I am not getting any voltage on the output side (on the VDDB pin (pin 16)) but I can see the 450KHz pulses on pins 1 and 2 (TD1 and TD2). I can also see pulses on the output of the transformer. On pin 11 (VLDO), I see what look like decaying pulses at about 7-volt average value. What can cause this?
Answer:
Insufficient, or no, capacitance at VDDB can cause this. The datasheet recommends placing 0.1uF and 1uF on VDDB, VLDO, and VDDA pin. As a first step, please follow the guidelines. The capacitor on VDDB pin is particularly important for functionality because it is connected to the output of the LDO. In one customer's case, adding the output capacitor on VDDB pin solved the problem.