Other Parts Discussed in Thread: AM3359, TPS51200, TPS65217
I am helping a colleague bring up a board that has an AM3359 and is powered by LDO2 of a TPS65217D. LDO2 has an output voltage of 3.3V 400mA. The behavior seen indicates that LDO4 may be overloaded. The big question is: Is it being overloaded by design or not? Taking off components has yielded mixed results, as the board is easily damaged, and the TPS65217D doesn't come up at all.
The load on LDO2 of teh TPS65217 includes a TPS51200, the AM3359 VDDSH{1:6}, and VDD3AP3_USB{0:1}
The DDR3 memory is a a single X16 MT41K256M16TW-107:P, that runs at 1.35V and 933MHz. I was very surprised to see that there is a TPS51200 VTT regulator on the board and it is connected to 49.9 Ohm resistors that pull up the DDR3 address, clock, bank address and control lines (26 lines total). He told me that this is a recommendation from TI and Micron. I see an application note from Micron that this is what is known as an address and control line termination to VTT (page 15,16,17 of Micron TN-41-13).
How would I calculate the worst case current drawn by the TPS51200. Is the dropout voltage = (3.3 - 0.65)? What would the current for each termination resistor be? What is the worst case current draw on the VDDSH rails?
While I have your attention: I was curious as to if the bypass capacitors are something to worry about too. The formula I've always used is power=CVF. Where C is capacitance, V is voltage and F is frequency in Hz.
Thank you very much for your help.
