Application Note AN-LV-11-2013-V1.0-EN-059 Selecting P-channel MOSFETs for Switching Applications IFAT PMM APS SE DC Pradeep Kumar Tamma Application Note Selecting P-channel MOSFETs for Switching Applications AN-LV-11-2013-V1.0-EN-059 Edition 2013-11-26 Published by Infineon Technologies Austria AG 9500 Villach, Austria © Infineon Technologies Austria AG 2016. All Rights Reserved. Attention please! THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT. THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. 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Life support devices or systems are intended to be implanted in the human body, or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. AN-LV-10-2013-V1.0-EN-059 Revision History: 13-11-25, V1.0 Subjects: Application Note initialized Authors: IFAT PMM APS SE DC, Pradeep Kumar Tamma We Listen to Your Comments Any comments with regards to this document or topic would be highly appreciated. Please contact author at [email protected] 2 Application Note Selecting P-channel MOSFETs for Switching Applications AN-LV-11-2013-V1.0-EN-059 Table of contents 1 Introduction .................................................................................................................................................. 4 2 Comparison between P-channel and N-channel MOSFETs in an application ...................................... 4 3 Choosing a P-channel MOSFET for an application ................................................................................. 4 3.1 Low-Voltage Drives ............................................................................................................................ 5 3.2 Non-isolated Point of Loads ............................................................................................................... 7 4 Conclusion ................................................................................................................................................... 8 3 Application Note Selecting P-channel MOSFETs for Switching Applications 1 AN-LV-11-2013-V1.0-EN-059 Introduction P-channel MOSFETs are often used for load switching. The simplicity of P-channel solutions on the high side makes them equally attractive for applications such as Low-Voltage Drives and non-isolated Point of Loads in systems where space is at a premium. The main advantage of a P-channel MOSFET is the simplified gate driving technique in the high side switch position and often reduces the overall cost. This application note discusses the advantages of P-channel MOSFETs as a high side switch in these applications. 2 Comparison between P-channel and N-channel MOSFETs in an application The source voltage of an N-channel MOSFET when used as a high side switch will be at a higher potential with respect to ground. Thus, to drive an N-channel MOSFET an isolated gate driver or a pulse transformer must be used. The driver requires an additional power supply whilst the transformer can sometimes produce incorrect conditions. However, this is not the case with P-channel. It is easy to drive a P-channel high side switch with a very simple level shifter circuit. Doing this simplifies the circuit and often reduces the overall cost. However, the point to be noted here is that it is not possible to achieve the same R DS(on) performance for a P-channel MOSFET as for an N-channel with the same chip size. As the mobility of the carriers in an N-channel is approximately 2 to 3 times higher than that of a P-channel, for the same RDS(on) value, the P-channel chip must be 2 to 3 times the size of the N-channel. Because of the larger chip size, the P-channel device will have a lower thermal resistance and a higher current rating but its dynamic performance will be affected proportionally by the chip size. So, in a low frequency application where the conduction losses are prominent, a P-channel MOSFET should have a comparable RDS(on) to that of an N-channel. In this case, the P-channel MOSFET chip area will be larger than that of the N-channel. Also, in high frequency applications where the switching losses are dominant, a P-channel MOSFET should have similar total gate charges to that of an N-channel. In this case, a P-channel MOSFET has a similar chip size but a lower current rating than that of an N-channel. Thus a suitable P-channel MOSFET must be carefully selected taking into consideration the appropriate RDS(on) and gate charge. 