Automotive MOSFETs Datasheet Explanation

Data Sheet Explanation
V1.2 2014-04
Edition 2014-01
Published by Infineon Technologies AG,
81726 Munich, Germany.
© 2014 Infineon Technologies AG
All Rights Reserved.
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Document Change History
Date
Version
Changed By
Change Description
01/2014
V1.1
MP
Update of formula 1
01/2014
V1.2
MP
Update of formula 1
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Application Note
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Abstract
Table of Contents
Table of Contents .................................................................................................................................................4
1
Abstract ............................................................................................................................................5
2
Introduction ......................................................................................................................................6
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
Datasheet Parameters .....................................................................................................................7
Power dissipation...............................................................................................................................7
Drain current ......................................................................................................................................8
Safe operating area ...........................................................................................................................9
Maximum transient thermal impedance ZthJC ...................................................................................10
Typical output characteristics...........................................................................................................11
Drain-source on-state resistance as a function of Drain current ......................................................12
Transfer characteristics....................................................................................................................13
Drain-source on-state resistance .....................................................................................................14
Gate threshold voltage.....................................................................................................................15
Capacitances ...................................................................................................................................16
Reverse diode characteristics..........................................................................................................17
Avalanche characteristics ................................................................................................................19
Avalanche energy ............................................................................................................................19
Drain-source breakdown voltage .....................................................................................................21
Typical gate charge..........................................................................................................................22
Leakage Currents ............................................................................................................................23
Switching Times...............................................................................................................................23
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Abstract
1
Abstract
The following information is given as a hint for the implementation of the device only and shall not be
regarded as a description or warranty of a certain functionality, condition or quality of the device.
This Application Note is intended to provide an explanation of the parameters and diagrams given in the
datasheet of automotive low voltage MOSFETs. With the application note the designer of ECUs requiring a low
voltage MOSFET is able to use the datasheet in the right way and will be provided with background information.
Application Note
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Introduction
2
Introduction
Each parameter mentioned in the datasheet gives values which characterizes the device as detailed as
possible.
With this information the designer should be able on the one hand to compare devices from different
competitors with each other; on the other hand the information should be sufficient to figure out where the limits
of the device are.
This document helps to understand the datasheet parameter and characteristics much better. It explains the
interaction between the parameters and the influence of the conditions as temperature or gate voltage.
Application Note
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Datasheet Parameters
3
Datasheet Parameters
The attached diagrams, tables and explanations are referring to the datasheet of IPD90N06S4-04 (rev.1.0 from
2008-03-7) as example. The shown values and characteristics are not feasible to use for design-in activities. For
the latest version of datasheets please refer to our webpage (www.infineon.com/optimos-T).
3.1
Power dissipation
This parameter describes
(Figure 1, Figure 2).
the
maximum
feasible
power
dissipation
over
the
case
temperature
