www.fairchildsemi.com FAN7685/FAN7686/FAN7687 PC Power Supply Output Monitoring IC Features Description • • • • • • • • • • • • • The FAN7685/FAN7686/FAN7687 is a complete output supervisory circuitry intended for use in the secondary side of the switched mode power supply. It provides overvoltage protection (OVP), undervoltage protection(UVP), overcurrent protection (OCP), and power good signal generator to monitor and control the outputs of the switching power supply system. Remote on/off(PSON) control and some precision protection features are also implemented. It directly senses all the output rails for OVP, UVP, and OCP without external divider resistors. As for output control, power good output(PGO) and fault protection output(FPO) are included. The FAN7685/FAN7686/FAN7687 offers a simple and cost effective solution with minimum number of external components and greatly reduces PCB board space for power supply. PC Power Supply Outputs Supervisory Circuitry Few External Components Over Voltage Protection for 3.3V, 5V and 12V Outputs Under Voltage Protection for 3.3V, 5V and 12V Outputs Over Current Protection for 3.3V, 5V and 12V Outputs Dual Over Current Portection for 12V Outputs(FAN7687) Fault Protection Output With Open Drain Output Open Drain Power Good Output 300ms Power Good Delay 38ms PSON On/Off Delay 73us Debounce 2.3ms PSON to FPO Turn Off Delay Latch Function Controlled by PSON Typical Application 14DIP • PC Switching Mode Power Supply 1 14SOP 1 Rev. 1.1.0 ©2004 Fairchild Semiconductor Corporation FAN7685/FAN7686/FAN7687 Internal Block Diagrams Vcc Vcc 13 Start-up PSON 3.6V REF. clr Delay 2.3ms Vref Oscillator POR VS12 10 CLK CLK Reset (9) R UVP VS5 12 L L R L H VS33 11 Delay 75ms Debounce 73us L S 3 FPO H FPO L Q L CLK CLK L L R PWR clr L L PGI_O R Vcc 150uA 3.6V OVP L PSON L L L 4 PSON CLK R Vref L Debounce 38ms L 3.6V H Q IS33 9 2 L L H (8) 14 PGO L IS5 8 L (7) GND H UVP H IS12 5 R L L Vcc H Iref Short Detector H when AC ON L 8*Iref 8*Iref 8*Iref H L CLK Debounce 73us H Delay clr 300ms Vref 1.2V FAN7685 (FAN7686) CLK PSON VCC12 13 6 1 RI PGI Vcc Start-up PSON 3.6V REF. clr Delay 2.3ms Vref Oscillator POR Power On Reset CLK CLK Reset R UVP Block UVP L L R L H VS12 10 Delay 75ms L L R Debounce 73us L S Q 3 FPO H FPO L CLK CLK clr VS5 12 L VS33 11 OVP Block L PGI_O R Vcc 150uA 3.6V OVP L PSON L Debounce 38ms R L L 4 PSON CLK 3.6V H IS33 9 Q L 2 GND L L 14 PGO IS5 8 H OCP COMPs IS12 5 H Iref ISVCC12 7 L L 1.2V 8*Iref L PSON 6 1 RI PGI R H L CLK Debounce 73us H Short Detector when AC ON H H H Delay clr 300ms CLK Vref 2 L UVP Vcc FAN7687 FAN7687A FAN7685/FAN7686/FAN7687 Pin Assignments PGI 1 14 PGO GND 2 RI 6 GND 2 12 VS5 FPO 3 11 VS33 PSON 4 10 VS12 IS12 5 9 IS33 NC 7 RI 6 8 IS5 IS5 7 14 PGO PGI 1 14 PGO 13 VCC GND 2 13 VCC12 12 VS5 FPO 3 11 VS33 PSON 4 10 NC IS12 5 9 VS12 RI 6 8 IS33 F A N 7687 FAN7687A IS12 5 13 VCC F A N 7 686 PSON 4 F A N 7 685 FPO 3 PGI 1 ISVCC12 7 12 VS5 11 VS33 10 VS12 9 IS33 8 IS5 Pin Definitions Pin Number Pin Name I/O 1 PGI I Power Good Input 2 GND - Ground 3 FPO O Fault Protection Output, Open Drain Output 4 PSON I Remote On/Off Control Input 5 IS12 I 12V Over Current Protection 6 RI O Reference Current Setting Resistor No Connection(FAN7685) NC 7 8 9 10 Pin Function Description IS5* I 5V Over Current Protection(FAN7686) ISVCC12** I 12V-II Over Current Protection(FAN7687) IS5 I 5V Over Current Protection(FAN7685/7) IS33* I 3.3V Over Current Protection(FAN7686) IS33 I 3.3V Over Current Protection(FAN7685/7) VS12* I 12V Output Over/Under Voltage Protection(FAN7686) VS12 I 12V Output Over/Under Voltage Protection(FAN7685/7) No Connection(FAN7686) NC* 11 VS33 I 3.3V Output Over/Under Voltage Protection 12 VS5 I 5V Output Over/Under Voltage Protection Vcc I Supply Voltage(FAN7675/6) VCC12** I Supply Voltage & 12V-II OV/UV Protectioin(FAN7687) PGO O Power Good