3 Choosing a P-channel MOSFET for an application There are several switching applications that can benefit from the use of P-channel MOSFETs such as Low-Voltage Drives and non-isolated Point of Loads. In these applications the key parameters driving the MOSFET selection are device on-resistance (RDS(on)) and the gate charge (QG). One or other of these parameters becomes more important depending on the switching frequency in the application. 4 Application Note Selecting P-channel MOSFETs for Switching Applications 3.1 AN-LV-11-2013-V1.0-EN-059 Low-Voltage Drives In Low-Voltage Drive applications the N-channel MOSFETs are often used in a full-bridge or B6-bridge configuration with the motor and a DC source. The trade-off for the advantages offered by N-channel devices is the increasing gate driver design complexity. A gate driver of an N-channel high side switch requires a bootstrap circuit that produces a gate voltage above the motor voltage rail or an isolated power supply to turn it on. Greater design complexity usually results in increased design effort and greater space consumption. Figure 3.1 below shows the difference between the circuit with complementary MOSFETs and the circuit with N-channel ones. In this configuration, when the high side switch is realized with a P-channel MOSFET, the driver design will be simplified enormously. No charge pump is required for driving the high side switch; it can easily be driven by the MCU via a level shifter. In Low-Voltage Drive applications the N-channel MOSFETs are often used in a full-bridge or B6-bridge configuration with the motor and a DC source. The trade-off for the advantages offered by N-channel devices is the increasing gate driver design complexity. A gate driver of an N-channel high side switch requires a bootstrap circuit that produces a gate voltage above the motor voltage rail or an isolated power supply to turn it on. Greater design complexity usually results in increased design effort and greater space consumption. Figure 3.1 below shows the difference between the circuit with complementary MOSFETs and the circuit with N-channel ones. In this configuration, when the high side switch is realized with a P-channel MOSFET, the driver design will be simplified enormously. No charge pump is required for driving the high side switch; it can easily be driven by the MCU via a level shifter. Figure 3.1: Low-Voltage drive application circuit 5 Application Note Selecting P-channel MOSFETs for Switching Applications AN-LV-11-2013-V1.0-EN-059 Generally the switching frequencies in a Low-Voltage Drive application will be between 10 to 50kHz. At these frequencies, most of the power dissipation of a MOSFET is dominated by conduction losses due to the high currents of the motor. Thus, in this application a P-channel MOSFET with comparable RDS(on) has to be selected to get the maximum advantage of using a P-channel. This can be explained by considering an example of a 30W LowVoltage Drive powered by a 12V battery. For a high side P-channel MOSFET there can be two options - one with comparable RDS(on) as that of the low side N-channel and one with comparable gate charges. Table 3.1 below shows the parts considered for the full bridge Low-Voltage Drive with similar RDS(on) and with similar gate charges as that of the N-channel MOSFET