Question
Are pin 3 and pin 9, pin 12 and pin 18, internally connected?
So if I power the ADN4551 with 3v3, I have to connect a 1uF capacitor between pin and gnd on both pin 3 and 9 to gnd1 and pin 12 and 9 to gnd2?
The datasheet says only pin 3 and 18
Answer
No, these are not internally connected.
Please see the attached diagram from page 36 of the datasheet:
100 nF decoupling is recommended at each Vdd1/Vdd2 pin.
Pins 3 and 18 double-up as the LDO output, so when supplying 3.3V to pins 1 and20, we recommend additional 1 uF caps at the LDO output (pins 3 and 18) as asmall reservoir cap for load spikes (actually the LDO will work reasonablywithout these, but the 1 uF caps are good practice, so we included them in therecommendations). The LDO is one of our “anycap” LDOs, so even 0402 caps forthe 1 uF caps will suffice.