power rating required for the damping resistor in the pi prefilter circuit as described in the AN1120.

Question

Hi Team! 
 
 I have gone through the Application Note 1120 Noise source in the LDO. I need to work the circuit on the 24V battery with automotive noise protection. I have used PI prefilter to increase PSRR mentioned in the AN. The values of the components used are as follows: 
 Lf = 10uF, 
 Cf = 22uF 
 Cd = 220uF 
 Rd = 1E. 
 To select the values of the filter, I have referred to the formula mentioned in the AN. 
 My question is I am enable to identify the power rating required for the resistor Rd. 
 Kindly help me to identify the power rating of the resistor Rd or formula to recognize the current flowing through the branch. 
 
 (The circuit used is from Fig 14 of the AN1120.). 
 
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bgonzales · Accepted Answer

Hi! 
 You can refer to this article for calculating power rating of the damping resistor/snubber: 
 R-C Snubbing for the Lab (maximintegrated.com) 
 
 For example: 
 CS = damping/snubber capacitor = 220uF 
 Vpk = peak capacitor voltage, i.e. 2.5V rating of capacitor for ADP1765 
 Ft = corner frequency = ~10kHz from your example 
 Power Rating of Rd &ge; 15W 
 
 Hope this helps, 
 Bryan)

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power rating required for the damping resistor in the pi prefilter circuit as described in the AN1120.