The power dissipation of the MOSFET is directly related to the chip size of the device (eq.(1)). Up to a junction
o
temperature of 25 C, the power dissipation is specified at its maximum value (eq.(2)). With increasing case
temperature the power dissipation is decreasing according to:
TJ  TC
RthJC
(1)
Ptot (TC ) 
(2)
Ptot (max) 
(175  25) K
 188W
0.8 K
W
Figure 1
Maximum ratings for Ptot (datasheet)
Figure 2
Power dissipation Ptot = f(TC)
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Datasheet Parameters
3.2
Drain current
The datasheet specifies a maximum continuous drain current ID and a pulsed drain current ID,pulse (Figure 3). The
maximum continuous drain current depends on the maximum power dissipation (chapter 3.1) and is defined by
the temperature difference junction to case, the thermal resistance RthJC and the on-state resistance RDS(on) at
maximum junction temperature (eq.(3)). Please refer to chapter 3.8 for calculating the temperature dependency
of the on-state resistance.
(3)
I D (TC ) 
TJ  TC
RthJC
RDS ( on ) _ TJ (max)
I D (max) 
(175  25) K
0.8 K
W  169 A
6.6m
Additional boundary conditions as bondwire diameter, chip design and assembly are limiting the maximum drain
current to the given value (Figure 4).
Figure 3
Maximum ratings for ID (datasheet)
Figure 4
Drain current ID = f(TC)
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Datasheet Parameters
3.3
Safe operating area
This diagram shows the drain current ID as a function of the drain-source voltage VDS with the condition of
different pulse lengths.
There are several limitations in this diagram:
A)
The top limit is related to the maximum pulsed drain current.
B)
This area is limited by the on-state resistance RDS(on) at maximum junction temperature.
C)
In this area a so-called constant power line will be observed. Depending on the pulse length of the applied
power pulse, the thermal impedance changes and leads to different maximum power losses. For a given
pulse length, the thermal impedance ZthJC has to be determined by looking at the diagram “Maximum
transient thermal impedance” (chapter 3.4).
(4)
D)
I D (VDS ) 
TJ  TC
VDS * Z thJC
In linear operations there is a risk for getting hot spots at low gate-source voltages due to the negative
temperature characteristic in the transfer characteristic. This effect becomes more important for latest
trench technologies with high current densities, where the “zero temperature coefficient” point of the
transfer characteristic is shifted to higher drain currents. For more details please refer to application note
“Automotive MOSFETs in Linear Applications: Thermal Instability”, available at www.infineon.com .
In order to consider the hot spot effect for higher VDS and longer pulse times, the SOA characteristic is
showing a different slope in that region.
E)
The maximum breakdown voltage V(BR)DSS is determined by the technology and limits the diagram on the
right hand side.
(A)
(C)
(B)
(D)
(E)
Figure 5
Safe operating area ID=f(VDS)
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Datasheet Parameters
3.4
Maximum transient thermal impedance ZthJC
RthJC is the thermal resistance from the junction of the die to the outside of the device. The heat is generated by
the power loss in the device itself and the thermal resistance relates how hot the chip gets relative to the case.
Transient thermal impedance takes into account the heat capacity of the device, so it can be used to estimate
directly temperatures resulting from power loss on transient base.
Figure 6
Maximum transient thermal impedance ZthJC=f(tp)
The diagram (Figure 6) shows the variation of the thermal resistance ZthJC for the specified pulse duty factor
D=tp/T as a function of the loading time tp (pulse width).
To dissipate the heat out of the device, it has to pass several different layers with its characteristic thermal
resistances and thermal capacitances. This results in the fact that depending on the pulse length either the
thermal resistance or the thermal capacitance is dominating the behavior of the device. The increase of the
junction temperature can be calculated as shown in equation (5). In a thermal equilibrium before applying the
power pulse is TJ,start = TC.
(5)
Figure 7
TJ  TJ , start  TJ  TJ , start  Z thJC (t P , D)  Ptot
Thermal characteristics
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Datasheet Parameters
3.5
Typical output characteristics
Those characteristic (Figure 8) is showing the typical dependence of the drain current I D as function of the drainsource voltage VDS at a given gate-source voltage VGS. The chip temperature TJ is specified as well.
Ohmic
region
Figure 8
Typical output characteristics ID=f(VDS)
The MOSFET should be operated in the “ohmic” region as shown in Figure 8. There is a maximum drain current
for a corresponding gate-source voltage that a MOSFET will conduct. If the operating point at a given gatesource voltage goes above the “ohmic”region, any further increase in drain current leads to a significant rise in
drain-source voltage (linear operation mode) and a consequent rise in conduction loss. If the power dissipation
will not be limited in value and time, the device might be failing.
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Datasheet Parameters
3.6
Drain-source on-state resistance as a function of Drain current
The Drain Source on-state resistance as a function over the Drain current with Gate Source voltage as a
