Hi Team,
My customer would like to know allowable max and min cap values for Vo and VTTref.
I need to understand well datasheet description to answer their questions so let me ask some questions.
1. From the Datasheet description, I understand that the following are the allowable max and min cap value, is that correct?
2. Is this recommended cap range the same for different output voltages like Vo : 1.25V, VTTREF : 0.675 for DDR3L?
3. I didn't find the maximum cap value description of Vo in Datasheet, are there any restrictions?
[VTTREF]
Max : 0.47uF
Min : 0.1uF
Reference output. Connect to GND through 0.1-μF ceramic capacitor. If there is a REFOUT capacitors at DDR side, keep total capacitance on REFOUT pin below 0.47 μF. The REFOUT pin can not be open
Refer to "5 Pin Configuration and Functions" in datasheet
[Vo]
Max : ?
Min : 20uF(ESR should be smaller than 2m ohm)
For stable operation, the total capacitance of the VO output pin must be greater than 20 μF. Attach three, 10-μF ceramic capacitors in parallel to minimize the effect of equivalent series resistance (ESR) and equivalent series inductance (ESL). If the ESR is greater than 2 mΩ, insert an RC filter between the output and the VOSNS input to achieve loop stability. The RC filter time constant should be almost the same as or slightly lower than the time constant of the output capacitor and its ESR.
Refer to "8.2.2.3 Output Capacitor" in Datasheet
Regards,
Takashi Onawa
