Presented by: David Divins at - Infineon Technologies · David Divins Senior Staff Field ... 10.05...
Transcript of Presented by: David Divins at - Infineon Technologies · David Divins Senior Staff Field ... 10.05...
October 2007 1
Presented by:David Divins
at
October 2007 2
Using Simulation to Estimate MOSFET Junction Temperature in
a Circuit Application
Presented by:David Divins
Senior Staff Field Applications EngineerInternational Rectifier
October 2007 3
Agenda
Definition of Electro-Thermal SimulationSimulation Tools and MethodsMethods of Estimating Die TemperatureCreating Quasi-Dynamic MOSFET ModelModel GenerationExample ApplicationConclusion
October 2007 4
Electro-Thermal Simulation
Purpose of Electro-Thermal Simulation is to predict MOSFET junction for a given application.
DiePackage
FR4 Board Solder joint
Heatsink
October 2007 5
Electro-Thermal Simulation
ApplicationsSolenoid driversMotor driveLighting ballastDC/DC convertersSwitch model power suppliesClass D amplifiers
October 2007 6
Simulation Tools and Methods
ToolsSimplorer (Ansoft) - Circuit/System simulator with VHDL-AMS hardware description languageSaber (Synopsis) - Circuit/System simulator with VHDL-AMS and MAST hardware description languagesSpector (Cadence) - Circuit/System simulator with Verilog-A hardware description languagePSPICE (Cadence) – Defacto standard in circuit simulation.
October 2007 7
Simulation Tools and MethodsMethod
Implementing model in the hardware description languageImplementing model using equations and macro modeling
library ieee; use ieee.std_logic_1164.all;use ieee.electrical_systems.all;
entity comparator isport ( terminal a : electrical;
signal d : out std_ulogic );end entity comparator;
----------------------------------------------------------------
architecture ideal of comparator isconstant ref_voltage : real := 5.0;quantity vin across a;
begin
comparator_behavior : process isbeginif vin > ref_voltage / 2.0 thend <= '1' after 5 ns;
elsed <= '0' after 5 ns;
end if;wait on vin'above(ref_voltage / 2.0);
end process comparator_behavior;
end architecture ideal;
Source Drain
Gate
ΘH RTH1
117.73m K/W
CTH1
211.98u Ws/KCTH2
1.38m Ws/KRTH2
601.26m K/W
CTH3
32.33m Ws/K
RTH32.01 K/W
T1 Ta aCH1
+ V
Vds
A
Iddr
Abs
FCT_ABS1
PWRProbe
PWR
EQU
Equations
10
Ta
10
Tj
+ V
Vdst
10
Rdson
10
dr
10
PWR
irfr9024
+ V
Vgs
October 2007 8
Simulation Tools and Methods
Quasi-Dynamic MOSFET model implementationMacro modeling with use of linking equationsUsing a multi domain simulator that allows for Electro-Thermal simulation.• Volts and Amps• Heat flow (Watts) and temperature
Thermometer
H
Heat
+ V
Voltmeter
A
Ammeter
October 2007 9
Methods of Estimating Die Temperature
Methods of estimating MOSFET die junction temperatureEquation based + Thermal Impedance curve
DVIP ∗∗=
Where:I = average current during the conduction cycleV = equivalent voltage across the device during the conduction cycleD = duty cycle
October 2007 10
Methods of Estimating Die Temperature
Use Power calculated with P=I*V*DUse pulse width and duty cycle to determine Zth (thermal impedance) from device thermal impedance curve Temperature rise (ΔTjunction)= Zth * P
October 2007 11
Methods of Estimating Die Temperature
Limitations of the equation based junction temperature estimate
Only temperature rise from junction to case is taken into account. Neglects case to ambient temperature rise.Assumes the power pulse is an ideal square edged pulse train.It does not allow for transient thermal response.
Junction
Case
Ambient
TemperatureRise Calculated
Case to Ambient Temperature Rise Not calculated
October 2007 12
Methods of Estimating Die Temperature
Simulator based MOSFET junction temperature estimateUses circuit simulation to calculate junction temperature in an applicationThe circuit can be arbitraryTransient thermal response is calculatedComponent parameters change with temperature
IRF2804S_7P_Therm
IRF2804S_7P_Therm
IRF2804S_7P_ThermIRF2804S_7P_Therm1
I1
Rdrv
Bus
C1
R2R1
Vbus V
STATE1
TRANS1
STATE2
C
25.00
150.00
50.00
100.00
0 72.28m25.00m 50.00m
FET Junction Temperature
IRF28...
1.50u
27.80
10.00
0 200.00m
Load Voltage
N0009.V
A
-20.00n
182.47
100.00
0 4.35m2.00m
Load Current
Bus.I [A]
+ V
Vgs
-50.00m
10.05
5.00
0 200.00m
Gate Voltage
Vgs.V ..
