NCT65 Remote Trip Point Temperature Sensor with Overtemperature Shutdown Description http://onsemi.com The NCT65 is a low power temperature monitor housed in an MSOP8 package. It monitors the temperature of a remote thermal diode. The resulting temperature is then compared with fixed THERM limits (70C and 85C) and if the resulting temperature is greater than these limits, the open-drain THERM1 and THERM2 pins are asserted. To prevent constant assertion and deassertion of the THERM outputs the NCT65 has 5C of hysteresis. The NCT65 supply range is 2.8 V to 3.6 V and features low supply current making it suitable for portable applications. MSOP−8 RM SUFFIX CASE 846AB PIN CONNECTIONS Features Remote Temperature Sensor 0C − 85C Measurement Range Two Overtemperature THERM Shutdown Pins THERM1 Trip Point = 70C, THERM2 Trip Point = 85C Low Power Operation MSOP Package These Devices are Pb-Free, Halogen Free/BFR Free and are RoHS Compliant 1 VDD GND D+ THERM1 THERM2 GND (Top View) MARKING DIAGRAM Applications GND NCT65 D− 8 Smart Phones Consumer Electronics Embedded Systems Smart Batteries Desktop and Notebook Computers NCT65 AYWG G 1 NCT65 A Y W G = Specific Device Code = Assembly Location = Year = Work Week = Pb-Free Package (Note: Microdot may be in either location) ORDERING INFORMATION Device Package Shipping† NCT65DMR2G MSOP−8 (Pb-Free) 3,000/Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specification Brochure, BRD8011/D. Semiconductor Components Industries, LLC, 2012 August, 2012 − Rev. 1 1 Publication Order Number: NCT65/D NCT65 VDD 1 NCT65 T_TRIP = 85C REFERENCE + COMPARATOR 4 THERM2 6 THERM1 − D+ 2 LOW PASS FILTER DIFFERENCE AMPLIFIER D− 3 − COMPARATOR REFERENCE + T_TRIP = 70C 5 7 8 GND Figure 1. Functional Block Diagram Table 1. PIN FUNCTION DESCRIPTION Pin No. Pin Name 1 VDD Positive Supply Voltage. 2.8 V to 3.6 V. Description 2 D+ Positive Connection for Remote Temperature Sensor. 3 D− Negative Connection for Remote Temperature Sensor. 4 THERM2 Active-low Open-drain Over-temperature Output Pin; Needs a Pull-up Resistor. 5 GND 6 THERM1 Power Supply Ground. 7 GND Power Supply Ground. 8 GND Power Supply Ground. Active-low Open-drain Over-temperature Output Pin; Needs a Pull-up Resistor. http://onsemi.com 2 NCT65 Table 2. ABSOLUTE MAXIMUM RATINGS (Note 1) Parameter Positive Supply Voltage (VDD) to GND Rating Unit −0.3, +0.3 V −0.3 to VDD + 0.3 V D− to GND −0.3 to +3.6 V THERM −0.3 to +3.6 V D+ Input Current, THERM −1, +50 mA Input Current, D− 1 mA Maximum Junction Temperature 150 C −65 to 160 C 1,500 V 150 V Storage Temperature Range ESD Capability, Human Body Model (Note 2) ESD Capability, Machine Model (Note 2) Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. This device series incorporates ESD protection and is tested by the following methods: ESD Human Body Model tested per AEC−Q100−002 (EIA/JESD22−A114) ESD Machine Model tested per AEC−Q100−003 (EIA/JESD22−A115) 2. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area. Table 3. THERMAL CHARACTERISTICS (Note 3) Symbol Rating Thermal Characteristics, MSOP (Note 4) Thermal Resistance, Junction-to-Air Value Unit C/W 142 RqJA 3. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area. 4. As measured using a copper heat spreading area of 650 mm2 (or 1 in2), of 1 oz copper thickness. Table 4. OPERATING RANGES (Note 5) Symbol Min Max Unit Operating Input Voltage VIN 2.8 3.6 V Operating Ambient Temperature Range TA −40 125 C Rating 5. