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There are going to be times when the parts available or accessible aren't exactly what is specified by the BOM. Here are some part numbers that we have verified to be acceptable substitions.
The most important specification for the Q2 MOSFET is the power drop when under load, found on datasheets as Rds as the resistance at a voltage and current. Compare the Rds for the suitable parts to your own to estimate whether it may work or not, and if it does, let us know in the discussion forum and we'll get some measurements and add them here!
WARNING: The BOM for 2.6 specified a IRFR5305 but we've now found this to be unacceptable due to the power drop.
| Part Number | Voltage Drop @ 5V / 1A | Suitable? |
|---|---|---|
| IRFR5305 | 240 mv | NO |
| TJ40S04M3L | 11 mV | YES |
| SQD50P03 | 8 mV | YES |
| IPD042P03L3GATMA1 | 4 mV | YES |
| IPD068P03L3G (Infineon) | 7 mV | YES |
| IPD068P03L3G UMW (Youtai Semiconductor) | 7 mV | YES |
Note: Measurements were taken from Pin 1 of J2 to the 5V out on Q2.
Interestingly, Pin 1 to 5V in (via a screw terminal introduces a 3 mV drop all on it's own under 1A of draw, so it goes to show just how good the devices above work! 👍
For those who aren't in Germany, Kessler might not be familiar.
In the BOM there may be a Kessler column. If you search Kessler's website for the part number found in the BOM, for instance 511511, you'll find the part and the specifications. You can then use those specifications to find an alternative by comparing values found on a datasheet to these values.