parameter can be directly calculated out of the typical output characteristic diagram.
(6)
Figure 9
R DS ( on ) ( I D ) 
VDS
ID
Typical drain-source on-state resistance RDS(on)=f(ID)
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Datasheet Parameters
3.7
Transfer characteristics
This diagram is showing the typical Drain current as a function of the applied Gate to Source voltage. The graph
is given at three different junction temperatures. Normally all the graphs are intersecting at one point, the so
called temperature stable operating point.
If the Gate to Source voltage applied to the MOSFET is below that point (in the example V GS < 6.2V), the
MOSFET will operate with a positive temperature coefficient, meaning with increased junction temperature, the
Drain current will increase as well. This operation condition is not preferable due to a possible thermal runaway.
Above the temperature stable operation point, the temperature coefficient is negative, meaning with increasing
junction temperature the Drain current decreases. The MOSFET will limit its current handling capability at high
temperatures itself. The operation in that range is uncritical (as long as the junction temperature stays within
specification).
Figure 10
Typical transfer characteristics ID=f(VGS)
To have a first idea about the max or min rating of that behavior, the curves can be moved in parallel according
the min and max ratings of the threshold voltage (for a normal level device +/- 1V).
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Datasheet Parameters
3.8
Drain-source on-state resistance
The drain-source on-state resistance is one of the key parameters of a MOSFET. In the data sheet there are
two sections dealing with this resistance. In the table of the data sheet, typ. and max ratings at room
temperature are given. This value is tested during production at the specified conditions.
For data sheets including Trough Hole and SMD devices, the RDSon is separately mentioned. For an SMD device
the resistance is measured between the Source Pin and the Drain backside of the device. For a Trough Hole
package, the RDSon is specified between the Drain and Source Pin of the package at a defined soldering point
(for TO-220 approximately 4.5 mm lead lengths) resulting in a resistance adder of 0.3mOhm.
Figure 11
Drain to Source on-state resistance
In addition to the table, the data sheet contains a diagram of the on-state resistance as a function of the junction
temperature. The higher the junction temperature, the higher the RDSon will be. Due to this positive temperature
coefficient, it is easy to switch several devices in parallel.
The diagram is shown for typical RDSon values only.
Figure 12
Typical drain-source on-state resistance RDS(on)=f(Tj)
To calculate the dependency of the junction temperature following formula has to be taken:
(7)
R DSon (TJ )  RDSon _ 25C  (1 
 TJ  25C
)
100
 is a technology related constant. For an approximation an alpha value of 0.4 can be taken for power
MOSFETs.
Application Note
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Datasheet Parameters
3.9
Gate threshold voltage
The Gate Source threshold voltage defines the required Gate to Source voltage at a defined Drain current.
During production the threshold voltage is measured at room temperature, with V DS = VGS and an area
dependent Drain current in the µA range. The value is specified in the table with min, typ. and max ratings.
Figure 13
Threshold voltage
Due to the fact that the threshold voltage decreases for increasing junction temperatures this dependency is
specified for typical values in a diagram.
For high junction temperatures, the Drain current can already reach the leakage current (I DSS) of the MOSFET,
therefore an additional curve with ten times higher Drain currents compared to the table specification is defined.
Figure 14
Typical gate threshold voltage VGS(th)=f(Tj)
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Datasheet Parameters
3.10
Capacitances
The capacitances of the MOSFETs are defined on the one hand in the table section of the data sheet but as
well as a diagram due to their dependencies of the Drain to Source voltage.
These parameters are not tested during production, the max values are derived from production variants, which
were investigated during the development of the device in detail.
Because it is not possible to measure some capacitances directly, the Gate to Source etc. capacitances can be
calculated out of the defined values accordingly.
C iss  C GS  C GD
(8)
C oss  C DS  C GD
C rss  C GD
Figure 15
Dynamic characteristics: capacitances
In the diagram area of the data sheet the typical capacitances as a function of the Drain to Source voltage are
defined. Especially the reverse (Crss) and output (Coss) capacitances are showing extreme dependencies over
the voltage. Reason for that is the change in the space charge region during the switching transition of the
MOSFET.
Figure 16
Capacitance C=f(VDS)
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Datasheet Parameters
3.11
Reverse diode characteristics
The characteristics of the MOSFET’s internal diode are given twofold. First in the table part, as in Figure 17,
second as a diagram (Figure 19) with the typical forward diode characteristics I F = f(VSD) at two different junction
temperatures: TJ = 25C and TJ = 175C.

