Understanding Modern Power MOSFETs - Fairchild Semiconductor

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59 Safe Operating Area • During switching (at the end of the second stage), we have a peak power dissipation of 2000W •VDS = 50V •ID = 40A • The safe operating area plots shows which voltages and currents can be sustained for which time, if TJ max is not exceeded 60 Gate Oscillation Revisited Forward Bias Safe Operating Area • Earlier we noted that gate oscillation can cause an overshoot on the gate, which could destroy the silicon • A second problem with gate oscillation is that the maximum current and maximum voltage point of the safe-operating area will be crossed multiple times • This could destroy the part, or at best, greatly increase the switching losses 30
61 Synchronous Buck Topology • Our session objective was to understand MOSFET selection for the synchronous buck topology • The synchronous buck topology output stage is similar to a classical PWM output stage on a microcontroller followed by a filter • The duty cycle D is controlled to give the right output voltage • In steady state D = Vout / Vin V in • In the steady state condition, consider the case with the high side device ON • The low side device is OFF • Current flows through the high side device into the inductor 62 V in Synchronous Buck Topology High Side On V out V s V in Both Off V out V out • The high side device switches OFF • As the low side device is OFF, the inductor current will be taken up by the low side diode • The switching node voltage V s is therefore NEGATIVE 31
Page 1 and 2: 1 2 Understanding Modern Power MOSF
Page 3 and 4: 5 Introducing the P-channel MOSFET
Page 5 and 6: Design challenges •Size • Power
Page 7 and 8: V gs FDS6688S 13 14 V ds FDS6688S E
Page 9 and 10: 17 18 Example: FDD16AN080AN R DS(ON
Page 11 and 12: 21 22 Source Technology Trends: R D
Page 13 and 14: 25 DC Characteristics • The trans
Page 15 and 16: 29 30 Selection and Thermal Calcula
Page 17 and 18: PCB Package 33 34 Simple Thermal Mo
Page 19 and 20: 37 38 FDD26AN06A0 26 mΩ, 2 o C/W
Page 21 and 22: 41 42 The Importance of Avalanche C
Page 23 and 24: 45 46 FDD26AN06A0 26 mΩ, I as = 2
Page 25 and 26: 49 Second Stage of Switching • Wh
Page 27 and 28: 53 Final Stage of Switching • The
Page 29: 57 58 FDD26AN06A0 26 mΩ, Q g = 17
Page 33 and 34: 65 V IN Synchronous Buck Switches
Page 35 and 36: 69 Selecting Power MOSFETs for Sync

Understanding Modern Power MOSFETs - Fairchild Semiconductor

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