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Bridging Theory in PracticeTransferring Technical Knowledgeto Practical Applications
Protected High Side Drivers
Protected High Side DriversOvervoltage
ProtectionPower Stage
TemperatureSensor
CurrentControl
ChargePump
OvervoltageLogic
ESDProtection
OvervoltageProtection
Logic
Power OutputStage
Intended Audience:• Electrical engineers with a knowledge of simple electrical circuits• An understanding of MOSFETs and high side drivers is assumed
Topics Covered:• What is a PROFET?• What type of protection does a PROFET have?• What type of diagnostics does a PROFET have?• How does a PROFET impact system EMI?• How is a PROFET circuit implemented?• PROFET Selection Questions
Expected Time: • Approximately 90 Minutes
Protected High Side Drivers
Protected High Side Drivers
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
D
S
G
N-ChannelMOSFET
( Enhancement) (
MOSFET Metal Oxide Semiconductor Field Effect Transistor
VGS
VSG
n+
p+
n+
p+
n+
n-
GateSource Source
Drain
P-ChannelMOSFET
(Enhancement)
MOSFET Review
G
D
S
GS
D
MOSFETRegions of Operation
• A positive (for N-Channel) or negative (for P-Channel) VGS produces a conducting channel between the Drain and Source
• The MOSFET is then able to operate in two regions:– 1) Linear region: The MOSFET behaves like a resistance.– 2) Saturation region: The MOSFET behaves like a current source.
VGS > 0V
N-ChannelMOSFET(NMOS)
IDS
VDS
VG
S i
ncr
ease
s
VDS = VGS-VT
High Side Drive (HSD) Configuration
14V
Load
MOSFETSwitch
The switch is on the “HIGH”side of the load
To turn on the HSD, the MOSFETgate is pulled high
14V
But, the maximum voltage at theMOSFET source is VG - VT
VS ~ 13V
The low value of VGS translatesinto a small ILOAD (saturation region)
ILOAD
VGS ~ 1V
High Side Drive (HSD)Configuration
14V
Load
MOSFETSwitch
The switch is on the “HIGH”side of the load
To turn on the HSD, the MOSFETgate is pulled high
26V
The source voltage is now approximately Vsupply
VS ~ 14V
If the MOSFET gate is pulled toa higher voltage…
The high value of VGS translatesinto a large value of ILOAD
(linear region)
ILOAD
VGS ~ 14V
PROFETs = PROtected FETs
PROFET
MOSFETDiagnostics
Short CircuitProtection
IntegratedCharge Pump
OverVoltage
Protection
Current Limit
OverTemperature
Protection
ReverseBattery
Protection
Voltage Controlled PROFET Block DiagramVoltage Controlled
IN
Current Controlled PROFET Block DiagramCurrent Controlled
IN
IIN
Current Controlled PROFET Block DiagramCurrent Controlled
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
Rugged vs. ProtectedRugged
• MOSFETs• Achieved through
process & manufacturing technology
• Protection Not Built in
Protected • PROFETs• Achieved through design and
utilization of more advanced integrated circuit technologies
• Available CMOS, DMOS and Bipolar devices allow for the integration of ESD protection, active clamping, current limit, temperature sensing, etc.
• Protection Built in
Protected • PROFETs• Achieved through design and
utilization of more advanced integrated circuit technologies
• Available CMOS, DMOS and Bipolar devices allow for the integration of ESD protection, active clamping, current limit, temperature sensing, etc.
• Protection Built in
Protected • PROFETs• Achieved through design and
utilization of more advanced integrated circuit technologies
• Available CMOS, DMOS and Bipolar devices allow for the integration of ESD protection, active clamping, current limit, temperature sensing, etc.
• Protection Built in
PROtected FET (PROFET)Protection Features• Electrostatic Discharge (ESD) Protection• Overvoltage / Load Dump Protection• Overvoltage Shutdown Protection and Restart• Undervoltage Shutdown Protection and Restart• Reverse Battery Protection• Reversave™ Battery Protection• Inductive and Overvoltage Output Clamp Protection• Thermal Shutdown Protection• Current Limit Protection• Short Circuit Shutdown Protection• Inversave™ Inverse Current Protection• Loss of Ground Protection• Loss of Supply Voltage Protection
Block Diagram Including Protection Features
ESD Protection
Overvoltage Protection
VAZ
Overvoltage Shutdown Protection and Restart
Undervoltage Shutdown Protection and Restart
Load Dump Protection
• The rated load dump voltage is a function of the generator impedance (RG) and the load resistance (RL)
• As RG and RL increase, less energy is dissipated in the PROFET, and the maximum allowable load dump voltage increases
4) The over temperature protection is not active during reverse current operation!
