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TMP442ADCNR Scheda tecnica(PDF) 9 Page - Texas Instruments |
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TMP442ADCNR Scheda tecnica(HTML) 9 Page - Texas Instruments |
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9 / 28 page  BETA COMPENSATION TEMPERATURE MEASUREMENT DATA SERIES RESISTANCE CANCELLATION DIFFERENTIAL INPUT CAPACITANCE TMP441 TMP442 www.ti.com .............................................................................................................................................. SBOS425A – DECEMBER 2008 – REVISED MARCH 2009 Previous generations of remote junction temperature Temperature measurement data are taken over a sensors were operated by controlling the emitter default range of –55°C to +127°C for both local and current of the sensing transistor. However, remote locations. However, measurements from examination of the physics of a transistor shows that –55°C to +150°C can be made both locally and VBE is actually a function of the collector current. If remotely by reconfiguring the TMP441/42 for the beta is independent of the collector current, then VBE extended temperature range, as described in this may be calculated from the emitter current. In earlier section. Temperature data resulting from conversions generations of processors that contained PNP within the default measurement range are transistors connected to these temperature sensors, represented in binary form, as shown in Table 1, controlling the emitter current provided acceptable Standard Binary column. Note that any temperature temperature measurement results. At 90nm process below –64°C results in a data value of –64 (C0h). geometry and below, the beta factor continues to Likewise, temperatures above +127°C result in a decrease and the premise that it is independent of value of 127 (7Fh). The device can be set to measure collector current becomes less certain. over an extended temperature range by changing bit 2 (RANGE) of Configuration Register 1 from low to To manage this increasing temperature measurement high. The change in measurement range and data error, the TMP441/42 control the collector current format from standard binary to extended binary instead of the emitter current. The TMP441/42 occurs at the next temperature conversion. For data automatically detect and choose the correct range captured in the extended temperature range depending on the beta factor of the external configuration, an offset of 64 (40h) is added to the transistor. This auto-ranging is performed at the standard binary value, as shown in the Extended beginning of each temperature conversion in order to Binary column of Table 1. This configuration allows correct for any changes in the beta factor as a result measurement of temperatures as low as –64°C, and of temperature variation. The device can operate a as high as +191°C; however, most PNP transistor with a beta factor as low as 0.1. See temperature-sensing diodes only measure with the the Beta Compensation Configuration Register range of –55°C to +150°C. Additionally, the Section for further information. TMP441/42 are rated only for ambient temperatures ranging from –40°C to +125°C. Parameters in the Absolute Maximum Ratings table must be observed. Series resistance in an application circuit that typically Table 1. Temperature Data Format (Local and results from printed circuit board (PCB) trace Remote Temperature High Bytes) resistance and remote line length (see Figure 12) is automatically cancelled by the TMP441/42, LOCAL/REMOTE TEMPERATURE REGISTER HIGH BYTE VALUE (1°C RESOLUTION) preventing what would otherwise result in a STANDARD BINARY(1) EXTENDED BINARY(2) temperature offset. A total of up to 1k Ω of series line TEMP resistance is cancelled by the TMP441/42 if beta (°C) BINARY HEX BINARY HEX correction is disabled and up to 300 Ω of series line –64 1100 0000 C0 0000 0000 00 resistance is cancelled if beta correction is enabled, –50 1100 1110 CE 0000 1110 0E eliminating the need for additional characterization –25 1110 0111 E7 0010 0111 27 and temperature offset correction. See the two 0 0000 0000 00 0100 0000 40 Remote Temperature Error vs Series Resistance 1 0000 0001 01 0100 0001 41 typical characteristic curves (Figure 7 and Figure 8) 5 0000 0101 05 0100 0101 45 for details on the effect of series resistance on 10 0000 1010 0A 0100 1010 4A sensed remote temperature error. 25 0001 1001 19 0101 1001 59 50 0011 0010 32 0111 0010 72 75 0100 1011 4B 1000 1011 8B The TMP441/42 can tolerate differential input 100 0110 0100 64 1010 0100 A4 capacitance of up to 500pF if beta correction is 125 0111 1101 7D 1011 1101 BD enabled, and 1000pF if beta correction is disabled 127 0111 1111 7F 1011 1111 BF with minimal change in temperature error. The effect 150 0111 1111 7F 1101 0110 D6 of capacitance on sensed remote temperature error is illustrated in Figure 9, Remote Temperature Error vs 175 0111 1111 7F 1110 1111 EF Differential Capacitance. See the Filtering section for 191 0111 1111 7F 1111 1111 FF suggested component values where filtering (1) Resolution is 1°C/count. Negative numbers are represented in unwanted coupled signals is needed. twos complement format. (2) Resolution is 1°C/count. All values are unsigned with a –64°C offset. Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Link(s): TMP441 TMP442 |
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