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TMP435ADGSR Scheda tecnica(PDF) 9 Page - Texas Instruments |
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TMP435ADGSR Scheda tecnica(HTML) 9 Page - Texas Instruments |
9 / 35 page TMP435 www.ti.com SBOS495A – MARCH 2010 – REVISED APRIL 2010 APPLICATION INFORMATION correct for any changes in the beta factor as a result The TMP435 (two-channel) is a digital temperature of temperature variation. The device can operate a sensor that combines a local die temperature PNP transistor with a beta factor as low as 0.1. See measurement channel and a remote junction the Beta Compensation Configuration Register temperature measurement channel in a single section for further information. package. This device is two-wire- and SMBus interface-compatible, and is specified over a Series Resistance Cancellation temperature range of –40°C to +125°C. The TMP435 contains multiple registers for holding configuration Series resistance in an application circuit that typically information, temperature measurement results, results from printed circuit board (PCB) trace temperature comparator maximum/minimum limits, resistance and remote line length is automatically and status information. User-programmed high and cancelled by the TMP435, preventing what would low temperature limits stored in the TMP435 can be otherwise result in a temperature offset. A total of up used to trigger an over/under temperature alarm to 1k Ω of series line resistance is cancelled by the (ALERT) on local and remote temperatures. TMP435 if beta correction is disabled and up to 300 Ω Additional thermal limits can be programmed into the of series line resistance is canceled if beta correction TMP435 and used to trigger another flag (THERM) is enabled, eliminating the need for additional that can be used to initiate a system response to characterization and temperature offset correction. rising temperatures. See the two Remote Temperature Error vs Series Resistance typical characteristic curves (Figure 7 and For proper remote temperature sensing operation, the Figure 8) for details on the effect of series resistance TMP435 requires only a transistor connected on sensed remote temperature error. between DXP and DXN. The SCL and SDA interface pins require pull-up Differential Input Capacitance resistors as part of the communication bus, while The TMP435 can tolerate differential input ALERT and THERM are open-drain outputs that also capacitance of up to 2200pF with minimal change in need pull-up resistors. ALERT and THERM may be temperature error. The effect of capacitance on shared with other devices if desired for a wired-OR sensed remote temperature error is illustrated in implementation. A 0.1mF power-supply bypass Figure 9 and Figure 10, Remote Temperature Error capacitor is recommended for good local bypassing. vs Differential Capacitance. See the Filtering section See Figure 13 for a typical configuration. for suggested component values where filtering unwanted coupled signals is needed. Beta Compensation Previous generations of remote junction temperature Temperature Measurement Data sensors were operated by controlling the emitter Temperature measurement data are taken over a current of the sensing transistor. However, default range of 0°C to +127°C for both local and examination of the physics of a transistor shows that remote locations. However, measurements from VBE is actually a function of the collector current. If –55°C to +150°C can be made both locally and beta is independent of the collector current, then VBE remotely by reconfiguring the TMP435 for the may be calculated from the emitter current. In earlier extended temperature range, as described in this generations of processors that contained PNP section. Temperature data resulting from conversions transistors connected to these temperature sensors, within the default measurement range are controlling the emitter current provided acceptable represented in binary form, as shown in Table 1, temperature measurement results. At 90nm process Standard Binary column. Note that any temperature geometry and below, the beta factor continues to below 0°C results in a data value of zero (00h). decrease and the premise that it is independent of Likewise, temperatures above +127°C result in a collector current becomes less certain. value of 127 (7Fh). The device can be set to measure To manage this increasing temperature measurement over an extended temperature range by changing bit error, the TMP435 controls the collector current 2 (RANGE) of Configuration Register 1 from low to instead of the emitter current. The TMP435 high. The change in measurement range and data automatically detects and chooses the correct range format from standard binary to extended binary depending on the beta factor of the external occurs at the next temperature conversion. transistor. This auto-ranging is performed at the beginning of each temperature conversion in order to Copyright © 2010, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Link(s): TMP435 |
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