JAJSNN2A October 2023 – December 2023 UCC25660
PRODUCTION DATA
The TSET pin voltage is used to set the VCR integrator time constants and the minimum switching frequency. Depending on the selected option, OCP1 threshold, Timer gain (ks), Integrator component values (RVCR, RRAMP, CVCR), maximum dead time would be set.
For this design, TSET option #4 is selected. So, for option #4, TSET pin voltage needs to be between 0.742V to 0.85V as given in table TSET Programming Options table . A 1M ohm (RTSET_upper) and a 191kΩ (RTSET_lower) are used at the TSET pin. Then the TSET pin voltage will be
Then the Equation 4 will become
where previously chosen values of RISNS, CISNS, CR, RBLKupper, RBLKlower, Integrator time constants values of TSET option #4 are used to obtain this relation.
Here for calculating Pin, 92% efficiency is considered in the following expression.
Figure 8-2 shows the FBReplica voltage with respect to the input power of the LLC.