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TMP122/124 bảng dữ liệu(PDF) 5 Page - Texas Instruments |
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TMP122/124 bảng dữ liệu(HTML) 5 Page - Texas Instruments |
5 / 12 page TMP125 SBOS323A − DECEMBER 2004 − REVISED JUNE 2005 www.ti.com 5 APPLICATIONS The TMP125 10-bit, read-only digital temperature sensor is optimal for thermal management and thermal protection applications. The TMP125 is specified for a temperature range of −40 °C to +125°C, with operation extending down to −55 °C. It is specified for a supply voltage range of 2.7V to 5.5V, and also features a hardware shutdown to provide power savings. Quiescent current is reduced to 1 µA during analog shutdown. The TMP125 communicates through a serial interface that is SPI-compatible. Temperature is converted to a 10-bit data word with 0.25 °C resolution. The TMP125 is optimal for low-power applications, with a 120ms conversion period for reduced power consumption. The sensing device of the TMP125 is the chip itself. Thermal paths run through the package leads as well as the plastic package, and the lower thermal resistance of metal causes the leads to provide the primary thermal path. The TMP125 requires no external components for operation, though a 0.1 µF supply bypass capacitor is recommended. Figure 1 shows typical connection for the TMP125. TMP125 0.1 µF V+ 1 5 2 3 CS SI 4 6 SCK SO Figure 1. Typical Connections for the TMP125 COMMUNICATING WITH THE TMP125 The TMP125 continuously converts temperatures to digital data. Temperature data is read by pulling CS low. Once CS is pulled low, temperature data from the last completed conversion prior to dropping CS is latched into the shift register and clocked out at SO on the falling SCK edge. The 16-bit data word is clocked out sign bit first, followed by the MSB. The SI pin is used to put the device into shutdown mode. To enter shutdown mode, SI must be high on the rising edge of the third bit of SCK (see Figure 3). Also, all 16 bits must be clocked to allow shutdown on the TMP125. To bring the device out of shutdown, perform a 16-clock communication with SI set to logic low. The 16-clock communication is the same as the Data Read shown in Figure 3, except that the data on SO will be the last conversion prior to putting the device into shutdown mode. Note that SO is only used to control the shutdown function; if not using this function, connect this pin to ground. The one-shot command can be used to force a single conversion. When the command is issued, the part will perform a single conversion and then go into shutdown mode. After the conversion is complete, the conversion result should be read with the power-down bit high (see Figure 3) if you do not want to start a new conversion. The TMP125 will go into idle mode for 60ms, requiring only 20 µA of current. A new conversion begins every 120ms. Figure 2 describes the conversion timing for the TMP125. TEMPERATURE REGISTER The Temperature Register of the TMP125 is a 16-bit, read-only register that stores the output of the most recent conversion. However, temperature is represented by only 10-bits, which are in signed two’s complement format. The first bit of the Temperature Register, D15, is a leading zero. Bits D14 and D5 are used to indicate temperature. Bits D4 to D0 are the same as D5 (see Table 1). Data format for temperature is summarized in Table 2. When calculating the signed two’s complement temperature value, be sure to use only the 10 data bits. Following power-up or reset, the Temperature Register will read 0 °C until the first conversion is complete. D15 D14 D13 D12 D11 D10 D9 D8 0 T9 T8 T7 T6 T5 T4 T3 D7 D6 D5 D4 D3 D2 D1 D0 T2 T1 T0 T0 T0 T0 T0 T0 Table 1. Temperature Register TEMPERATURE ( °C) DIGITAL OUTPUT D14 …D5 +127 01 1111 1100 +125 01 1111 0100 +100 01 1001 0000 +75 01 0010 1100 +50 00 1100 1000 +25 00 0110 0100 +10 00 0010 1000 +0.25 00 0000 0001 0 00 0000 0000 −0.25 11 1111 1111 −25 11 1001 1100 −50 11 0011 1000 −55 11 0010 0100 Table 2. Temperature Data Format |
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Mô tả tương tự - TMP122/124 |
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