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FM75 데이터시트(PDF) 6 Page - Fairchild Semiconductor |
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FM75 데이터시트(HTML) 6 Page - Fairchild Semiconductor |
6 / 16 page © 2006 Fairchild Semiconductor Corporation www.fairchildsemi.com FM75 Rev. 1.0.8 6 Basic Operation The FM75 temperature sensing circuitry continuously produces analog voltage proportional to the device tem- perature. At regular intervals, the FM75 converts the analog voltage to a two’s complement digital value, which is placed into the temperature register. The FM75 has an SMBus-compatible digital serial inter- face that allows access to the data in the temperature register at any time. In addition, the serial interface pro- vides access to all other FM75 registers to customize operation of the device. The FM75 temperature-to-digital conversion can have 9, 10, 11, or 12-bit resolution selected, providing 0.5°C, 0.25°C, 0.125°C, and 0.0625°C temperature resolution, respectively. At power-up, the default conversion resolu- tion is 9-bits. The conversion resolution is controlled by the R0 and R1 bits in the configuration register. Table 1 gives examples of the relationship between the output digital data and the external temperature. The 9-bit, 10-bit, 11-bit, and 12-bit columns in Table 1 indicate the right-most bit in the output data stream that can con- tain temperature information for each conversion accu- racy. Since the output digital data is in two’s-complement format, the most significant bit of the temperature is the “sign” bit. If the sign bit is zero, the temperature is posi- tive; if the sign bit is one, the temperature is negative. The FM75 has a shutdown mode that reduces the oper- ating current to 150nA. This mode is controlled by the SD bit in the configuration register. Power-Up Default Conditions The FM75 powers up in the following default state: • Thermostat mode: comparator mode • OS polarity: active LOW • Fault tolerance: 1 fault (i.e., F0 = 0 and F1 = 0 in the configuration register) •TOS: 80°C •THYST: 75°C • Register pointer: 00 (temperature register) • Conversion resolution: 9 bits (i.e., R0 = 0 and R1 = 0 in the configuration register) After power-up, these conditions can be reprogrammed via the serial interface. Refer to the Serial Data Bus Operation section for FM75 programming instructions. Thermal Alarm Function The FM75 thermal alarm function provides programma- ble thermostat capability and allows the FM75 to function as a stand-alone thermostat without using the serial interface. The Over-Limit Signal (OS) output is the alarm output. This signal is an open-drain output and, at power-up, this pin is configured with active-low polarity. Table 1. Relationship Between Temperature and Digital Output The OS polarity is controlled by the POL bit in the config- uration register. The programmable upper trip-point tem- perature for the thermal alarm is stored in the TOS register. The programmable hysteresis temperature (i.e., the lower trip point) is stored in the THYST register. The thermal alarm has two modes of operation: compar- ator mode and interrupt mode. At power-up, the default is comparator mode. The alarm mode is controlled by the CMP/INTR bit in the configuration register. Fault Tolerance For both comparator and Interrupt modes, the alarm “fault tolerance” setting plays a role in determining when the OS output is activated. Fault tolerance refers to the number of consecutive times an error condition must be detected before the user is notified. Higher fault toler- ance settings can help eliminate false alarms caused by noise in the system. The alarm fault tolerance is con- trolled by bits F0 and F1 in the configuration register. These bits can be used to set the fault tolerance to 1, 2, 4, or 6, as shown in Table 4. At power-up, these bits both default to 0 (fault tolerance = 1). Temperature Digital Output g i S f o r e b m u N d e s u s t i b y b n o i s r e v n o c n o i t u l o s e r t i b 9 t i b 0 1 t i b 1 1 t i b 2 1 s y a w l A o r e z ll A s e r u t a r e p m e T n o i t u l o s e R t i B - 2 1 0 0 0 0 n o i t u l o s e R t i B - 11 0 0 0 0 0 n o i t u l o s e R t i B - 10 0 0 0 0 0 0 n o i t u l o s e R t i B - 90 0 0 0 0 0 0 C 5 2 1 + 01 1 11 0 1 10 0 0 0 0 0 0 0 C 5 2 6 0 . 0 0 1 + 00 1 10 0 1 00 0 0 1 0 0 0 0 C 5 2 1 . 0 5 + 01 1 00 1 0 00 0 1 0 0 0 0 0 C 5 2 . 2 1 + 00 0 00 0 1 10 1 0 0 0 0 0 0 C 0 00 0 00 0 0 00 0 0 0 0 0 0 0 C 5 . 0 2 - 10 1 11 1 0 11 0 0 0 0 0 0 0 C 5 2 . 3 3 - 11 0 10 1 1 11 1 0 0 0 0 0 0 C 5 2 6 0 . 5 4 - 11 0 10 1 0 01 1 1 1 0 0 0 0 C 5 5 - 10 0 11 0 0 10 0 0 0 0 0 0 0 |
유사한 부품 번호 - FM75_06 |
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유사한 설명 - FM75_06 |
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