How to connect the biasing network to start-up a SEPIC in constant output voltage configuration with TLD509xEP

[Sharit_S]

The biasing network can be realized with a signal diode and a limiting resistor from IVCC to FBH pin.

  

With this solution the DC-DC performs as follows:

1. the soft-start routine triggers at power-up (FBH and FBL are kept above the short to ground detection).
2. When the soft-start elapses, the regulator keeps the control.

If the biasing network is connected to FBL pin the device performs the following sequence:

1. the soft-start routine triggers at power-up (FBH and FBL are kept above the short to ground detection).
2. An open load detection (i.e. the reverse current is detected as open load) can be triggered:
   • if the open load fault triggers, the SWO gate driver is disabled, the voltage on COMP pin is frozen and a fault is reported.
   • If the open load fault doesn't trigger, the regulator keeps the control.
3. If a power-up sequence is applied before Ccomp discharging the device is able to exit from the fault condition.

For more information, please check the datasheets at: https://www.infineon.com/cms/en/product/power/lighting-ics/litix-automotive-led-driver-ic/litix-powe...