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FET power dissipation

A project log for USB-C Power Delivery Sink (BCR)

A USB-C PD Sink up to 20V 5A based on the Cypress CYPD3177 USB PD Controller

MagicWolfiMagicWolfi 12/13/2019 at 18:380 Comments

The switching FET in this circuit has to carry up to 5A, which is significant. Thus the drain source resistance Rds-on is important to be minimized and power dissipation through the package needs to be calculated. Here are some test results, in the form of voltage drop over the dual DS junctions.

U load [V] I load [A]V drain-source x2 [mV]Tjunction [degC]P diss [mW]Rdson [mOhm]
5.071.2756.529.572
22
9.032.26  
61.633.7139
14
11.983.00
89.541.8268
15
14.623.66
106.549.3389
15
19.674.92
141.068.3693
14

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