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FDS4953 データシート(PDF) 11 Page - Microsemi Corporation |
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FDS4953 データシート(HTML) 11 Page - Microsemi Corporation |
11 / 18 page LXE1710 EVALUATION BOARD USER GUIDE Microsemi Linfinity Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11 Copyright © 2000 Rev. 1.1, 2000-12-01 MOSFET SELECTION As seen in previous sections, the user can design the output filter of the amplifier to meet performance or costs targets. In addition, the amplifier’s power stage (selection of MOSFETs) can be selected depending on these tradeoffs. The efficiency of the amplifier circuit can be approximated by the following equation. CROSS L IND PDS NDS L IN OUT P R R R R I R I P P + + + + = = ] ) ( 2 [ 2 2 Where RL = DC Resistance of Speaker RNDS = n-channel MOSFET on-resistance RPDS = p-channel MOSFET on-resistance RIND = DC Resistance of Inductor PCROSS = MOSFET Switching Loss The overall efficiency is a function of primarily the MOSFETs and output filter inductors. The “Inductor” section’s contribution will be considered later. The MOSFET Power loss is a function of the on-resistance and gate charge. A R P I W P R R I P O PDS NDS DS 5 . 2 4 25 Then 4 at 25 If )] ( 2 [ Loss Power MOSFET 2 = = = Ω = + = = The LX1710 Evaluation Board is designed using FDS4953 p-channel and FDS6612A n-channel MOSFETS. W P R R DS PDS NDS 56 . 1 )] 095 . 0 03 . 0 ( 2 [ ) 5 . 2 ( 095 . 0 , 03 . 0 2 = + = Ω = Ω = MOSFET power loss is proportional to on-resistance. n f CV P S CROSS 2 Loss Switching MOSFET = = Where C = Input Capacitance V = Supply Voltage fS = Switching Frequency n = Number of MOSFETS Assume C = 1000pF V = 15VDC fS = 500kHz W PCROSS 45 . 0 ) 4 )( 10 500 )( 15 )( 10 1 ( 3 2 9 = × × = − MOSFET switching loss is proportional to total gate charge, supply voltage, and switching frequency. There are a few other important parameters to consider when selecting the output power components besides the on-resistance and gate charge of the MOSFETs. The drain-source voltage must provide ample margin for circuit noise and high speed switching transients. Since the amplifier configuration requires output bridge operation at the supply voltage, the MOSFETs should have a drain-source voltage of at least 50% greater than the supply voltage. The power dissipation of the MOSFETs should also be able to dissipate the heat generated by the internal losses and be greater than the sum of PDS and PCROSS. Linfinity recommends that in selecting MOSFETs, RDS 0 1!1 2g <10nC. The table below provides several MOSFET options . FDS6612A FDS4953 Si4532ADY IRF7105 n-channel p-channel n-channel p-channel n-channel p-channel Drain-Source On-Resistance RDS(ON)@VGS = +/-10V 0.022 0.053 0.053 0.08 0.10 0.25 Drain-Source Voltage VDSS (V) 30 -30 30 -30 25 -25 Drain Current (continuous) ID(continuous) (A) 8.4 -5 4.9 -3.9 3.5 -2.3 Total Gate Charge Qg (typical) (nC) 9 8 8 10 9.4 10 Manufacturer Fairchild Fairchild Vishay Siliconix Vishay Siliconix International Rectifier International Rectifier MOSFET Component Options |
同様の部品番号 - FDS4953 |
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同様の説明 - FDS4953 |
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