NCT3941STR

NCT3941S/S-A Nuvoton 4 Times Linear Fan Driver NCT3941S/S-A -I- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A Table of Content1. GENERAL DESCRIPTION................................................................................. 1 2. FEATURES ........................................................................................................ 1 3. APPLICATION ................................................................................................... 1 4. BLOCK DIAGRAM ............................................................................................. 2 5. PIN CONFIGURATION AND TYPICAL APPLICATION CIRCUIT...................... 2 6. PIN DESCRIPTION............................................................................................ 4 7. FUNCTIONAL DESCRIPTION........................................................................... 4 8. ELECTRICAL CHARACTERISTIC..................................................................... 7 9. OPERATING CHARACTERISTICS ................................................................... 9 10. PACKAGE DIMENSION .................................................................................. 15 11. ORDERING INFORMATION............................................................................ 16 12. TOP MARKING SPECIFICATION.................................................................... 16 13. REVISION HISTORY ....................................................................................... 17 -II- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A 1. GENERAL DESCRIPTION The NCT3941S/S-A is a simply linear fan driver. It is designed for noise-sensitive or powersensitive applications that require system cooling. The NCT3941S/S-A is a low quiescent current, low dropout linear regulator which is designed with a P-channel MOSFET to power a DC fan and delivers output current up to 500mA. The output voltage follows the 4 times on the voltage of VSET pin to dynamic adjust the DC fan speed. NCT3941S supports enable pin to control the output voltage. NCT3941S-A supports fully turn-on function. NCT3941S/S-A is available in SOP8-EP package. 2. FEATURES z VOUT Follows 4 Times of VSET z 0.5V Dropout @ 0.5A Output Current z Continues current up to 500mA, current limit trip threshold 1.6A z Enable Function (NCT3941S) z Full Turn On Function (NCT3941S-A) z Short Circuit and Over Temperature Protections z Low External Component Count z Low Cost and Easy to Use z SOP8 150mil with Exposed Pad Package z Green Package (Lead Free and Halogen Free) 3. APPLICATION z Projectors z Peripheral Add-in Cards z Motherboards z Battery Powered Systems -1- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A 4. BLOCK DIAGRAM Internal Regulator ENABLE (FON#) GND VIN 1 VOUT Current Limit 3uA 3 Enable/FON# Logic VSET 2 Thermal Shutdown 4 R1 6 R1=3R2 R2 (FON#) ARE FOR NCT3941S-A 5. PIN CONFIGURATION AND TYPICAL APPLICATION CIRCUIT VOUT 1 VIN 2 ENABLE (FON#) 3 VSET Thermal Pad 4 8 NC 7 NC 6 GND 5 NC NCT3941S/ S-A (Top View) (FON#) ARE FOR NCT3941S-A -2- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A VCC ENABLE (FON#) VIN CIN 2.2uF Input Signal VOUT COUT 10uF VSET DC Voltage GND FAN Typical Application Circuits FAN_12V ATX_12VCC Cout 10U Cin 2.2U Vout Vin EN(FON#) Vset VEN SIO_FANOUT(VOLTAGE MODE) N.C N.C GND N.C NCT3941S/S-A VOLTAGE MODE (FON#) ARE FOR NCT3941S-A FAN_12V ATX_12VCC Cout 10U Cin 2.2U Vout Vin EN(FON#) Vset VEN N.C N.C GND N.C +3.3VC.C R1 NCT3941S/S-A 1k SIO_FANOUT(PWM MODE) R2 100k C1 1U PWM MODE -3- (FON#) ARE FOR NCT3941S-A Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A 6. PIN DESCRIPTION NO PIN NAME PIN TYPE DESCRIPTION 1 AO Voltage output pin. Connect a low ESR ceramic capacitor (10uF, typically) to ground to assure stability. 