RT9726 High-Voltage Hysteresis Selectable Temperature Switch General Description Features The RT9726 is a temperature switch with wide input voltage range. The over-temperature threshold point is generated by a negative temperature coefficient (NTC) thermistor and a setting resistor. The RT9726 provides an active-low, opendrain logic output. OT goes LOW when the NTC pin voltage is lower than 50% of the REF voltage threshold. The RT9726 provides the selectable hysteresis mode that can be set by the EN pin Input voltage. The IC is available in SC-70-6 package. z z z z z z z Notebook Temperature Monitoring Microprocessor Thermal Management Temperature Control Fan Control z Electronic System Protection z z RT9726 Package Type U6 : SC-70-6 Lead Plating System G : Green (Halogen Free and Pb Free) 2 Selectable Hysteresis Threshold Reference Output for Thermal Threshold Setting Open-drain Logic Output RoHS Compliant and Halogen Free Applications z Ordering Information Wide Input Voltage Range : 4.75V to 25V 0.5μ μA Shutdown Current Pin Configurations (TOP VIEW) Note : EN REF OT 6 5 4 2 3 GND NTC Richtek products are : ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. VIN Marking Information A1=W SC-70-6 Typical Application Circuit 5V A1= : Product Code W : Date code 100k VIN 4.75V to 25V Chip Enable 3.3V 1 VIN C1 0.1µF 6 EN OT 4 RT9726 5 REF 2 GND NTC 3 System shutdown switch @ Temp = 100°C for default hysteresis 30°C DS9726-01 April 2011 System SHDN# R1 570 Thermistor ß = 4250 10k www.richtek.com 1 RT9726 Function Block Diagram VIN EN REF REF Hysteresis Control OT NTC + GND Functional Pin Description Pin No. Pin Name Pin Function 1 VIN High Voltage Power Supply Input. This pin should be bypassed with a 0.1μF capacitor to ground. 2 GND Ground pin. Tie the ground pin close to temperature sensing thermistor. 3 NTC This pin should connect a thermistor resistor to ground. The NTC pin will sense the external thermistor cross voltage and provide typical 50%REF over-temperature threshold for OT pin. 4 OT 5 REF 6 EN www.richtek.com 2 Open-drain and active-low output. OT will go LOW when NTC pin is lower than typical 50%REF over-temperature threshold. Reference Output. This pin should connect with a resistor to NTC pin to set the overtemperature threshold. Chip Enable (Active High). This pin can be used for the over-temperature threshold hysteresis setting. DS9726-01 April 2011 RT9726 Absolute Maximum Ratings z z z z z z z z (Note 1) VIN to GND -----------------------------------------------------------------------------------------------------------------NTC, OT, REF, EN to GND ---------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SC-70-6 ---------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SC-70-6, θJA ---------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions −0.3V to 28V −0.3V to 6V 0.3W 333°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 4.75V to 25V z Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Electrical Characteristics (No load on REF, VIN = 7V, VEN = 5V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit -- -- 3 μA -- 100 150 μA Input Supply VIN Shutdown Current IVIN VIN Quiescent Current IQ VIN = 4.75V to 25V, EN = GND VIN = 4.75V to 25V, EN = 5V, No Load On REF REF Output Voltage REF No External Load 1.978 2 2.022 V REF Output Current IREF In 1% REF Drop -- -- 2 mA OT Sink Current = 4mA -- -- 0.2 V OT = High 47.5 50 52.5 % Mode = Hyst1, OT = Low 62.5 65 67.5 % Mode = Hyst2, OT = Low 70 72.5 75 % Shutdown -- -- 0.4 V Set Hyst1 Mode 1.2 -- 2.4 V Set Hyst2 Mode 2.9 -- -- V REF Output Logic Output OT Output Low Voltage Temperature Threshold Configure Over-Temperature Threshold NTC/REF Over-Temperature Recovery Threshold NTC/REF EN Input Voltage DS9726-01 April 2011 EN www.richtek.com 3 RT9726 Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. www.richtek.com 4 DS9726-01 April 2011 RT9726 Typical Operating Characteristics Quiescent Current vs. Input Voltage Shutdown Current vs. Input Voltage 0.60 104 Shutdown Current (uA) Quiescent Current (uA) 105 103 102 101 0.55 0.50 0.45 VEN = 5V, No Load 100 VEN = 0V, No Load 0.40 5 7 9 11 13 15 17 19 21 23 25 5 VEN (2V/Div) VREF (2V/Div) VREF (5V/Div) OT (5V/Div) OT (5V/Div) VNTC (1V/Div) VNTC (1V/Div) Time (5ms/Div) 11 13 15 17 19 21 23 25 Over Temperature Recovery Threshold VEN (5V/Div) VIN = OT = 5V, CIN = 0.1μF 9 Input Voltage (V) Input Voltage (V) Start Up from EN 7 VEN = 1.8V, VIN = OT = 5V, CIN = 0.1μF Time (1ms/Div) Over Temperature Recovery Threshold VEN (5V/Div) VREF (5V/Div) OT (5V/Div) VNTC (1V/Div) VEN = 