169: Input Range: 2.7V~5.5V

Even HD44780 LCD are coming with built-in limiters. At $160, at least the driver could have been included :money_with_wings:

[Peter BENSCH]

@RhSilicon Uhm… you accidentally mixed up:

• RVT50HQTNWC00 (pure display)
• RVT50HQSNWC00 (complete module)

Yeah, a single letter (T vs S) and it's a completely different device. Display manufacturers tick a little differently than semiconductor manufacturers...

[RhSilicon]

That's really it, the letter T in the middle of the code. Value of $66 is more acceptable (a little expensive decorative cover glass, compared to other similar model, $22).

[Kyrpav]

almost true ,but if you place in buydisplay shiping, custom clearance the cost is around the same while this can be bought from mouser without custom clearance and free shipping. Also riverdi has example in touchgfx cause of the embedded products which makes easier to convince customer to buy it.