2 POWER DC power supply input. Connect a bypass capacitor (2.2uF, typically) is recommended. I Enable pin. Output voltage follows 4 times of VSET pin voltage when ENABLE pin at high level. Internal pull high is implemented. NCT3941S NCT3941S-A VOUT 1 VIN 2 ENABLE 3 FON# 3 I Full On mode selection pin. Output voltage follows 4 times of VSET pin voltage when FON# pin at high level. The internal power MOSFET full turns on when FON# pin at low level. Internal pull high is implemented. Output voltage setting pin. The inputs could be DC voltage. The input voltage must be larger that 1V. VSET 4 4 AIN GND 6 6 GROUND NC 5, 7, 8 5, 7, 8 PIN TYPE Output pin (Analog) AIN Input pin (Analog) I Input pin (Digital) GROUND No internal connection. PIN Attribute AO POWER Power supply ground. Positive power supply input Power supply ground 7. FUNCTIONAL DESCRIPTION 7.1 VSET Setting The output voltage is 4 times of VSET pin voltage. When the VSET voltage exceeds 1V, the output voltage will follow 4 times of VSET voltage. -4- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A 7.2 Enable Function This function is for NCT3941S only. The input voltage level of ENABLE pin can control the internal regulator turn on or turn off. When pulling this pin below 0.3V, the regulator will be turned off. When pulling this pin above 1V, the regulator will be turned on. 7.3 Full On Function This function is for NCT3941S-A only. The input voltage level of FON# can control the internal regulator fully turn on or following 4 times of VSET voltage. When pulling this pin below 0.3V, the regulator will be fully turned on. When pulling this pin above 1.6V, the output voltage will follow 4 times of VSET voltage. 7.4 Short Circuit Current Limit The NCT3941S/S-A provides a current limit circuitry for short circuit protection, which monitors the output current and controls PMOS gate voltage to limit the output current at 200mA. 7.5 Thermal Consideration The NCT3941S/S-A has a thermal shutdown circuitry to limit the junction temperature. When the junction temperature exceeds 150°C, the thermal shutdown circuit disables the output, allowing the device to cool down. The output circuitry is enabled again after the junction temperature cools down by 30°C, resulting in a pulsed output during continuous thermal overload conditions. The thermal protection is designed to protect the IC in the event of over temperature conditions. For reliabile operation, the junction temperature cannot exceed 125°C. The definition of power dissipation in chip is as following equation: PD = (VIN - VOUT) x IOUT + VIN x IQ PD represents the power dissipation. The power dissipation depends on the thermal resistance of chip package, PCB layout, the airflow and temperature difference between junction and ambient. Refers to JEDEC51-1, The power dissipation can be calculated by following equation: PD(MAX) = (TJ(MAX) - TA) / θJA Where TJ(MAX) is the maximum operation junction temperature 125℃, TA is the ambient temperature and theθJA is the junction to ambient thermal resistance. θJA for ESOP-8 package is 75℃/W on JEDEC51-7 (4 layers, 2S2P) thermal test board with minimum copper area. The maximum power dissipation at TA = 25℃ can be calculated as: PD(MAX) = (125℃ - 25℃) / 75℃/W = 1.33W -5- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A θ JA highly depends on IC package, PCB layout, the aireflow. Thermal resistance θ JA can be improved by adding copper under the exposed pad of ESOP-8 while the IC package is fixed. The copper under the exposed pad of ESOP-8 is an effective heatsink and is useful for improving thermal conductivity. Figure show the relationship between thermal resistance θ JA vs. copper area on a standard JEDEC 51-7 (4 layers, 2S2P) thermal