A
AM1
D1
ICA:
Parameters
Parameters
Name Valuetrig 1.00mIpk 200.00Iss 40.00
Vbus 28.00R1 175.00mR2 700.00mIg 100.00u
W
0
1.50k
500.00
1.00k
0 4.00m2.00m
FET Power
IRF28...
+ V Vsw
TRProbe
Tj
TRProbe
Load_current
Measured Values
Name ValueBus.I [A] 42.76
Load_current.MAX 186.82Temp_Rise 148.25
EQU
Equations
C
60.00
366.25
200.00
300.00
10.00u 1.00m30.00u 100.00u200.00uA
FET Junction Temp Rise vs. Gate Current
Tj.MAX
C
25.00
368.00
100.00
200.00
300.00
0 200.00m100.00m
Tj
A
-20.00n
192.00
100.00
0 200.00m100.00m
Load Current
A
167.65
191.80
180.00
8.00u 1.00m500.00uA
Peak Load Current vs Gate Drive Current
Load_...
Experiment Table
RunNo Ig Load_current.MAX Tj.MAX1.002.003.004.005.006.007.008.009.00
10.00
10.00u16.68u27.83u46.42u77.43u129.16u215.44u359.38u599.48u1.00m
167.68174.47179.20182.85185.65187.68189.41190.50191.25191.71
366.02314.35271.71207.12156.68116.8983.1163.1760.7560.25
Driver
(C)
0
150.00
0 200.00m
Peak Tj for IRF2804_7P
Tj.MAX -39.20m
10.05
5.00
0 200.00m100.00m
Gate Voltage vs. Ig
Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V .. Vgs.V ..
+ V Vds1
+ V
Vds2
(V)
0
30.6020.00
0 200.00m
Vds1
Vds2....(V
)
-2.44
1.400
0 200.00m
Vds2
Vds1....
October 2007 13
Methods of Estimating Die Temperature
Assumptions made for junction temperature estimates using simulation
No other source of heat considered (Temperature rise due to self heating only)Only MOSFET RDS(on) and threshold voltage changes with temperatureSince simulation solves Ordinary Differential the junction is assumed to be a point source of heat.
October 2007 14
Creating Quasi-Dynamic Thermal MOSFET Model
Gathering information:25C Spice Model of MOSFETDatasheet information• RDS(on) vs. Temperature curve• Thermal Impedance Curve
with thermal RC ladder network
.SUBCKT irf1404 1 2 3 * SPICE3 MODEL WITH THERMAL RC NETWORK ************************************** * Model Generated by MODPEX * *Copyright(c) Symmetry Design Systems* * All Rights Reserved * * UNPUBLISHED LICENSED SOFTWARE * * Contains Proprietary Information * * Which is The Property of * * SYMMETRY OR ITS LICENSORS * *Commercial Use or Resale Restricted * * by Symmetry License Agreement * ************************************** * Model generated on April 2, 01 * MODEL FORMAT: SPICE3 * Symmetry POWER MOS Model (Version 1.0) * External Node Designations * Node 1 -> Drain * Node 2 -> Gate * Node 3 -> Source M1 9 7 8 8 MM L=100u W=100u .MODEL MM NMOS LEVEL=1 IS=1e-32 +VTO=3.74133 LAMBDA=0.00250986 KP=514.947 +CGSO=7.17952e-05 CGDO=1.60578e-08 RS 8 3 0.00282867 D1 3 1 MD .MODEL MD D IS=1.89845e-10 RS=0.00218742 N=1.20398 BV=40 +IBV=0.00025 EG=1.2 XTI=1.85712 TT=2.00014e-05 +CJO=5.42237e-09 VJ=2.67939 M=0.566441 FC=0.1 RDS 3 1 1e+06 RD 9 1 0.000681391 RG 2 7 3.16781 D2 4 5 MD1 * Default values used in MD1: * RS=0 EG=1.11 XTI=3.0 TT=0 * BV=infinite IBV=1mA .MODEL MD1 D IS=1e-32 N=50 +CJO=3.13813e-09 VJ=0.970446 M=0.823421 FC=1e-08 D3 0 5 MD2 * Default values used in MD2: * EG=1.11 XTI=3.0 TT=0 CJO=0 * BV=infinite IBV=1mA .MODEL MD2 D IS=1e-10 N=0.4 RS=3e-06 RL 5 10 1 FI2 7 9 VFI2 -1 VFI2 4 0 0 EV16 10 0 9 7 1 CAP 11 10 7.84089e-09 FI1 7 9 VFI1 -1 VFI1 11 6 0 RCAP 6 10 1 D4 0 6 MD3 * Default values used in MD3: * EG=1.11 XTI=3.0 TT=0 CJO=0 * RS=0 BV=infinite IBV=1mA .MODEL MD3 D
IS=1e-10 N=0.4 .ENDS irf1404
October 2007 15
Creating Quasi-Dynamic Thermal MOSFET Model
25C Spice ModelCharacterized to the datasheetDoes not change performance characteristics as power is calculatedUsed as base model for Quasi-Dynamic MOSFET model
October 2007 16
Creating Quasi-Dynamic Thermal MOSFET Model
MOSFETModel in
Simulation
ThermalNetwork
Power Calculation
Temperature (Tj)
Rdson=F(Tj)
Vth=F(Tj)
October 2007 17
Model Generation
Ladder NetworkA thermal RC network used to model the dynamic thermal behavior of the package + mounting system.