The PROFET will requires a 150 resistor in the GND connection to limit the reverse supply current.
Reverse Battery Protection
4) The temperature protection is not active during reverse current operation!
Reverse Battery Protection
The reverse load current through the intrinsic drain- source diode has to be limited by the connected load. Power dissipation is higher compared to normal operating conditions due to the voltage drop across the drain-source diode.
4) The temperature protection is not active during reverse current operation!
Reverse Battery Protection
PROFETs with ReverSaveTM
protection overcome thisproblem…
Rbb
ReverSave™ Reverse Battery Protection
In PROFETs with ReverSaveTM protection, the MOSFET is turned on by the voltage drop across the resistor Rbb.
With the MOSFET conductingthe reverse load current (instead of the intrinsic diode), the power dissipation is greatly reduced under reverse batteryconditions.
Inductive and Overvoltage Output Clamp Protection
Thermal Shutdown Protection
A B C D E
InputVoltage
LoadCurrent
JunctionTemperature
F
Current Limit Protection
IL(SCr)
IL(SCp)
Short CircuitShutdown Protection
VON(SC)
Short CircuitShutdown Protection
Inversave™ Inverse Current Protection
Devices with Inversave™ can be operatedin inverse current mode.
When the device is off, only the intrinsic diode conducts with high power dissipation.
When device on, MOSFET turns on forlower power dissipation.
Loss of Ground Protection• With Loss of Ground Protection, Vbb, VIN, and VST are still
referenced to ground through the output• This ensures the device will be safely shut off if the ground pin
is opened
Loss of Supply Voltage Protection• All PROFETs are protected against a loss of supply voltage for
non-inductive loads• Most PROFETs are also protected against a loss of supply
voltage for inductive loads by handling the recirculation current through the GND pin
I
VOUT goes negative
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
PROFET Diagnostic Feedback Digital vs. Analog
ISTATUS
GND
STATUS
Digital Diagnostic Feedback• The type of fault is determined by a diagnostic truth table
Normal Operation
Short Circuit to GND
Short Circuit to Vbb
Overcurrent
Overtemperature
Open Load
Input
L
H
L
H
L
H
L
H
L
H
LH
Output
L
H
L
L
H
H
L
H
L
L
HH
Status
L
L
L
H
H
L
L
L
L
H
HL
14V
Load
PROFET
Input
StatusOutput
Analog Diagnostic Feedback• The type of fault is determined by a diagnostic truth
table AND a sense ratio parameter14V
Load
PROFET
Input
IIS
OutputRIS
Normal
Operation
Overcurrent
Short Circuit
to Ground
Overtemperature
Short Circuit
to Vbb
Open Load
Input
Current
L
H
L
H
L
H
L
H
L
H
L
H
Output
Voltage
L
H
L
H
L
L
L
L
H
H
Z
H
Current
IIS
IIS(LL)
nominal
IIS(LL)
IIS,FAULT
IIS(LL)
IIS,FAULT
IIS(LL)
IIS,FAULT
IIS(LL)
< nominal
IIS(LL)
IIS(LH)
Analog Load Current FeedbackVia IIS Current
• Under normal operation, IIS is proportional to the output current
• KILIS = IL / IIS ~ 10,000
• For example:IL = 25A
IIS ~ 2.5mA
IIS Current Sense Ratio• The accuracy of IIS improves with increasing output current
KILIS
(IL / IIS)
IIS Current Sense Ratio
• The accuracy of IIS improves with increasing output current
Less Accurate
More Accurate
Status Signal Settling Time
• The Status signal is not valid during a settling time after turn-on, turn-off, or after change of load current
• This is true of PROFETs with analog or digital diagnostic feedback
Open Load DetectionThree Different PROFET strategies
• Open load detection via Sense pin on HiC (High Current) PROFETs and some PROFETs
• Open load detection while PROFET is turned on (for some PROFETS---mostly older types)
• Open load detection while PROFET is turned off (for most PROFETs---mainly newer types)
Open Load Detection – Via Sense Pin
Under an open load condition,the PROFET will maintain IIS below 1A (maximum).
