PDF NCT72 Data sheet ( Hoja de datos )

Número de pieza	NCT72
Descripción	Temperature Monitor
Fabricantes	ON Semiconductor
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No Preview Available ! NCT72 +15C Temperature Monitor with Series Resistance Cancellation The NCT72 is a dual-channel digital thermometer and undertemperature/overtemperature alarm, intended for use in PCs and thermal management systems. It is pin and register compatible with the NCT1008 but the NCT72 allows the user to pull the ALERT pin to 1.8 V without increasing the device Idd. A feature of the NCT72 is series resistance cancellation, where up to 1.5 kW (typical) of resistance in series with the temperature monitoring diode can be automatically cancelled from the temperature result, allowing noise filtering. The NCT72 has a configurable ALERT output and an extended, switchable temperature measurement range. The NCT72 can measure the temperature of a remote thermal diode accurate to 1C and the ambient temperature accurate to 3C. The temperature measurement range defaults to 0C to +127C, compatible with the NCT1008, but it can be switched to a wider measurement range of −64C to +191C. The NCT72 communicates over a 2-wire serial interface, compatible with system management bus (SMBus/I2C) standards. The default SMBus/I2C address of the NCT72 is 0x4C. An NCT72D is available with an SMBus/I2C address of 0x4D. This is useful if more than one NCT72 is used on the same SMBus/I2C. An ALERT output signals when the on-chip or remote temperature is out of range. The THERM output is a comparator output that allows on/off control of a cooling fan. The ALERT output can be reconfigured as a second THERM output, if required. Features  On-chip and Remote Temperature Sensor  0.25C Resolution/1C Accuracy on Remote Channel  1C Resolution/1C Accuracy on Local Channel  Series Resistance Cancellation Up to 1.5 kW  Extended, Switchable Temperature Measurement Range 0C to +127C (Default) or –64C to +191C  Pin and Register Compatible with NCT1008  Remote THERM Limit of 108C  2-wire SMBus/I2C Serial Interface with SMBus Alert Support  Programmable Over/Undertemperature Limits  Offset Registers for System Calibration  Up to Two Overtemperature Fail-safe THERM Outputs  Small 8-lead DFN  240 mA Operating Current, 5 mA Standby Current  Compatible with 1.8 V Logic  These Devices are Pb-Free, Halogen Free/BFR Free and are RoHS Compliant Applications  Smart Phones  Desktop and Notebook Computers  Smart Batteries  Automotive  Embedded Systems  Semiconductor Components Industries, LLC, 2012 August, 2012 − Rev. 4 1 http://onsemi.com WDFN8 CASE 511AT DFN8 CASE 506BJ PIN ASSIGNMENT VDD 1 8 SCLK D+ 2 D− 3 THERM 4 7 SDATA 6 ALERT/ THERM2 5 GND (Top View) MARKING DIAGRAMS 1 7xMG G WDFN8 7x = Device Code (Where x = C or D) M = Date Code G = Pb-Free Package (Note: Microdot may be in either location) 1 NCT 8 72x ALYWG G DFN8 x = C or D A = Assembly Location L = Wafer Lot Y = Year W = Work Week G = Pb-Free Package (Note: Microdot may be in either location) ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 18 of this data sheet. Publication Order Number: NCT72/D 1 page NCT72 TYPICAL PERFORMANCE CHARACTERISTICS 3.5 DEV 1 DEV 8 DEV 15 3.0 DEV 2 DEV 9 DEV 16 DEV 3 DEV 10 MEAN 2.5 DEV 4 DEV 11 HIGH 4R DEV 5 DEV 12 LOW 4R 2.0 DEV 6 DEV 7 DEV 13 DEV 14 1.5 1.0 0.5 0 −0.5 −1.0 −50 0 50 100 TEMPERATURE (C) 150 Figure 3. Local Temperature Error vs. Temperature 10 5 D+ To GND 0 −5 −10 D+ To VDD −15 −20 −25 1 10 100 LEAKAGE RESISTANCE (MW) Figure 5. Temperature Error vs. D+/D− Leakage Resistance 3.5 DEV 1 DEV 8 DEV 15 3.0 DEV 2 DEV 9 DEV 16 DEV 3 DEV 10 HIGH 4R 2.5 DEV 4 DEV 11 LOW 4R DEV 5 DEV 12 2.0 DEV 6 DEV 13 DEV 7 DEV 14 1.5 1.0 0.5 0 −0.5 −1.0 −50 0 50 100 TEMPERATURE (C) 150 Figure 4. Remote Temperature Error vs. Actual