Application Note Selecting P-Channel MOSFETs for Switching Applications

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.
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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
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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
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