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area. Table 5. ELECTRICAL CHARACTERISTICS (TA = TMIN to TMAX, VDD = 2.8 V to 3.6 V. All specifications for −40C to +125C, unless otherwise noted.) Parameter Test Conditions Min Typ Max Unit POWER SUPPLY 2.8 3.3 3.6 V Average Operating Supply Current, IDD − − 1.15 mA Undervoltage Lockout Threshold − 2.55 − V Supply Voltage VDD TRIP POINT ACCURACY Trip Point Accuracy at VDD = 2.8 V to 3.6 V TA = 0C to +70C TA = 0C to +85C − − − − 1 1.5 C Response Time Temperature Measurement to THERM Assertion − 40 52 ms Output Low Voltage, VOL IOL = −6.0 mA − − 0.4 V High Output Leakage Current, IOH VOUT = VDD − 0.1 1.0 mA Hysteresis The temperature must drop by this amount below the THERM trippoints before the pins will de-assert − 5 − C OPEN DRAIN OUTPUT (THERM) http://onsemi.com 3 NCT65 Theory of Operation To prevent ground noise interfering with the measurement, the more negative terminal of the sensor is not referenced to ground but is biased above ground by an internal diode at the D− input. If the sensor is operating in a noisy environment an optional filter can be added. Its value should be no more than 1,000 pF. See the Layout Considerations section for more information on C1. To measure DVBE, the operating current through the sensor is switched among three related currents. N1 I and N2 I are different multiples of the current, I. The currents through the temperature diode are switched between I and N1 I, giving DVBE1; and then between I and N2 I, giving DVBE2. The temperature is then calculated using the two DVBE measurements. This method also cancels the effect of any series resistance on the temperature measurement. The resulting waveform is passed through a 65 kHz low-pass filter to remove noise, and then to a chopper-stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage proportional to DVBE. This voltage is input into two comparators with a reference voltage. If the voltage exceeds the reference voltage then the THERM output asserts low. The NCT65 is a remote trip point temperature sensor for use in a vide variety of applications from smart phones to embedded systems. The remote temperature is measured by the NCT65 and then compared with a fixed limit set by the internal device reference. The limit for the THERM1 pin is 70C and the limit for the THERM2 pin is 85C. If either the remote temperature exceeds the defined limits the open drain THERM pins are asserted low. Each THERM pin self clears when the temperature drops 5C below the THERM limit. This is to prevent THERM jitter, where the temperature hovers around the THERM limit. THERM2 = 85 Hyst = 5 Temperature THERM1 = 70 Hyst = 5 Time Applications Information THERM2 Noise Filtering For temperature sensors operating in noisy environments, the industry standard practice was to place a capacitor across the D+ and D− pins to help combat the effects of noise. However, large capacitances affect the accuracy of the temperature measurement, leading to a recommended maximum capacitor value of 1,000 pF. Although this capacitor reduces the noise, it does not eliminate it, making it difficult to use the sensor in a very noisy environment. The NCT65 has a major advantage over other devices when it comes to eliminating the effects of noise on the external sensor. The series resistance cancellation feature allows a filter to be constructed between the external temperature sensor and the part. The effect of any filter resistance seen in series with the remote sensor is automatically cancelled from the temperature result. The construction of a filter allows the NCT65 and the remote temperature sensor to operate in noisy environments. The figure below shows a low-pass R-C-R filter, where R = 100 W and C = 1 nF. This filtering reduces both common-mode and differential noise. THERM1 Figure 2. Trippoints Measurement Method A simple method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at constant current. Unfortunately, this technique requires calibration to null out the effect of the absolute value of VBE, which varies from device to device. The technique used in the NCT65 is to measure the change in VBE when the device is operated at three different currents. This is given by: DV BE + (n f) kT q In(N) (eq. 1) Where: k is Boltzmann’s constant (1.38 10–23). q is the charge on the electron (1.6 10–19 Coulombs). T is the absolute temperature in Kelvins. N is the ratio of the two currents. nf is the ideality factor of the thermal diode. 