A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Philips Research University of Twente, Faculty of Electrical Engineering

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Contents Introduction Circuit fundamentals Design strategy Implementation Specifications Conclusions Introduction Circuit fundamentals Design strategy Implementation Specifications Conclusions

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Introduction –enable thermal protection (shutdown,clock frequency lowering etc.) –use in integrated measurement or control devices Why need integrated CMOS temperature indicator?

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Introduction –Thermal protection only requires threshold temperature detection (125 °C) –Multiple threshold values together form a digital temperature indicator Why design switch and not a linear temperature dependent output?

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Design goals Standard 0.18  m CMOS process Low voltage, Low power, Small area High accuracy Portable Switch temperature of 125 °C Extendable:  adjustable switch temperature  multiple switch temperatures  high accuracy over large T range

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Circuit Fundamentals Use bandgap principle: V T V be V T V gap,0 V T V ptat

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Circuit Fundamentals Detect crossing of V ptat with V be V T V ptat V T V be

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Design strategy –Bipolar transistor V be spread –Resistor matching & spread –Offset and noise of MOST devices Establish quantitative relation for optimal MOST area distribution Identify accuracy limitations:

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Design strategy

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Design strategy Assume: Find equivalent offset (or flicker noise): Minimal  total given fixed Area total when:

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Implementation –High amplifier gain; speed may be low. –High supply and substrate noise rejection. Implementation limitations: –Low supply voltage  cascoding difficult. –Folded cascodes not desirable Implementation goals:

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Implementation

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Implementation Positive feedback; high gain, small bandwidth

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Implementation –Robust circuit, easy to port –Small flicker noise & offset  straightforward use of large transistors instead of using complex dynamic offset cancellation techniques. –No cascoding or shielding  low supply voltage –All matched transistors have matched conditions at threshold temperature Strong points:

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Implementation Weak point: –Nested inner loop  stability analysis not straightforward

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Chip photograph Transconductance amplifier Comparator Resistors Diode connected BJTs 150  m 190  m

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Specifications

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Conclusions Efficient & Robust Design strategy Very low power circuit –can decrease further with duty-cycle mode Good performance without calibration –3  intra-batch deviation of only 1.1  C Design is well-suited for multiple thresholds extension

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Philips Research University of Twente, Faculty of Electrical Engineering

A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl A 1-V 15  W High-Precision Temperature Switch D. Schinkel, R.P. de Boer, A.J. Annema and A.J.M. van Tuijl Philips Research University of Twente, Faculty of Electrical Engineering