Understanding Modern Power MOSFETs - Fairchild Semiconductor

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23 24 1x Die Comparison: Planar versus Charge Balance MOSFET 1x QFET C-series Gate Voltage • A MOSFET will turn on if the gate voltage is somewhat larger than a parameter known as the threshold voltage, VTH • As RDS(ON) decreases with increasing VGS , it is advantageous to drive the MOSFET gate much higher than the threshold voltage 0.65x Die Shrink, 35% @ same drain current 0.65x SuperFET I load Gate voltage applied to turn device on V ds Load resistor 12
25 DC Characteristics • The transfer and saturation characteristics show the relationship between VGS , ID and VDS • If not otherwise specified, the forward transconductance, gm, which is the incremental change in ID per change in VDS , can be determined from the transfer characteristics • The saturation characteristics show the boundary between linear and saturation modes, and can also be used to estimate gm • In saturation mode, I D = gm(V GS -V TH ): used when considering switching 26 Transfer characteristics Saturation characteristics Maximum Permitted Gate Voltage • The maximum permitted gate voltage, VGS max is specified in the absolute maximum ratings of the datasheet • If this value is exceeded, the MOSFET will be destroyed • Oscillation on the gate can lead to transient voltages, which could exceed VGS max and therefore destroy the gate • Pay particular attention to the gate drive layout • Keep the gate drivers very close to the gate • If using negative gate drive on the MOSFET, which we generally do not recommend, note that the V DS max rating will also be reduced by the amount of the negative gate drive 13
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: 21 22 Source Technology Trends: R D
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 and 30: 57 58 FDD26AN06A0 26 mΩ, Q g = 17
Page 31 and 32: 61 Synchronous Buck Topology • Ou
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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