ACAP, DCAP and RCAP of ADAS3023

Question

Hi 
 I am FAE in Japanese distributor. 
 Our customer evaluates ADAS3023. 
 ACAP, DCAP and RCAP are used 10uF and 0.1uF as shown in Datasheet. 
 AVDD,DVDD and REFIN are used 10uF and 0.1uF as shown in Datasheet. 
 After power on, the voltage of DVDD and AVDD goes from 5V to 4.3V for about 65usec when PD is released. 
 The power up sequence of ADAS3023 is strictly regulated. 
 Does the voltage down violate power up sequence ? 
 Our customer has already confirmed the voltage down was not observed in case of AVDD,DVDD and REFIN are used only 0.1uF like EVAL-ADAS3023EDZ. 
 To prevent voltage drop, should they increase capacitance of AVDD,DVDD and REFIN form 10uF to 50uF or decrease capacitance of AVDD,DVDD and REFIN from 10uF and 0.1uF to only 0.1uF? 
 Best regards 
 N.Kokubo

@skowalik · Accepted Answer

Kokubo-san, 
 The voltage drop, as it occurs at the end of the power-up sequence, does not violate the power up sequence recommendations in the datasheet. 
 As you have probably already deduced the voltage drop is caused by an inrush of current related to the charging of the 10uF capacitors associated with ACAP, DCAP, RCAP. If the performance observed with the evaluation kit was sufficient for the customers needs I would recommend going with that configuration as the outcome is known and proven across much of our laboratory evaluation to be robust. I need to think about how to appropriately reduce the impact of the charge load from the LDO outputs (*CAP) from the input perspective if the 10uF option on ACAP, DCAP and RCAP were to be used.. 
 Regards 
 Sean)

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ACAP, DCAP and RCAP of ADAS3023