CurrentSense
Open Load Detection – PROFET On
An open load is detected if the PROFET is on and the voltage across the MOSFET is
VON < RdsonIL(OL)
Open Load Detection - PROFET Off
Using an external resistor, an open load is identified if the PROFET is turned off and VOUT > 3.2V (typ.)
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
MOSFET High Side Drive
• Recall, the gate of the N-Channel MOSFET must be at a voltage higher than the transistor’s source to turn the MOSFET on:
• With VSUPPLY being the highest voltage in the system, where does VGATE come from?
14V
Load
MOSFETSwitch
26V
VS ~ 14V
ILOAD
VGS ~ 12V
Charge Pump Gate Voltage• A charge pump is used to raise (pump) the gate
voltage to an acceptable level to turn on the MOSFET
Switch B
Switch A
DADB
CACB
VSUPPLY
VOUT
Charge Pump Gate Voltage
• Initially, Switch A is closed, and CA is charged to VSUPPLY - VDA
Switch B
Switch A
DADB
CACB
VOUT
VSUPPLY = 14V
~13V
Charge Pump Gate Voltage
• Next, Switch B is closed, and current flows from CA, through DB to charge CB
Switch B
Switch A
DADB
CACB
VOUT
VSUPPLY = 14V
~13V
Charge Pump Gate Voltage
• But, CA acts like a battery in series with VSUPPLY
Switch B
Switch A
DADB
CACB
VOUT
ReverseBiased
VSUPPLY = 14V
~13V
~27V
~26V
• Now, the High Side Drive MOSFET can be turned on
• The turning on and off of Switch A and Switch B, however, leads to a new problem….
MOSFET High Side Drive
14V
Load
MOSFETSwitch
26V
VS ~ 14V
ILOAD
VGS ~ 12V
Charge Pump Electromagnetic Interference (EMI)
Frequency (MHz)
0
20
40
60
80
100
120
0.1 1 10 100 1000
LW
M
KW
UKW
dBV
0
20
40
60
80
100
120
1.0 10 1000.1
Charge pumpscan cause harmonic
emissions
0
20
40
60
80
100
120
LW
MW
KW
UKW
Frequency (MHz)
dBV
0
20
40
60
80
100
120
1.0 10 1000.1
Newer, improved design reduces emissions
20 - 30 dB
PROFET’s Improved Charge Pump Reduces (EMI)
0
20
40
60
80
100
120
0.1 1 10 100 1000
Frequency [MHz]
dBµV
BTS 736 L2ESG1
ESG2ESG3ESG4
ESG5 (DB)BMW
LW
M
KW
UKW
0
20
40
60
80
100
120
0.1 1 10 100 1000
Frequency [MHz]
dBµV
BTS 736 L2
ESG1ESG2ESG3ESG4
ESG5 (DB)BMW
LW
M
KW
UKW
Filter solutions may be required for the charge pump
Vbb
IN
OUT
GND150
GND
load
BTS736
CEMI
Vbb
IN
OUT
GND
load
BTS736
CEMI
Filtering - RC 150/4.7nF Filtering - C= 2µF
Continuous charge pump emissionContinuous charge pump emission
EMI/EMC Emissions due to PWM Operation• One source of EMI/EMC emissions is the internal charge pump as
shown on previous slides
• The other source of emissions can be PWM operation
• During PWM operation the slew rate and shape of the output voltage and current waveforms cause an increase in the emission spectra
• For slow switching applications (most Profets used at 100Hz) this results in an increase of the emission spectra below approximately 1Mhz.