test board at TA = 25℃, PCB copper thickness = 2oz. The 70mm2 copper plane reduce θ JA from 75 ℃ /W to 45 ℃ /W and increases maximum power disspation from 1.33W to 2.22W. 70mm2 copper area 30mm2 copper area Minimum copper area Figure01. Thermal Resistance θJA vs. Copper Area of ESOP Packages Figure02. Power dissipation vs. ambient temperature 7.6 VIN Decoupling To achieve the best results when using the NCT3941S/S-A, decouple the power supply with a 2.2uF capacitor. Use a high quality ceramic surface mount capacitor if possible. Surface mount components minimize lead inductance, which improves performance, and ceramic capacitors tend to have adequate high frequency response for decoupling applications. 7.7 VOUT Stability To maintain circuit stability and improve transient response over temperature and current, the NCT3941S/S-A needs a suitable output capacitor. In order to insure the circuit stability, the suitable output capacitor should be larger than 10uF. 7.8 Layout Consideration Consider the following points before starting the NCT3941S/S-A layout design. -6- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A GND Thermal pad COU T VOUT VSET CIN VIN VEN 8. 8.1 z The input bypass capacitor for VIN should be placed as close as possible to the pin with short and wide connections. z The output capacitor for VOUT should be placed close to the pin with short and wide connection in order to avoid ESR and/or ESL trace inductance. z In order to effectively remove heat from the package, properly prepare the thermal land. Apply solder directly to the package’s thermal pad. The wide traces of component and the side copper connected to the thermal land pad help to dissipate heat. The thermal land connected to the ground plane could also be used to help dissipation. ELECTRICAL CHARACTERISTIC Absolute Maximum Ratings PARAMETER RATING UNIT Power Supply Voltage -0.3 to 19V V Voltage on Other Pins -0.3 to 7V V Storage Temperature -50 to 150 °C Soldering Temperature Refer to IPC/JEDEC J-STD-020 Specification ESD Protection Human Body Mode 2 kV Machine Mode 200 V Latch-up 100 mA -7- Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A Note: Exposure to conditions beyond those listed under Absolute Maximum Ratings may adversely affect the life and reliability of the device. 8.2 Thermal Information ITEM RATING UNIT Internal Limited W 75 ℃/W RATING UNIT Operating Temperature -20 to 85 °C Junction Temperature -20 to 125 °C Supply Voltage, VCC 8 to 17.6 V Power Dissipation, PD @ TA=25℃ Package Thermal Resistance, SOP8-EP, θJA 8.3 Recommended Operating Conditions PARAMETER 8.4 Electrical Characteristics VIN=13V, VSET=2V, ENABLE=5V, CIN= 2.2uF, COUT=10uF, Ta= -20~85°C (Typical value are at Ta=25°C) PARAMETER SYM. MIN. VIN 8 TYP. MAX. UNIT 17.6 V CONDITIONS Supply Input Voltage Supply Input Voltage ENABLE / FON# Pin ENABLE / FON# Voltage High 1 V ENABLE / FON# Voltage Low ENABLE Current / FON# Pin 0.3 Bias 3 V uA ENABLE / FON# = 0V Supply Input Current Quiescent Current IQ 3 mA ENABLE = 5V, VOUT 12V, No Load Shutdown Current ISD 100 uA ENABLE = 0V Output Voltage VOUT Voltage / VSET Voltage 3.88 4 4.12 V/V Load Regulation(NOTE1) 0.5 2 % Line Regulation(NOTE1) 0.1 0.5 % -8- VIN = 12V VSET = 1 ~ 3V VSET = 3V 10mA≦IOUT≦500mA Vin = 9V to 14V Publication Date: Aug, 2010 Revision A4 NCT3941S/S-A Output Resistance 0.7 Output Leakage(NOTE2) Ω 0 1 uA 1 5.5 V IOUT = 500mA VSET = 4V ENABLE = 0V VSET Pin VSET Voltage VSET VSET pin Current 100 nA Short Circuit Current Limit Protection Output Current Limit ILIM 0.7 A Current Limit Trigger Point ITR 1.6 A Short circuit protection ISH 0.2 A Thermal Shutdown Temperature 150 °C Thermal Shutdown Hysteresis 30 °C Over Temperature Protection NOTE1 ： Slew rate will effect transient response, use TR