Original question:
Hi team,
What role does Q1 play in the non-isolated circuit shown in Figure 8.2 of the datasheet and on the following page?
Also, what specifications are required for Q1?
Both Vceo and Vcbo are -80V for Q1 in the schematic attached to the above thread, but is that level of breakdown voltage required?
Thanks.
Hi Sir/Madam,
Thanks for reaching out to us!
Q2 was used for the feedback control transfer function. Similar structure could be find in the below thread (FB voltage changes from 1.25 V to 1.75 V with TPS23755). V_EB of the PNP could be 0.7 V. The voltage rating of this PNP should be higher than VDD - PGND, which is up to 57 V for PoE. So you can use a 80-V rated PNP.
Please let me know if you have any further questions.
Best regards,
Diang
