[SI-LIST] Re: Regarding Output Voltage Rise time of linear Regulators.

Hi Vivek-

Our power supply group typically models both the micro and macro time
behavior of our power systems using a  simulation tool - I think their
preferred tool is SABER.  

They can model the entire power system, including performance of the
regulator itself (be it a linear or switching regulator), the
distribution network, the load, and predict both micro-time performance
(such as ripple and switching noise) and macro-time behavior such as
regulation with step changes in the load.


Steve 

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Vivekkumar M-TLS,Chennai
Sent: Friday, February 27, 2009 3:57 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Regarding Output Voltage Rise time of linear
Regulators.
Importance: High

Dear All,
 
We need to find the output Voltage regulation time of linear regulators.
Generaly when using LDO's(Linear Dropout Regulators) the Output Voltage
regulation time is given by the manufacturer himself. But in the
scenario when data is not avaliable in the spec, please can any one
confim if the following method is acceptable:
 
(Input Voltage - Output Voltage)/Load Current =  Series pass resistance
Value.
 
Let this resistance value be Rs.
 
We will have adjustable resistors which provides a feedback of the
output voltage. Let them be Ra,Rb.
 
Hence using Thevenin's theorem,
 
The effective resistance would be Rs + (Ra II Rb) = Reff.
 
The Effective output capacitance will be the total capacitance added at
the LDO output. = Cout.
 
Hence the Regulation time ( Load changing from 10% to 90%) = t
5*Reff*Cout.
 
 
Requesting everyone to give their comments on this.Your immediate
response will be sincerely appreciated.
 
Regards
Vivek
 
 


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