DCP010505B: DCP010505B start up Current

Lei:

Request  your  complete schematic for the DCP010505BP including Vin input and output  capacitors type and capacitance value. location of input capacitors.

1A.Is the DCP010505 Sync. On/off pin, pin14 used to control the on-off function is it open/ no connection>

2. t what is the 5V input power source DCP010505BP, current rating and inrush current rating?

2a. When the initial input power is applied does the output voltage t is possible the  DCP010505 input inrush current is  loading down its input 5V power source.  

2b.   Place Scope probe on  the DCP010505BP input power source  What is the DCP010505BP Vin 5V input data characteristics  during power up mode?

2c.  Is the  5Vin voltage dropping below 4V during initial power up.

Tom

1.no connection

2.the U19 Lm1117-5V  is 1A output for DCP010505BP (2 DCP+200ma U20 LDO LM1117-3.3). input current for DCP is about 400ma.

3.Is the  5Vin voltage dropping below 4V during initial power up. Yes .it will below 3V somtimes.

Hi Lei:

anks for the schematic of the DCP010505,

 Based upon your data comment It appears there  are (2) DCP01050 on the 5V input power source(M1171-5V) including LM1171-3V3

Based upon  your data comment , It appears there  are (2) DCP01050 on the 5V input power source(LM1171-5V) including LM1171-3V3out voltage .

1. Regarding your C172 0.1µF(104 value)( change to 2.2µF and located very close to the DCP010505BP.

A,. DCP010505  series required minimum input ceramic capacitance  is 2.2µF . 2.2µF ceramic capacitor  is be located very close to and between input Pin1 ( Vin(+) and pin 2( Vin(-)

Input inrush current during startup period can over load input 5V power LM1171-5V) drooping the input voltage to below 4V.

See below  for spec.DCP010505 details on inrush current

2. There is another direct replacement converter , 1W, DCPA10505P available with reduced soft start-up in-rush current. Same package type and same pins functionality It is a direct drop in replacement for the DCP010505BP.

Tom