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MAX6627 データシート(PDF) 6 Page - Maxim Integrated Products |
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MAX6627 データシート(HTML) 6 Page - Maxim Integrated Products |
6 / 9 page Remote ±1°C Accurate Digital Temperature Sensors with SPI-Compatible Serial Interface 6 _______________________________________________________________________________________ 0°C. When power is first applied and VCC rises above 1.6V (typ), the device starts to convert, although tem- perature reading is not recommended at VCC levels below 3.0V. Serial Interface Figure 2 is the serial interface timing diagram. The data is latched into the shift register on the falling edge of the CS signal and then clocked out at the SO pin on the falling edge of SCK with the most-significant bit (MSB) first. There are 16 edges of data per frame. The last 2 bits, D0 and D1, are always in high-Z mode. The falling edge of CS stops any conversion in progress, and the rising edge of CS always starts a new conversion and resets the interface. It is required to maintain a 320ms minimum pulse width of high CS signal before a con- version starts. Applications Information Remote-Diode Selection Temperature accuracy depends upon having a good- quality, diode-connected, small-signal transistor. Accuracy has been experimentally verified for all of the devices listed in Table 3. The MAX6627/MAX6628 can also directly measure the die temperature of CPUs and other ICs with on-board temperature-sensing diodes. The transistor must be a small-signal type with a rela- tively high forward voltage. This ensures that the input voltage is within the A/D input voltage range. The for- ward voltage must be greater than 0.25V at 10µA at the highest expected temperature. The forward voltage must be less than 0.95V at 100µA at the lowest expect- ed temperature. The base resistance has to be less than 100 Ω. Tight specification of forward-current gain (+50 to +150, for example) indicates that the manufac- turer has good process control and that the devices have consistent characteristics. ADC Noise Filtering The integrating ADC has inherently good noise rejec- tion, especially of low-frequency signals such as 60Hz/120Hz power-supply hum. Micropower operation places constraints on high-frequency noise rejection. Lay out the PC board carefully with proper external noise filtering for high-accuracy remote measurements in electrically noisy environments. Figure 2. SPI Timing Diagram D15 D0 D1 D2 D3 SCK SO tDV tCSS tDO CS tTR Table 3. SOT23-Type Remote-Sensor Transistor Manufacturers MANUFACTURER MODEL Central Semiconductor (USA) CMPT3904 Fairchild Semiconductor (USA) MMBT3904 Motorola (USA) MMBT3904 Rohm Semiconductor (Japan) SST3904 Siemens (Germany) SMBT3904 Zetex (England) FMMT3904CT-ND Note: Transistors must be diode connected (short the base to the collector). Table 2. Temperature Data Format (Two’s Complement) DIGITAL OUTPUT (BINARY) TEMPERATURE ( °C) D15–D3 D2 D1, D0 150 0,1001,0110,0000 0 XX 125 0,0111,1101,0000 0 XX 25 0,0001,1001,0000 0 XX 0.0625 0,0000,0000,0001 0 XX 0 0,0000,0000,0000 0 XX -0.0625 1,1111,1111,1111 0 XX -25 1,1110,0111,0000 0 XX -55 1,1100,1001,0000 0 XX |
同様の部品番号 - MAX6627 |
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同様の説明 - MAX6627 |
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