on the low side. Package VDS,max [V] RDS (on),max [mΩ] ID,max [A] QG [nC] Ptot,max [W] Rth,JC [K/W] BSZ088N03LS G S3O8 30 8.8 40 16.0 35 3.6 BSZ086P03NS3 G S3O8 -30 8.6 -40.0 43.2 69 1.8 BSZ180P03NS3 G S3O8 -30 18.0 -39.6 20.0 40 3.1 Table 3.1: Parts considered for the application The losses of the MOSFETs in the application are shown in Table 3.2 below. BSZ088N03LS G BSZ086P03NS3 G BSZ180P03NS3 G Conduction Losses [mW] 220 215 450 Switching Losses [mW] 14.1 33.9 22.0 Total MOSFET Losses [mW] 234.1 248.9 472.0 Table 3.2: MOSFET losses in the application From Table 3.2: MOSFET losses in the application it is clear that the total power losses are dominated by the conduction losses as shown in the pie chart below. It is also clear that if the P-channel MOSFET is chosen with similar gate charges as that of the N-channel the switching losses will be comparable but the conduction losses will be too high. Thus for the applications with low switching frequencies the high side P-channel MOSFET has to have a comparable RDS(on) as that of the low side N-channel. Figure 3.2: MOSFET losses in the application 6 Application Note Selecting P-channel MOSFETs for Switching Applications 3.2 AN-LV-11-2013-V1.0-EN-059 Non-isolated Point of Loads Low power non-isolated Point of Loads where the output power is less than 10W, represents one of the biggest design challenges. Size must be kept to a minimum while maintaining an acceptable level of efficiency. One common way to reduce converter size is to specify a higher operating frequency. Faster switching means a smaller inductor can be used. Schottky diodes are sometimes used for synchronous rectification in these circuits but MOSFETs are a better choice as output voltages decrease, since the voltage drop can be significantly less than with a diode. An additional space-saving technique is to replace the high side N-channel MOSFET with a P-channel. The P-channel approach eliminates the need for complex additional circuitry to drive the gate, as required when a N-channel MOSFET is used on the high side. Figure 3.2 below shows the basic circuit diagram of a buck converter with a P-channel MOSFET on the high side. Figure 3.3: Buck converter circuit 7 Application Note Selecting P-channel MOSFETs for Switching Applications AN-LV-11-2013-V1.0-EN-059 Generally the switching frequencies in non-isolated Point of Load applications will be around 500kHz even sometimes up to 2MHz. In contradiction to previous applications, at these frequencies, the dominating loss component is the switching loss. Figure 3.3 below shows the loss contribution of the MOSFET in a 3 watt non-isolated Point of Load application operating at 1MHz. Figure 3.4: MOSFET losses in low power Buck Converters Thus a high side P-channel MOSFET with comparable gate charge to that of the low side N-channel MOSFET has to be selected. 4 Conclusion Using a P-channel MOSFET clearly offers designers benefits in terms of easier, more reliable and more optimized circuit design. For given applications, the trade-off between RDS(on) and QG must be evaluated when selecting a P-channel MOSFET in order to achieve optimal performance. Infineon offers a wide range of P-channel MOSFETs both in small signal and power packages. Table 4.1 & Table 4.2 below shows the Infineon P-channel MOSFET portfolio. 