3.3V, VIN = OT = 5V, CIN = 0.1μF Time (1ms/Div) DS9726-01 April 2011 www.richtek.com 5 RT9726 Application Information The RT9726 is a temperature switch with wide input voltage range from 4.75V to 25V. It provides an accurate reference output voltage. By adding a negative temperature coefficient (NTC) thermistor from NTC pin to GND and a resistor from REF to NTC pin, a temperature-dependent voltage can be achieved. When the NTC pin voltage is lower than 50% of the REF voltage threshold, the OT pin goes low. The RT9726 provides a selectable hysteresis mode that can be set by controlling the EN pin voltage. Over Temperature Threshold Setting The OT pin state is an open-drain logic output. As shown in Table 1, the OT pin will go low and shut down the RT9726 when VNTC ≤ 50% of VREF. When VNTC > 50% of VREF, the OT pin will be pulled high by the external resistor. POR and Shutdown Power-on reset (POR) occurs when input voltage rises above 3.9V (typical), the OT pin will be released when VNTC is higher then 50% VREF. By setting the EN pin voltage below 0.4V, the REF pin voltage goes low and then the RT9726 will be shut down. Design Example Figure 1. shows the typical fan control application circuit. When the NTC pin voltage is lower than 50% of VREF, the OT will go low to turn on the fan. 5V 100k VIN 4.75V to 25V 1 Table 1. NTC Over Temperature Threshold OT 4 VIN C1 0.1µF RT9726 REF NTC Pin Voltage OT Pin State > 50% VREF Pulled High ≤ 50% VREF Low Over Temperature Recovery Threshold The RT9726 supports two temperature recovery thresholds as shown in the Table 2. It is set by EN pin voltage. For example, set EN pin voltage at 3.3V then OT pin will be released if VNTC rises to above 70% of the VREF. Table 2. Recovery Mode and NTC Recovery Threshold Voltage Recovery Mode EN Input Voltage NTC Pin Recovery Recovery Temperature Threshold (1) Threshold Voltage (min.) VEN = 1.2V 62.5% VREF −20°C to 2.4V VEN = Hyst 2 −30°C 2.9V to 70% VREF 5.5V Note 1 : Thermistor β = 4250 and temperature threshold RHYST Chip Enable 1.8V 6 EN 2 GND NTC 5 3 R1 1.29k Thermistor ß = 4250 10k Fan control switch @ Temp = 75°C for hysteresis 20°C Figure 1. Fan Control Application RT1 = RT2 × e β ⎛⎜ 1 − 1 ⎞⎟ T1 T2 ⎝ ⎠ RT1 : The resistance of NTC thermistor at T1 (Dk) RT2 : The resistance of NTC thermistor at T2 (Dk) β : The coefficient of NTC thermistor If the thermal shut-down threshold is set at 75°C and RT2 = 10kΩ (under 25°C) with β = 4250, R1 can be calculated by using the equation as follows : Hyst 1 R1 = R(T1 = 75DC) = 10k × e 1 1 ⎞ − 4250×⎛⎜ ⎟ ⎝ 273.15 +75 273.15 + 25 ⎠ = 1.29kΩ is set at 100°C. www.richtek.com 6 DS9726-01 April 2011 RT9726 Thermal Considerations Layout Considerations For continuous operation, do not exceed absolute maximum operation junction temperature. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. The maximum power dissipation can be calculated by following formula : For best performance of the RT9726, the input capacitor should be placed as close to the VIN pin and ground plane as possible to reduce noise coupling. The input capacitor should be placed as close as possible to the IC. VIN 6 EN C IN PD(MAX) = (TJ(MAX) − TA) / θJA Where T J(MAX) is the maximum operation junction temperature, TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. GND 2 5 REF NTC 3 4 OT Figure 3. PCB Layout Guide For recommended operating conditions specification of the RT9726, the maximum junction temperature is 125°C and TA is the maximum ambient temperature. The junction to ambient thermal resistance θJA is layout dependent. For SC-70-6 packages, the thermal resistance θJA is 333°C /W on the standard JEDEC 51-3 single layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : PD(MAX) = (125°C − 25°C) / (333°C / W) = 0.3W for SC-70-6 package The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. For RT9726 package, the Figure 2 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. Maximum Power Dissipation (W) 0.40 Single Layer PCB 0.35 0.30 0.25 SC-70-6 0.20 0.15 0.10 0.05 0.00 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curves for RT9726 Package DS9726-01 April 2011 www.richtek.com 7 RT9726 Outline Dimension H D L C B b A A1 e Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.800 1.100 0.031 0.044 A1 0.000 0.100 0.000 0.004 B 1.150 1.350 0.045 0.054 b 0.150 0.400 0.006 0.016 C 1.800 2.450 0.071 0.096 D 1.800 2.250 0.071 0.089 e 0.650 0.026 H 0.080 0.260 0.003 0.010 L 0.210 0.460 0.008 0.018 SC-70-6 Surface Mount Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. www.richtek.com 8 DS9726-01 April 2011