Output, Open Drain Output 13 14 Notes : * : FAN7686 Pin Definitions ** : FAN7687/FAN7687A Pin Definitions 3 FAN7685/FAN7686/FAN7687 Absolute Maximum Ratings Parameter Symbol Value Unit VCC, VCC12 16 V VPSON, VS5, VS33, VPGI, IS5, IS33 8 VS12, IS12, ISVCC12 16 VPGO 8 VFPO 16 Operating Temperature Topr -40 ~ 125 °C Storage Temperature Tstg -55 ~ 150 °C Power Dissipation PD 1 W Supply Voltage Input Voltage Output Voltage V V *Note : Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. Recommended Operating Conditions Characteristic Supply Voltage Input Voltage Output Voltage Output Sink Current Supply Voltage Rising Time, See Note1 Output Current for RI Note 1. VCC slew rate must be less than 14V/ms. 4 Min. Typ. Max. Unit 15 V VCC, VCC12 4 VPSON , VS5, VS33, VPGI, IS5, IS33 - - 7 VS12, IS12, ISVCC12 - - 15 VPGO - - 7 V VFPO - - 15 V IFPO - - 30 mA IPGO - - 10 mA tr 1 IO(RI) 12.5 V ms - 62.5 uA FAN7685/FAN7686/FAN7687 Electrical Characteristics(VCC = 5V, Ta=25°C, unless otherwise specified) Over Voltage Protection, Under Voltage Protection and FPO Parameter Test Condition VS33 Over Voltage Threshold VS5 VS12, VCC12 VS33 Under Voltage Threshold VS5 VS12, VCC12 Ratio of Current Sense Sink Current to Current Sense Setting Pin(RI) Source Current Iref FAN7687A Min. Typ. Max. 3.9 4.1 4.3 3.77 5.8 FAN7687A FAN7687A(VS12) 13.71 FAN7687A(VCC12) 13.42 2.55 FAN7687A 2.88 FAN7687A 4.37 4.1 8.8 FAN7687A(VS12) FAN7687A(VCC12) 4.06 6.1 6.4 13.8 14.3 5.71 13.3 Unit 6.16 V 14.79 14.5 2.69 2.83 3.02 4.3 4.5 4.58 9.3 V 9.8 10.5 11.0 10.21 10.71 Resistor at RI=30kΩ, 0.1% Resistor 7.6 8 8.4 Offset Voltage of OCP Comparator Voffset VPSON=0V -5 - 5 mV Leakage Current(FPO) ILKGI VFPO = 5V - - 5 uA Low Level Output Voltage(FPO) VOLI IFPO=10mA - - 0.3 IFPO=30mA - - 0.7 1.16 1.20 1.24 V V PGI and PGO Input Threshold Voltage(PGI) VPGI Leakage Current(PGO) ILKG2 VPGO = 5V - - 5 uA Low Level Output Voltage(PGO) VOL2 IPGO=10mA - - 0.4 V Input Pull-up Current IPSON VPSON = 0V - 150 - uA High-Level Input Voltage VIHPS 2.4 - - V Low-Level Input Voltage VILPS - - 1.2 V - - 1 mA 25 38 51 ms PSON Control Total Device Supply Current ICC VPSON = 5V Switching Characteristics Debounce Time(PSON) Noise Debounce Time PGO Delay Time(PGI to PGO) tb1 tb2* td1 73 100 us 300 410 ms td2 FPO goes low and every time PGI > 1.2 51 75 102 ms td4* FPO goes low and everytime PGI<1.2 200 300 410 ms Internal UVP Delay Time PSON off to FPO Delay Time 50 200 td3 tb1+1.6 tb1+2.3 tb1+3.2 ms * : These parameters although guaranteed over the recommended operating conditions, are not 100% tested in production. 5 FAN7685/FAN7686/FAN7687 Timing Chart 1) AC Input ON/OFF - Normal State VCC AC Input Enable POR PSON FPO tb1 PGI AC Input Disable UVP Threshold OUT tb2+td1 PGO 2) PSON ON/OFF - Normal State PSON FPO td3 tb1 PGI UVP Threshold OUT tb1+tb2 PGO 6 tb2+td1 FAN7685/FAN7686/FAN7687 3) Under Voltage at Normal State PSON Latch FPO tb1 tb2 PGI UVP Threshold UVP Threshold OUT tb2+td1 PGO 4) Under Voltage at AC Input ON VCC AC Input Enable POR Latch PSON FPO PGI tb1 tb2+td2 PGI Threshold UVP Threshold OUT PGO tb2+td1 7 FAN7685/FAN7686/FAN7687 5) Under Voltage at PSON ON/OFF Latch PSON FPO td3 tb1 tb2+td2 PGI PGI Threshold UVP Threshold OUT tb1+tb2 tb2+td1 PGO 6) Over Voltage at PSON ON/OFF PSON FPO Latch tb2 PGI OUT PGO 8 tb1 UVP Threshold OVP Threshold tb2+td1 FAN7685/FAN7686/FAN7687 Typical Application Circuits FAN7685 Application Circuit 12V Output RS_12V RIS12 5V Output RS_5V RIS5 PWM VS12 IS12 5V Coil VS5 IS5 3.3V Coil 3.3V Output RS_3.3V RIS33 VS33 IS33 5Vsb 1 PGI PSON FPO 4 PSON 5 IS12 5Vsb VCC 13 F A N 7685 3 PGO PGO 14 2 GND VS5 VS5 12 VS33 11 VS33 VS12 10 VS12 6 RI IS33 9 7 NC IS5 8 FAN7687 Application Circuit 12V-I Output RS_12V-I RIS12 VS12 IS12 5V Coil 5V Output RS_5V RIS5 PWM VS5 IS5 3.3V Coil 3.3V Output RIS33 RS_3.3V VS33 IS33 12V_II Coil 12V-II Output RS_12V-II