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MAX6511UT045 Datasheet(PDF) 5 Page - Maxim Integrated Products |
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MAX6511UT045 Datasheet(HTML) 5 Page - Maxim Integrated Products |
5 / 8 page Hysteresis Input The HYST pin is a CMOS-compatible input that selects hysteresis at either a high level (10°C for HYST = VDD) or a low level (5°C for HYST = GND). Hysteresis pre- vents the output from chattering when the temperature is near the trip point. The HYST pin must not float. The output asserts when the temperature exceeds the trip point and deasserts when the temperature falls back below the trip point minus the hysteresis. For example, if the trip point is 105°C, the output will assert at 105°C and will not deassert until temperature falls below 105°C minus the hysteresis (e.g., 95°C if 10°C hysteresis is chosen) (Figure 2). Applications Information Remote-Diode Selection To ensure best accuracy, use a good-quality diode- connected transistor. Suggested devices are listed in Table 1. Large power transistors are not recommend- ed. Tight specifications for forward current gain indi- cate the manufacturer has good process controls and that the devices have consistent Vbe characteristics. The MAX6511/MAX6512/MAX6513 can also measure the die temperature of CPUs and other integrated cir- cuits having on-board temperature-sensing diodes. Use the monitor’s output to reset the µP, assert an inter- rupt, activate a cooling fan, or trigger an external alarm. Noise Filtering Capacitors A quality ceramic capacitor must be connected across the DXP/DXN inputs to maintain temperature threshold accuracy by filtering out noise. The capacitor should be located physically close to the DXP/DXN pins and should typically have a value of 2200pF. Larger capaci- tor values can cause temperature measurement errors. A 50% variation from the recommended capacitor value can cause up to ±1°C error. Low-Cost, Remote SOT Temperature Switches _______________________________________________________________________________________ 5 Figure 2. Temperature Trip Threshold Hysteresis TRIP TEMPERATURE TRIP TEMPERATURE HYSTERESIS TOVER (MAX6511) TIME MANUFACTURER MODEL NUMBER Central Semiconductor (USA) CMPT3904 ON (USA) MMBT3904 Rohm Semiconductor (Japan) SST3904 Samsung (Korea) KST3904-TF Siemens (Germany) SMBT3904 Zetex (England) FMMT3904CT-ND Table 1. Sensor Transistor Manufacturers Note: Transistors must be diode connected (base shorted to collector). |
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