Design Article
Comment
DoctorZ
Advanced thermal management materials, which have low coefficients of thermal ...
Bhola_#1
Interesting but there are others that run below -55 C and quite challenging ...
Avionic & military applications need -55°C operation
Steve Knoth, senior product marketing engineer, Linear Technology Corporation
10/20/2010 6:06 AM EDT
Bulletproof protection features
Linear’s LDO family incorporates several protection features that make them ideal for use in both battery-powered and non-portable circuits and systems. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting/shutdown, these ICs also protect against reverse input voltages, reverse output voltages and reverse output-to-input voltages.
Current limit protection and thermal overload protection protect the devices against overload conditions at its output. The addition of foldback keeps the power transistor in its SOA. For example, the LT3070 has SOA protection. The safe area protection decreases current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage up to the absolute maximum voltage rating. Under conditions of maximum ILOAD and maximum VIN-VOUT, the device’s power dissipation peaks at around 3W. If the ambient temperature is high enough, the die junction temperature will exceed the 125°C maximum operating temperature. If this occurs, the LT3070 relies on two additional thermal safety features. At about 145°C, the PWRGD output pulls low providing an early warning of an impending thermal shutdown condition. At 165°C typically, the LT3070’s thermal shutdown engages and the output is shut down until the IC temperature falls below the thermal hysteresis limit. The SOA protection decreases current limit as the IN-to-OUT voltage increases and keeps the power dissipation at safe levels for all values of input-to-output voltage. The LT3070 provides some output current at all values of input-to-output voltage up to the absolute maximum voltage rating. See the Current Limit vs. Temperature curve in Figures 1 & 2.
Figures 1 & 2: LT3070 current limit characteristics
Linear Technology also manufactures a full line of high performance, µModule® voltage regulator devices with design-in simplicity near that of an LDO, in MP and other grades.
See Table 2 below and links.
MP-grade µModule voltage regulators, click here
Full line of µModule voltage regulators, click here.
Next: Conclusion
Linear’s LDO family incorporates several protection features that make them ideal for use in both battery-powered and non-portable circuits and systems. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting/shutdown, these ICs also protect against reverse input voltages, reverse output voltages and reverse output-to-input voltages.
Current limit protection and thermal overload protection protect the devices against overload conditions at its output. The addition of foldback keeps the power transistor in its SOA. For example, the LT3070 has SOA protection. The safe area protection decreases current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage up to the absolute maximum voltage rating. Under conditions of maximum ILOAD and maximum VIN-VOUT, the device’s power dissipation peaks at around 3W. If the ambient temperature is high enough, the die junction temperature will exceed the 125°C maximum operating temperature. If this occurs, the LT3070 relies on two additional thermal safety features. At about 145°C, the PWRGD output pulls low providing an early warning of an impending thermal shutdown condition. At 165°C typically, the LT3070’s thermal shutdown engages and the output is shut down until the IC temperature falls below the thermal hysteresis limit. The SOA protection decreases current limit as the IN-to-OUT voltage increases and keeps the power dissipation at safe levels for all values of input-to-output voltage. The LT3070 provides some output current at all values of input-to-output voltage up to the absolute maximum voltage rating. See the Current Limit vs. Temperature curve in Figures 1 & 2.
Figures 1 & 2: LT3070 current limit characteristics
Summary characteristics of Linear’s MP-grade LDOs
• Quiescent Current – As Low as 3uA
• Up to 80V Input Voltage
• Reverse Protection – Output, Output-to-Input, Input
• Directly Parallelable
• VOUT to 0V
• Low Dropout Voltage: As Low as 90mV Typical
• Ultralow Output Noise: As Low as 20uVRMS
• Fast Transient Response
• Output Current – Up to 5A
• Output Tolerance: Down to ±2% Over Line, Load &Temperature
• Stable with Low-ESR, Ceramic Output Capacitors
• Thermal Limiting
• Current Limit with Foldback Protection
• Variety of Compact, Thermally Enhanced Packages
• Quiescent Current – As Low as 3uA
• Up to 80V Input Voltage
• Reverse Protection – Output, Output-to-Input, Input
• Directly Parallelable
• VOUT to 0V
• Low Dropout Voltage: As Low as 90mV Typical
• Ultralow Output Noise: As Low as 20uVRMS
• Fast Transient Response
• Output Current – Up to 5A
• Output Tolerance: Down to ±2% Over Line, Load &Temperature
• Stable with Low-ESR, Ceramic Output Capacitors
• Thermal Limiting
• Current Limit with Foldback Protection
• Variety of Compact, Thermally Enhanced Packages
Linear Technology also manufactures a full line of high performance, µModule® voltage regulator devices with design-in simplicity near that of an LDO, in MP and other grades.
See Table 2 below and links.
MP-grade µModule voltage regulators, click here
Full line of µModule voltage regulators, click here.
Next: Conclusion
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JMWilliams
10/21/2010 6:14 PM EDT
This was an interesting article.
It would have been more interesting yet, if the author had discussed some more detail on causes and effects of operation of IC's below their rated temperature range.
For example, increased conductance of metals and decreased semiconductor carrier mobility might be factors. What about brittleness of chips and packages because of the cold? I don't know . . ..
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JMWilliams
10/21/2010 6:14 PM EDT
This was an interesting article.
It would have been more interesting yet, if the author had discussed some more detail on causes and effects of operation of IC's below their rated temperature range.
For example, increased conductance of metals and decreased semiconductor carrier mobility might be factors. What about brittleness of chips and packages because of the cold? I don't know . . ..
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BalaLak
10/24/2010 12:54 AM EDT
I agree with the other comment by JMWilliams. The first half of the article is definitely interesting. I'd have liked to see more specific details about effects of low temp (less than -40 degC) operation - in terms of design vs characterization trade-offs, process & material qual challenges.
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mike_lavoie
10/27/2010 10:16 AM EDT
Good Article but a little misleading. the title "Avionic & military applications need -55°C operation" lead me to believe that he would cover all IC's or at least a larger percentage than just LDO's. We deal with -55 & even -60 requirements and it is very challenging so how about some tips on how to make commercial grade work at these temperatures. Screening of components, heaters, holding the circuits in reset until temp rises, better heat sinks and fans for hi temp are a few of the techniques we use. I agree with JW, what are the mechanisms that effect components at these temperatures?
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Bhola_#1
10/30/2010 1:12 AM EDT
Interesting but there are others that run below -55 C and quite challenging performance wise, especially large signal due to different technologies (such as phempt LNA etc.)
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DoctorZ
5/14/2012 2:25 PM EDT
Advanced thermal management materials, which have low coefficients of thermal expansion, can minimize thermal stresses and warping at low temperatures. In addition, they have low densities and thermal conductivities up to 1700 W/m-K. They are well established in aerospace/defense and commercial applications. If anyone wants papers on the subject, send me an email at c.h.zweben@usa.net
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