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I'm an intern at Philips Technologies in Aachen, Germany.
I'm currently troubleshooting a PCB built by a colleague of mine. He has used 8 DCR010505U. According to this thread http://e2e.ti.com/support/power_management/powermodules/f/501/t/163829.aspx , the DC-DC converters can draw up to 750mA at startup. Could someone comment on that? If this is the case, then that means I need to ensure that at least 6A are supplied at startup, which would mean I will need to replace the supplying 1A switching regulator (TL2575). This could explain, why so far the output has always been 0.
My colleague seems to have done a mistake while connecting the pins. He connected the SYNC pins together and at the end with the 5V supply voltage. How critical is this? According to the datasheet, it is only required to connect the SYNC pins together.
Any help will be appreciated.
The sync. pins must never be directly connected to any bus or 5V. The unit will become extremely hot and can possibly overstress the internal components. The sync. pins can be connected to each other if there is more than1 DCR.
the maximum input inrush current can be as high as 750mA. The slope of the input power source dv/dt and its current rating will affect the inrush current .
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In reply to Tom Guerin:
Thanks for the fast response. I'm testing 1 DCR010505U to check it is damaged. The SYNC pin is floating, input voltage is 5V, input capacitor 2.2uF and output capacitor 1uF. However the output voltage is too low about 200mV. A TL2575 (max. 1A) is supplying the component. Any ideas?
In reply to Hamze Hachem:
Thanks for the input. I missed the 8 x DCR010505U are powered from 5 -1 Amp TL2575.
The input voltage and input power source is not capabilty of supplying the current necessary to operate the DCR series.
The formula for input current is Input current= Output power( Vout * Iout )/ ( efficiency * input voltage).
Example Input current = ( 5Vout)* 0.1Amp ( output current)/ ( 55% efficiency * 5Vin (input voltage) = 181mA input current .
8 ( number of units ) x181mA 1.45A required by the 5V TL2575 1 amp regulator.
the inrush current can be as high as 750 Ma fro each DCR010505.
You must increase the input power supply to at least 6Amps.
yes I already know that (check my first post). However, TL2575 should at least be able to supply 1 x DCR010505U, this is does not deliver the promised result (check my last post for more information). Could it be that my colleague damaged the component after connecting SYNC to the supplying voltage? Any other ideas on how to test the component further?
Thanks in advance
Yes the DCR can be damaged if there is 5V applied directly to the sync. pins.Did you measure the input voltage directly on the single DCR010505U pins 1or 2 and 27or 28?The sync. pin should not be connected to any other unit or 5Vin.
The SYNC pin is floating, power has been cutoff from the other units. relative to pin 27 (0Vin), I get the following results:
pin1 and pin 2 Vs =5V
pin27 SYNC= 5V (The unit is on)
The unit is extremely hot!
My guess is, there is something connected to the DCR, that is drawing too much current, so that the voltage is dropped since the unit delivers a power of 1W. But I may be wrong...
connected the DCR directly to the PSU. Still no output!
The no operation of the DCR010505U which originally had 5V directly connected to the sync. pin is likely to have been overstressed. the DCR01 will have to be replaced.
I disconnected the output circuit from the DCR, now the DCR delivers around 6V. I believe I was right, the output circuit is drawing too much current. Which makes me wonder, does the output current have an upper bound? The datasheet presents only a lower bound of 200mA.
The DCR010505 absolute operational maximum output current is 200mA. Any current above this limit can shutdown the converter.
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