T
treez
Guest
Hi
We are using the DCM36623T50M53C2T00 DCDC module from Vicor.
Page 21 of its datasheet says that the downstream part of the input filter should be 20uF of ceramic capacitance..
..We agree that ceramic SMD capacitance is needed because otherwise there may be instability when the load has heavy transient behaviour. So the filter will need to comprise 20 pieces of 2.2uF ,1210,100V,X7R Flexiterm ceramic capcaitors. (since the Vin is 33 to 43v).
However, in the first instance, we are just doing a test board, (as in the attached schem), and since the test board is likely to get bent and bashed about, we don’t want 1210 ceramic caps on it, which may break.
Therefore, for the test board, we have used a parallel combination of 5 pieces of 1uF, 0805,100V,X7R capacitors, in parallel with 5 pieces of radial ceramic capacitors, in parallel with one 10uF,100V radial film capacitor……..this doesn’t quite add up to 20uF…..however, its cheaper than 20 Flexiterm caps, and more resilient to capacitor cracking………also, since the test board is simply to proove that our external error amplifier correctly clamps the output current to 6.5A, we believe this “alternative” input capacitor bank, will be satisfactory for use.
Would you agree, that since our testing will not involve load transients, we will be ok not using the 20uF of SMD ceramic capacitance? (which the datasheet asks for on pg 21)
The Vicor “DCM design guide”, on page 23, actually calls for the input ceramic capacitor bank to have an SRF higher than the DCDC module switching frequency (1MHz)……so we have violated this, but again, since our test will not involve load transients, can you confirm that our alternative input filter (as in the attached schem), will be fine?
DCM36623T50M53C2T00 datasheet
https://www.vicorpower.com/documents/datasheets/DCM3623x50M53C2yzz_ds.pdf
We are using the DCM36623T50M53C2T00 DCDC module from Vicor.
Page 21 of its datasheet says that the downstream part of the input filter should be 20uF of ceramic capacitance..
..We agree that ceramic SMD capacitance is needed because otherwise there may be instability when the load has heavy transient behaviour. So the filter will need to comprise 20 pieces of 2.2uF ,1210,100V,X7R Flexiterm ceramic capcaitors. (since the Vin is 33 to 43v).
However, in the first instance, we are just doing a test board, (as in the attached schem), and since the test board is likely to get bent and bashed about, we don’t want 1210 ceramic caps on it, which may break.
Therefore, for the test board, we have used a parallel combination of 5 pieces of 1uF, 0805,100V,X7R capacitors, in parallel with 5 pieces of radial ceramic capacitors, in parallel with one 10uF,100V radial film capacitor……..this doesn’t quite add up to 20uF…..however, its cheaper than 20 Flexiterm caps, and more resilient to capacitor cracking………also, since the test board is simply to proove that our external error amplifier correctly clamps the output current to 6.5A, we believe this “alternative” input capacitor bank, will be satisfactory for use.
Would you agree, that since our testing will not involve load transients, we will be ok not using the 20uF of SMD ceramic capacitance? (which the datasheet asks for on pg 21)
The Vicor “DCM design guide”, on page 23, actually calls for the input ceramic capacitor bank to have an SRF higher than the DCDC module switching frequency (1MHz)……so we have violated this, but again, since our test will not involve load transients, can you confirm that our alternative input filter (as in the attached schem), will be fine?
DCM36623T50M53C2T00 datasheet
https://www.vicorpower.com/documents/datasheets/DCM3623x50M53C2yzz_ds.pdf