8 Application Note Selecting P-channel MOSFETs for Switching Applications SPB08P06P G SPB18P06P G SPB80P06P G SPD04P10P G SPD04P10PL G SPD15P10P G IPD042P03L3 G SPD08P06P G SPD09P06PL G SPD18P06P G SPD30P06P G IPD068P03L3 G SPD15P10PL G SPD50P03L G BSZ086P03NS3 G BSZ086P03NS3E G BSZ120P03NS3E G BSZ180P03NS3E G BSZ180P03NS3 G BSZ120P03NS3 G BSO130P03S BSO613SPV G BSO080P03NS3 G BSO201SP H BSO207P H BSO303P H BSO303SP H BSO211P H BSO301SP H BSO080P03S H BSO200P03S H BSO203P H BSO203SP H BSO080P03NS3E G BSO130P03S H BSC080P03LS G BSC130P03LS G BSC200P03LS G BSC030P03NS3 G BSC060P03NS3E G BSC084P03NS3 G BSC084P03NS3E G SPP08P06P H SPP15P10PL H SPP18P06P H SPP80P06P H SPP15P10P H AN-LV-11-2013-V1.0-EN-059 Package VDS,max [V] RDS (on),max [mΩ] ID,max [A] Ptot,max [W] QG [nC] Rth,JC [K/W] D2PAK (TO-263) D2PAK (TO-263) D2PAK (TO-263) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK 5pin (TO-252 5pin) S3O8 S3O8 S3O8 S3O8 S3O8 S3O8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 TO-220 TO-220 TO-220 TO-220 TO-220 -60 -60 -60 -100 -100 -100 -30 -60 -60 -60 -60 -30 -100 -30 -30 -30 -30 -30 -30 -30 -30 -60 -30 -20 -20 -30 -30 -20 -30 -30 -30 -20 -20 -30 -30 -30 -30 -30 -30 -30 -30 -30 -60 -100 -60 -60 -100 300 130 23 1000 850 240 4.2 300 250 130 75 6.8 200 7 8.6 8.6 12 18 18 12 13 130 8 12.9 70 21 21 110 8 8 20 34 34 8 13 8 13 20 3 6 8.4 8.4 300 200 130 23 240 -8.8 -18.6 -80 -4 -4.2 -15 -70 -8.83 -9.7 -18.6 -30 -70 -15 -50 -40 -40 -40 -39.6 -39.6 -40 -11.3 -3.44 14.8 -14.9 -5.7 -8.2 -9.1 -4.6 -14.9 -14.9 -9.1 -8.2 -9 14.8 -11.7 -30 -22.5 -12.5 -100 -100 -78.6 -78.6 -8.8 -15 -18.6 -80 -15 42 80 375 38 38 128 150 42 42 80 125 100 128 150 69 69 52 40 40 52 1.56 2.5 1.6 2.5 1.6 2 1.56 1.6 1.79 1.79 1.56 2 2.35 1.6 1.56 89 69 63 125 83 69 69 42 128 80 340 128 -10 -22 -115 -9 -12 -37 -131 -10 -14 -22 -32 -68 -47 -95 -43.2 -43.2 -30 -20 -20 -30 -61 -20 -61 -66 -12 -36 -40 -8 -102 -102 -40 -32.4 -33.6 -61 -61 -92 -54.9 -36.4 -137 -61 -43 -43 -10 -47 -22 -115 -37 3.6 1.85 0.4 3.9 3.9 1.17 1 3.6 3.6 1.85 1.2 1.5 1.17 1 1.8 1.8 2.4 3.1 3.1 2.4 110 100 110 110 110 110 110 110 110 110 110 110 110 110 110 50 1.8 2 1 1.5 1.8 1.8 3.6 1.17 1.85 0.4 1.17 Table 4.1: P-channel Power MOSFET portfolio 9 Application Note Selecting P-channel MOSFETs for Switching Applications SPB08P06P G SPB18P06P G SPB80P06P G SPD04P10P G SPD04P10PL G SPD15P10P G IPD042P03L3 G SPD08P06P G SPD09P06PL G SPD18P06P G SPD30P06P G IPD068P03L3 G SPD15P10PL G SPD50P03L G BSZ086P03NS3 G BSZ086P03NS3E G BSZ120P03NS3E G BSZ180P03NS3E G BSZ180P03NS3 G BSZ120P03NS3 G BSO130P03S BSO613SPV G BSO080P03NS3 G BSO201SP H BSO207P H BSO303P H BSO303SP H BSO211P H BSO301SP H BSO080P03S H BSO200P03S H BSO203P H BSO203SP H BSO080P03NS3E G BSO130P03S H BSC080P03LS G BSC130P03LS G BSC200P03LS G BSC030P03NS3 G BSC060P03NS3E G BSC084P03NS3 G BSC084P03NS3E G SPP08P06P H SPP15P10PL H SPP18P06P H SPP80P06P H SPP15P10P H AN-LV-11-2013-V1.0-EN-059 Package VDS,max [V] RDS (on),max [mΩ] ID,max [A] Ptot,max [W] QG [nC] Rth,JC [K/W] D2PAK (TO-263) D2PAK (TO-263) D2PAK (TO-263) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK (TO-252) DPAK 5pin (TO-252 5pin) S3O8 S3O8 S3O8 S3O8 S3O8 S3O8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 SuperSO8 TO-220 TO-220 TO-220 TO-220 TO-220 -60 -60 -60 -100 -100 -100 -30 -60 -60 -60 -60 -30 -100 -30 -30 -30 -30 -30 -30 -30 -30 -60 -30 -20 -20 -30 -30 -20 -30 -30 -30 -20 -20 -30 -30 -30 -30 -30 -30 -30 -30 -30 -60 -100 -60 -60 -100 300 130 23 1000 850 240 4.2 300 250 130 75 6.8 200 7 8.6 8.6 12 18 18 12 13 130 8 12.9 70 21 21 110 8 8 20 34 34 8 13 8 13 20 3 6 8.4 8.4 300 200 130 23 240 -8.8 -18.6 -80 -4 -4.2 -15 -70 -8.83 -9.7 -18.6 -30 -70 -15 -50 -40 -40 -40 -39.6 -39.6 -40 -11.3 -3.44 14.8 -14.9 -5.7 -8.2 -9.1 -4.6 -14.9 -14.9 -9.1 -8.2 -9 14.8 -11.7 -30 -22.5 -12.5 -100 -100 -78.6 -78.6 -8.8 -15 -18.6 -80 -15 42 80 375 38 38 128 150 42 42 80 125 100 128 150 69 69 52 40 40 52 1.56 2.5 1.6 2.5 1.6 2 1.56 1.6 1.79 1.79 1.56 2 2.35 1.6 1.56 89 69 63 125 83 69 69 42 128 80 340 128 -10 -22 -115 -9 -12 -37 -131 -10 -14 -22 -32 -68 -47 -95 -43.2 -43.2 -30 -20 -20 -30 -61 -20 -61 -66 -12 -36 -40 -8 -102 -102 -40 -32.4 -33.6 -61 -61 -92 -54.9 -36.4 -137 -61 -43 -43 -10 -47 -22 -115 -37 3.6 1.85 0.4 3.9 3.9 1.17 1 3.6 3.6 1.85 1.2 1.5 1.17 1 1.8 1.8 2.4 3.1 3.1 2.4 110 100 110 110 110 110 110 110 110 110 110 110 110 110 110 50 1.8 2 1 1.5 1.8 1.8 3.6 1.17 1.85 0.4 1.17 Table 4.2: P-channel Small Signal MOSFET portfolio 10