Diode continuous forward current: The maximum permissible DC forward current of the inverse diode at
the specified case temperature TC = 25C (normally equal to the MOSFET’s continuous current).

Diode pulse current: The maximum permissible pulsed forward current of the inverse diode at the
specified case temperature TC = 25C (normally equal to the MOSFET’s pulse current).

Diode forward voltage: A voltage at diode on-state (MOSFET off-state) across the source and the drain
terminals at given diode forward current IF, given voltage VGS = 0V and given junction temperature
TJ = 25C.

Reverse recovery time: The time needed for the reverse recovery charge to recombine. The graphical
explanation of trr is given in Figure 18.

Reverse recovery charge: The charge stored in the diode during its on-time and being absorbed by
another switching device (e.g. MOSFET in the same leg in a bridge configuration). The graphical
explanation of trr is given in Figure 18.
.
Figure 17
Diode characteristics
Figure 18
Explanation of Qrr and trr
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Datasheet Parameters
Figure 19
Typical forward diode characteristics IF=f(VSD)
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Datasheet Parameters
3.12
Avalanche characteristics
The dependence of the pulsed avalanche current IAV on the time in avalanche tAV is presented in Figure 20.
Operation of the MOSFET below the curve, under consideration of the maximum junction temperature in pulsed
avalanche, is allowed. For the same avalanche energy, if the current decreases, the time in avalanche would
increase. Additional parameter in the figure is the junction temperature at the beginning of the avalanche event.
The increase of temperature leads to decrease of the avalanche capability.
Figure 20
Avalanche characteristics IAS=f(tAV)
3.13
Avalanche energy
The table part of the datasheet gives information on the maximum avalanche energy at given avalanche current,
as well as the maximum current in avalanche.
Figure 21
Avalanche energy and current
The diagram in Figure 22 shows the variation of the maximum single-pulse avalanche energy E AS as a function
of chip temperature at a given avalanche current. With increasing junction temperature the avalanche power
handling capability decreases according to:
2
(9)
 TJ _ max  TJ 
 E
E AS (TJ )  
o
AS _ 25o C
T


25
C
J
_
max


This formula is valid for the specified avalanche current only. By varying the avalanche current, the diagram
would show different results. As a rule of thumb the avalanche power handling capability is inversely
proportional to the avalanche current.
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Datasheet Parameters
Figure 22
Avalanche energy EAS=f(Tj)
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Datasheet Parameters
3.14
Drain-source breakdown voltage
The diagram in Figure 23 gives the typical dependency of the minimum value of the drain to source breakdown
voltage over the whole temperature range (-55C…+175C). The table value, as given in Figure 24 gives the
min value of the breakdown voltage at 25C.
Figure 23
Drain-source breakdown voltage VBR(DSS)=f(Tj)
Figure 24
Drain-source breakdown voltage VBR(DSS) @ 25°C
Application Note
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Datasheet Parameters
3.15
Typical gate charge
The diagram shows the typical variation of the requisite gate charge at the given gate source voltage and drainsource supply voltage for switching on a power MOSFET. The on state current is given as a parameter.
The gate charge comprises the charge QGS, which is required for charging the gate-source capacitance CGS.
During this phase, after the gate threshold voltage VGS(th) has been reached, the drain current rises to its
specified value, and the drain source voltage then falls (it can happen simultaneously for the resistive loads or
after one another with the inductive loads). Until the voltage VDS has fallen to its actual on-state value
(VDS = RDSonID), the gate-to-drain capacitance (Miller capacitance) has to be discharged. This charge
component is defined as the gate-to-drain charge QGD. The charge QGS + QGD is not sufficient to fully switch the
transistor on, since the drain-source on-state resistance has not yet been minimized. Only with a charge
corresponding to a full gate source voltage is the full turn-on resistance reached, and thus static losses,
optimized. This whole charge QG depends on the drain-source voltage (or the supply voltage) that has to be
switched. The charge values are also summarized in the table part as shown in Figure 26.
Figure 25
Typical gate charge VGS = f(Qgate) and gate charge waveforms
Figure 26
Gate charge and plateau voltage
Application Note
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Datasheet Parameters
3.16
Leakage Currents
There are two leakage currents specified for a MOSFET:
IDSS is the drain-source leakage current at a certain drain-source voltage (typically the minimum drain-source
breakdown voltage) and at VGS=0V.
IGSS is the gate-source leakage current at a certain gate-source voltage (typically the max. gate-source voltage)
and at VDS=0V.
Figure 27
Leakage Currents
3.17
Switching Times
The turn-on time, ton, of a MOSFET is the sum of the turn-on delay time td(on) and the rise time tr. td(on) is
measured between the 10% value of the gate-source voltage and the 90% value of the drain-source voltage.
The rise time tr is measured between the 90% value and the 10% value of the drain-source voltage.
The turn-off time, toff, of a MOSFET is the sum of the turn-off delay time td(off) and the fall time tf. td(off) is
measured between the 90% value of the gate-source voltage and the 10% value of the drain-source voltage.
The fall time tf is measured between the 10% value and the 90% value of the drain-source voltage.
Figure 28
Definition of switching times
Figure 29
Switching Times
Application Note
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