100 W REMOTE TEMPERATURE SENSOR 100 W D+ 1 nF D− Figure 3. Filter between Remote Sensor and Factors Affecting Diode Accuracy The NCT65 is trimmed for an ideality factor of 1.008. http://onsemi.com 4 NCT65 Remote Sensing Diode capacitor across D+ and D− close to the NCT65. This capacitance can effect the temperature measurement, so ensure that any capacitance seen at D+ and D− is, at maximum, 1,000 pF. This maximum value includes the filter capacitance, plus any cable or stray capacitance between the pins and the sensor diode. The NCT65 is designed to work with substrate transistors built into processors or with discrete transistors. Substrate transistors are generally PNP types with the collector connected to the substrate. Discrete types are either PNP or NPN transistors connected as diodes (base-shorted to collector). If an NPN transistor is used, the collector and base are connected to D+ and the emitter to D−. If a PNP transistor is used, the collector and base are connected to D− and the emitter to D+. GND 5 MIL 5 MIL D+ 5 MIL 5 MIL Layout Considerations Digital boards can be electrically noisy environments, and the NCT65 is measuring very small voltages from the remote sensor, so care must be taken to minimize noise induced at the sensor inputs. Take the following precautions: Place the NCT65 as close as possible to the remote sensing diode. Provided that the worst noise sources, that is, clock generators, data/address busses etc., are avoided, this distance can be 4 to 8 inches. Route the D+ and D− tracks close together, in parallel, with grounded guard tracks on each side. To minimize inductance and reduce noise pickup, a 5 mil track width and spacing is recommended. Provide a ground plane under the tracks, if possible. Place a 0.1 mF bypass capacitor close to the VDD pin. In extremely noisy environments, place an input filter 5 MIL D− 5 MIL GND 5 MIL Figure 4. Typical Arrangement of Signal Tracks Application Circuit The figure below shows a typical application circuit for the NCT65, using an embedded transistor on a GPU to measure the temperature. The THERM1 pin can be used to alert the system and throttle the GPU. The THERM2 pin can be used to shutdown the system if necessary. Both pins require pullup resistors to VDD or an alternative supply (up to 3.6 V). VDD V+ (up to 3.6 V) 1 NCT65 10 kW T_TRIP = 85C REFERENCE + COMPARATOR 4 THERM2 − D+ 2 GPU D− LOW PASS FILTER DIFFERENCE AMPLIFIER 10 kW 3 − COMPARATOR REFERENCE + T_TRIP = 70C 5 7 8 GND Figure 5. Typical Configuration Block Diagram http://onsemi.com 5 6 THERM1 NCT65 PACKAGE DIMENSIONS MSOP8 CASE 846AB−01 ISSUE O D HE PIN 1 ID NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.15 (0.006) PER SIDE. 4. DIMENSION B DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. INTERLEAD FLASH OR PROTRUSION SHALL NOT EXCEED 0.25 (0.010) PER SIDE. 5. 846A-01 OBSOLETE, NEW STANDARD 846A-02. E e b 8 PL 0.08 (0.003) M T B S A S SEATING −T− PLANE 0.038 (0.0015) A A1 MILLIMETERS NOM MAX −− 1.10 0.08 0.15 0.33 0.40 0.18 0.23 3.00 3.10 3.00 3.10 0.65 BSC 0.40 0.55 0.70 4.75 4.90 5.05 DIM A A1 b c D E e L HE MIN −− 0.05 0.25 0.13 2.90 2.90 INCHES NOM −− 0.003 0.013 0.007 0.118 0.118 0.026 BSC 0.021 0.016 0.187 0.193 MIN −− 0.002 0.010 0.005 0.114 0.114 MAX 0.043 0.006 0.016 0.009 0.122 0.122 0.028 0.199 L c SOLDERING FOOTPRINT* 8X 1.04 0.041 0.38 0.015 3.20 0.126 6X 8X 4.24 0.167 0.65 0.0256 5.28 0.208 SCALE 8:1 mm Ǔ ǒinches *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). 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