JAJSFQ6E March 2014 – July 2018 TPS92601-Q1 , TPS92602-Q1
UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.
The TPS92602y-Q1 device drives a ground-referenced N-channel FET. The breakdown voltage is the output voltage plus any voltage spike, with 30% added for a safety margin as shown in Equation 68.
Select an N-channel FET with breakdown voltage of 50 V.
Estimate the rDS(on) and gate charge based on the desired efficiency target.
For a target of 92% efficiency with a 16-V input voltage at 1 A, maximum power dissipation is limited to 1.148 W. The main power-dissipating devices are the MOSFET, inductor, diode, current-sense resistor and the integrated circuit, the TPS92602y-Q1 device.
This assumption leaves 600 mW of power dissipation for the MOSFET. Allowing half for conduction and half for switching losses, we can determine a target rDS(on) and Q(GS) for the MOSFET by Equation 71 and Equation 72.
Calculate a target MOSFET gate-to-source charge of less than 28.3 nC to limit the switching losses to less than 200 mW.
Selecting a target MOSFET rDS(on) of 26.7 mΩ limits the conduction losses to less than 250 mW.