Package + MountingEquivalent RC Ladder Network
ΘH RTH1
117.73m K/W
CTH1
211.98u Ws/KCTH2
1.38m Ws/KRTH2
CTH3
32.33m Ws/K
RTH3
T1 Ta aCH1
AbsPWRProbe
The ladder network can be synthesized from the thermal impedance curveor is given by the MOSFET manufacturer
October 2007 18
Model GenerationTying the thermal model to the 25C Spice model
Create the equation that represents RDS(on) vs. temperature
)**2(*)25()( bTjaCRdsondTj
TjdRdson+=
)25(*)**2(*)25( −+= TjbTjaCRdsondRdson This expression gets implemented in the model
Note: a, b and c are calculated via a curve fitting routine. The Rdson vs Temperature curve is assumed to be quadratic.
October 2007 19
Model Generation
Create the voltage source that represents the temperature dependence of Vth (threshold voltage)
)25(*007.0)( −−= TjTjVth Expression used in model.
The voltage source is in series with the MOSFETs gate.
October 2007 20
Model Generation
Calculating the power in the MOSFET for use in the thermal network.
VdsIdP *=
This calculated power is the source for the thermal network.
October 2007 21
Model Generation
Putting it togetherdr
EQU
Equations
+ V
Vds
PWRProbe
PWR
Abs
PWR_abs
RTH1
0.195105 K/W
CTH13.808m Ws/K
CTH226.941m Ws/K
RTH2
305.073m K/W
ΘT1
Ta aC
HH1
Drain
Gate
Source
10Tj
10Ta
10PWR
+ V
Vdstirf2804s7p
irf2804s7p1Vth
dt:=Tj.T-TaTj:=Tj.T-273.15if(Vds.V<0.1) {Rdson25:=abs(Vds.V/dr.I)} else {dr:=1m}if(Vds.V<0.1) {dr:=(7.41u*Tj+3.519m)*dt*Rdson25} else {dr:=1u}PWR:=PWR_abs.VALVth:=-7m*(Tj-25)
Tj
RTH3
October 2007 22
Model GenerationFinal model
25C Spice modelAdded voltage source Vth in gate implements Vth(Tj)dr implements Vds and the current in dr are used to calculate RDS(on) 25CVdst and the current in dr is used to calculate the total powerPWR_abs is used to insure that the thermal network is driven with positive power.
October 2007 23
Example Application
High side switchMOSFET being driven by a opto isolated drive
Very low drive current capability
Load is capacitive Issue: How does driving this load effect the junction temperature of the MOSFET
October 2007 24
Example Application
Simulation Schematic
C2A2 Vop2
Von2
Von1
Vop1A1
C1
PV
I105
0N
PVI1050N
R1Vcc24 V
S1
STATE1
TRANS1
STATE2
C1400u F
Vbus
108 V
R210 Ohm
1k Ohm
W +
PWR_FET
+ V
Vgs
A
IgCase
IRFP4232_Therm
IRFP4232
N0052
Heatsink
October 2007 25
Example Application
AssumptionsTambient=25CHeak sink is modeled as just a thermal resistorC1 & R2 represent a load system i.e. power supplyIg, Vgs, PWR_FET, States 1 & 2, Trans1 and S1 are measurements, input stimulus and ideal switch
October 2007 26
Example Application
Results
Gate Voltage, Junction Temperature, Power and Current
MOSFET Current(A)
15
0
5
10
MOSFET Power(W)]
1k
0
500
Gate Voltage(V)
15
0
5
10
Junction Temperature(C)
150
0
50
100
t [s] 0 157.50m20.00m 40.00m 60.00m 80.00m 100.00m 120.00m
October 2007 27
ConclusionElectro-Thermal simulation allows for analysis in both electrical and thermal domainsQuasi-Dynamic Thermal MOSFET model allows for self-heating to alter RDS(on) and Vth during simulation as a function of temperatureQuasi-Dynamic Thermal MOSFET Model generation is a data gathering taskThe example shows why it is difficult to switch a capacitive load with an opto-driver and a MOSFET due to the excessive junction temperature spike during turn-on.