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TLD1114-1EP: Possibility of digital dimming without MOSFET in power shift circuit

TLD1114-1EP: Possibility of digital dimming without MOSFET in power shift circuit

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TLD1114-1EP: Possibility of digital dimming without MOSFET in power shift circuit

When the TLD1114-1EP is used without the MOSFET no PWM dimming over PWMI, EN or IN_SET pin is possible. PWM operation over supply VS is possible as there the current path to the LEDs is disconnected by the switch supplying the module.

tld1114_power_shift_without_NMOS_current_path.png

The reason is that the LEDs are always connected to the Power Shift resistor without an active switching element to disconnect. Please have a look on the attached figure.

The current path (shown in green) is always closed as there is no switch to open it.

This means even if you deactivate by EN/PWMI or INSET some current is flowing depending on the power shift resistor.

The current can be estimated with IOUT ~(VS - VLED)/(Rpowershift + Rshunt), where

   - Rshunt = 750mOhm if OUTH is used

   - Rshunt = 1500mOhm if OUTL is used.

This means that the only way to turn off the LEDs is to deactivate the power supply (as done e.g. in a fog light).

In case you want to do the wiping animation you will have to use the Power shift feature WITH mosfet.

See TLD1114-1EP Powershift appnote for further details:

https://www.infineon.com/cms/en/product/power/lighting-ics/litix-automotive-led-driver-ic/litix-basi...

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