Benefits of Edge Shaping• Edge shaping allows to reduce emission levels while maintaining a
slew rate which still allows for permissible power loss levels
Slew rate
control
Slew control only
Theoretical ideal
100%
90%
10%
0%
Edge shaping
Edge shaping
Turn off edge shaping
Hi-Current Profet---EMC improvements• BTS650-Original Hi-current design with slew rate control only.• BTS6510-Same as BTS650 with longer switching times• BTS443P-Second generation with edge shaping for current turn off• BTS6143/44-Third generation with edge shaping for current turn on and offOperating point: Vs=13.5V, ILoad =5A, fs = 100Hz, resistive load
Emission Spectra:
Ten
denc
y
0
10
20
30
40
50
60
70
80
90
100
110
120
0.1 1 10 100 1000
f / MHz
dB
µV
BTS650
BTS6510
BTS443
BTS6144P
Noise
Class 1 P
Class 2 P
Class 3 P
Class 4 P
Class 5 P
BMW
Device: BTS650 / BTS6510 / . BTS443 / BTS6144P0 / . BTS6144PLoad: 60W BulbO-Mode: PWM 100HzDetector: Peak
BTS 650 vs. BTS6510 vs. BTS 443 vs. BTS6144
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
Overvoltage Protection of Logic Functional Block
• RGND required to limit current through DAZ
• RST required to protect microcontroller input pin
• RIN may be required to protect microcontroller output pin
RST
RINVAZ
RGND
Reverse Battery Protection• RGND required to limit current through logic zener diode
• RST required to protect microcontroller input pin
• RIN may be required to protect microcontroller output pin
• RL must limit current through power inverse diode
RST
RGND
RIN
RL
Reverse battery—Power Dissipation• Power dissipation during reverse battery can be higher than
normal operation due to conduction of load current through the FET body diode
• For example:– 3A load with 100mohm Fet in normal mode gives 0.9W– 3A load thru body diode in reverse battery gives 2.1W (3A*0.7V)
• The discrepancy between normal mode dissipation and reverse battery dissipation becomes worse as load current becomes higher
• Care must be take to control this dissipation to safe levels since over temperature protection is not active during reverse battery.
• This leads us to a feature where the MOSFET channel can be turned on during reverse battery operation---ReverSave
ReverSave™ Reverse Battery Protection Circuitry
• About 100mA of current must flow through the Rbb (from the IN or STATUS pins) to turn on the MOSFET in inverse mode
• Currents above 100mA in Rbb may create excessive power dissipation. Add RIN to limit
current below 100mA
IS Pin Overvoltage Protection• Overvoltage conditions greater than 67V (typ) can cause the IS pin to
exceed 5V - damaging a microcontroller input pin• The IS pin can be clamped by an external diode if necessary
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
PROFET Selection: Customer Questions
• How many channels?• What is the load current?• Is the load capacitive and what is the inrush current?• Is the load inductive and the inductance and/or energy during turn-off?• Will load be on/off or PWM? What is PWM frequency?• What is ambient temperature?• What type of package - surface mount or through-hole?• If surface mount, how much copper area for Vbb / tab connection?
• If through-hole, what type of heatsink will be provided for package?• What diagnostics are needed?• What application extremes will the device / system be subjected to
(reverse battery, load dump, overvoltage etc.)?
What Is the Load Current?• What is the maximum load current?• When does the maximum occur?• What is the typical load current?
• Alternative Question: What is the load resistance?
• Alternative Question: If the load is a lamp, what is it’s wattage?
• Recall, the load current is fundamental in determining an appropriate PROFET Rdson value
500mA
5.5A
Is the Load Capacitive?What Is the In-rush Current?
• Recall, the in rush current for lamps and RC networks may be an order of magnitude higher than the steady state current
What Is Load Inductance or Energy During Turn-Off?
• FETs are rated for the max absorbable energy when turning off inductive loads
Will the Load Be On/Off or PWM? What is PWM frequency?
• PROFETs are often used in applications where the load is pulse width modulated – especially lighting applications
PWM Definitions• Frequency-(frequency domain) What is the rate of repetition of
a waveform?• Duty cycle-(Time domain) What is the amount of time spent on
with respect to the amount of time spent off?
T0 T1 T2 T3 T4
I0
I1
Period
Ton Toff
Frequency= 1/Period
Duty Cycle = Ton/(Ton+Toff)
Period = Ton + Toff
What Is the Ambient Temperature?• Minimum ambient temperatures is usually -40C
• Maximum ambient temperature ranges from 85C to 125C for most applications:
85C for most non-powertrain applications105C for some in-dashboard applications125C for most powertrain applications
What Type of Package?Surface Mount or Through-hole?• Many applications require all surface mount
components
• Surface mount components typically only have excess copper board space heatsinks
• Through-hole components can have large heatsinks for improved power dissipation
If Surface Mount - How Much Board Area Is Available for Heatsinks?
• Engineers must trade-off the cost and size of the heatsink vs. the Rdson (and hence, the cost) of the PROFET
Introduction to PROFETs
• Introduction to PROFETs
• PROFET Protection Features
• PROFET Diagnostic Features
• EMI/EMC Considerations
• System Implementation
• Frequently Asked Questions
Introduction to PROFETsOvervoltage
ProtectionPower Stage
TemperatureSensor
CurrentControl
ChargePump
OvervoltageLogic
ESDProtection
OvervoltageProtection
Logic
Power OutputStage
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