Temperature 0 −2 −4 −6 −8 −10 DEV 3 −12 DEV 2 −14 DEV 4 −16 −18 0 5 10 15 20 CAPACITANCE (nF) 25 Figure 6. Temperature Error vs. D+/D− Capacitance 1000 900 DEV 2BC 800 700 600 500 DEV 4BC 400 300 DEV 3BC 200 100 0 0.01 0.1 1 10 CONVERSION RATE (Hz) Figure 7. Operating Supply Current vs. Conversion Rate 100 422 420 DEV 2BC 418 416 414 DEV 3BC DEV 4BC 412 410 408 3.0 3.1 3.2 3.3 3.4 3.5 3.6 VDD (V) Figure 8. Operating Supply Current vs. Voltage http://onsemi.com 5 5 Page NCT72 set, the THERM2 output goes low to indicate that the temperature measurements are outside the programmed limits. Flag 5 and Flag 3 have no effect on THERM2. The behavior of THERM2 is otherwise the same as THERM. Table 10. STATUS REGISTER BIT ASSIGNMENTS Bit Name Function 7 BUSY 1 when ADC Is Converting 6 LHIGH 1 when Local High Temperature Limit is (Note 1) Tripped 5 LLOW 1 when Local Low Temperature Limit is (Note 1) Tripped 4 RHIGH 1 when Remote High Temperature Limit (Note 1) is Tripped 3 RLOW 1 when Remote Low Temperature Limit (Note 1) is Tripped 2 OPEN 1 when Remote Sensor is an Open (Note 1) Circuit 1 RTHRM 1 when Remote THERM Limit is Tripped 0 LTHRM 1 when Local THERM Limit is Tripped 1. These flags stay high until the status register is read or they are reset by POR unless Pin 6 is configured as THERM2. Then, only Bit 2 remains high until the status register is read or is reset by POR. Offset Register Offset errors can be introduced into the remote temperature measurement by clock noise or when the thermal diode is located away from the hot spot. To achieve the specified accuracy on this channel, these offsets must be removed. The offset value is stored as a 10-bit, twos complement value in Register 0x11 (high byte) and Register 0x12 (low byte, left justified). Only the upper two bits of Register 0x12 are used. The MSB of Register 0x11 is the sign bit. The minimum, programmable offset is −128C, and the maximum is +127.75C. The value in the offset register is added to, or subtracted from, the measured value of the remote temperature. The offset register powers up with a default value of 0C and has no effect unless the user writes a different value to it. Table 11. SAMPLE OFFSET REGISTER CODES Offset Value −128C −4C −1C −0.25C 0C +0.25C +1C +4C +127.75C 0x11 1000 0000 1111 1100 1111 1111 1111 1111 0000 0000 0000 0000 0000 0001 0000 0100 0111 1111 0x12 00 00 0000 00 00 0000 00 000000 10 00 0000 00 00 0000 01 00 0000 00 00 0000 00 00 0000 11 00 0000 One-shot Register The one-shot register is used to initiate a conversion and comparison cycle when the NCT72 is in standby mode, after which the device returns to standby. Writing to the one-shot register address (0x0F) causes the NCT72 to perform a conversion and comparison on both the internal and the external temperature channels. This is not a data register as such, and it is the write operation to Address 0x0F that causes the one-shot conversion. The data written to this address is irrelevant and is not stored. Consecutive ALERT Register The value written to this register determines how many out-of-limit measurements must occur before an ALERT is generated. The default value is that one out-of-limit measurement generates an ALERT. The maximum value that can be chosen is 4. The purpose of this register is to allow the user to perform some filtering of the output. This is particularly useful at the fastest three conversion rates, where no averaging takes place. This register is at Address 0x22. Table 12. CONSECUTIVE ALERT REGISTER CODES Register Value Number of Out-of-limit Measurements Required yxxx 000x 1 yxxx 001x 2 yxxx 011x 3 yxxx 111x 4 NOTE: x = don’t care bits, and y = SMBus timeout bit. Default = 0. See SMBus section for more information. http://onsemi.com 11 11 Page

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