RISVCC12 ISVCC12 5Vsb 1 PGI PGO 14 2 GND FPO PSON 4 PSON IS12 5 IS12 5Vsb VCC12 13 F A N 7687 3 PGO 6 RI 7 ISVCC12 VS5 12 VS5 VS33 11 VS33 VS12 10 VS12 IS33 9 IS33 IS5 8 IS5 ISVCC12 9 FAN7685/FAN7686/FAN7687 Application Information Power Good(PGO) and Power Good Delay A PC power supply is commonly designed to provide the motherboard with a power good signal, which is defined by the computer manufacturers. If the +3.3V, +5V, and +12V outputs are above the undervoltage threshold limit, the PC power supply makes the power good signal high. At this time the power supply should be able to provide enough power to assure continuous operation within the specification. Conversely, when one of the +3.3V, +5V, or +12V outputs falls below the undervoltage threshold or rises above the overvoltage threshold, or when main power has been turned off for a sufficiently long time so that power supply operation is no longer assured, a PGO signal will be a low state. The AC input, power good(PGO), remote on/off(PSON), and +3.3V/+5V/+12V supply rails are shown in the below figure. T1 T5 VAC PSON +12VDC +5VDC +3.3VDC PGO 95% 10% T3 T2 T4 T6 Although there is no requirement to meet specific timing parameters, the following signal timings are recommended : -T1(Power On Time) : T1 < 500ms -T2(Rise Time) : 0.1ms ≤ T2 ≤ 20ms -T3(PGO Delay) : 100ms < T3 <500ms -T4(PGO Delay Risetime) : T4 ≤ 10ms -T5(AC Loss to PGO Hold-Up Time) : T5 ≥ 16ms -T6(Power Down Warning) : T6 ≥ 1ms Furthermore, motherboards should be designed to comply with the above recommended timing range. If timings other than these are implemented or required, that information should be clearly specified. The FAN7685/FAN7686/FAN7687 provide a power good(PGO) signal for the +3.3V, +5V and +12V supply voltage rails and a separate power good input(PGI). An internal delay circuit is used to generate a 300ms power good delay. If voltages at PGI(+1.2V), VS33(+3.3V), VS5(+5V), and VS12(+12V) rise above the undervoltage threshold, the open drain power good output(PGO) will go high after a delay of 300ms. When the PGI voltage or any of +3.3V, +5V, and +12V rails drops below the undervoltage threshold, the PGO signal will be disabled immediately. Power Supply Remote On/Off(PSON) and Fault Protection Output(FPO) Since the latest personal computer generation focuses on easy turn on and power saving functions, a PC power supply will require two characteristics. One is a dc power supply remote on/off function; the other is standby power to achieve very low power consumption of the PC power supply. Thus, the main power needs to be shut down. The power supply remote on/off(PSON) is an active-low signal that turns on all of the main power rails including the +3.3V, +5V, and +12V power rails. When this signal is held high by the PC motherboard or left open circuited, the signal of the fault protect output(FPO) also goes high. Thus, the main power rails can not deliver current and are held at 0V. When the FPO signal is held high due to a fault condition, the fault status will be latched and the outputs of the main power rails can not deliver current and are held at 0V. Toggling the PSON input signal from low to high will reset the fault protection latch. During this fault condition only the standby power is not affected. When the PSON input signal goes from high to low or low to high, the 38ms debounce block will be active to avoid that a glitch on the PSON input may disable/enable the FPO output. When the PSON is set low, the undervoltage function is disabled for 75ms to avoid turn-on failure. At turn-off, there is an additional delay of 2.3ms from PSON to FPO. Power should be delivered to the rails only when the PSON signal is held at ground potential, thus the FPO becomes a low 10 FAN7685/FAN7686/FAN7687 state after a debounce of 38ms. The FPO pin can be connected to +5V(or up to +15V) through a pull-up resistor. Under Voltage Protection The FAN7685/FAN7686/FAN7687 provide undervoltage protection(UVP) for the +3.3V, +5V, and +12V power rails. When an undervoltage condition appears at one of the VS33(+3.3V), VS5(+5V), or VS12(+12V) input pins for more than 73us, the PGO goes low and FPO output goes high. Also, this fault condition will be latched until the PSON is toggled from low to high or the Vcc falls below a minimum operating voltage. When the power supply is turned on by the AC input or PSON, an internal UVP delay time is 75ms. But at normal state an UVP delay time is only a 73us debounce time. The need for undervoltage protection is often overlooked in off-line switching power supply system design. But it is very important in battery powered or hand-held equipment since the TTL or CMOS logic often malfunctions under UVP condition. Over Voltage Protection(OVP) The overvoltage protection(OVP) of the FAN7685/FAN7686/FAN7687 monitor +3.3V, +5V, and +12V. When an overvoltage condition appears at one of the +3.3V, +5V, or +12V input pins for more than 73us, the FPO output goes high and the PGO goes low. Also, this fault condition will be latched until the PSON is toggled from low to high or Vcc drops below a minimum operating voltage. During overvoltage condition, most power supplies have the potential to deliver higher output voltages than those normally specified or required. In unprotected equipment, it is possible for output voltages to be high enough to cause internal or external damage to the system. To protect the system under these abnormal conditions, it is common practice to provide overvoltage protection within the power supply. Because TTL and CMOS circuits are very vulnerable to overvoltage, it is becoming industry standard to provide overvoltage protection on all +3.3V, +5V, and +12V outputs. Therefore, not only the +3.3V and +5V rails for the logic circuits on the motherboard need to be protected, but also the +12V peripheral devices such as the hard disk, flopply disk, and CD-ROM players etc., need to be protected. Over Current Protection In bridge or forward type, off-line switching power supplies, usually designed from medium to large power, the overload protection design needs to be very precise. Most of these types of power supplies are sensing the output current for an overload condition. The trigger point needs to be set higher than the maximum load in order to prevent false turn-on. During safety testing the power supply might have tied the output voltage direct to ground. If this happens during the nomal operating, this is called a short-circuit or over current condition. When it happens before the power supply turns on, this is called a short-circuit power supply turn-on. It can happen during the design period, in the production line, at quality control inspection or at the end user. The FAN7685/FAN7686/FAN7687 provide an UVP and OCP with a 75ms delay after PSON is set low. The FAN7685/FAN7686/FAN7687 provide overcurrent protection(OCP) for the 3.3V, 5V, and 12V rails. When an overcurrent condition appears at the OCP comparator input pins for more than 73us, the FPO output goes high and PGO goes low. Also, this fault condition will be latched until PSON is toggled from low to high or Vcc is removed. The resistor connected between the RI pin and the GND pin will introduce an accurate IO(RI) for the OCP function. Of course, a more accurate resistor tolerance will be better. The formula for choosing the RI resistor is VRI/IO(RI). The IO(RI) range is from 12.5uA to 62.5uA. Four OCP comparators and the IO(RI) section are supplied by VS12. Current drawn from the VS12pin is less than 1mA. Following is an example on calculating OCP for the 12V rail : V RI 1.2V- = 60kΩ RI = ------------- = ------------I O ( RI ) 20uA I O ( RI ) × K × R ( IS12 ) = R ( sense ) × I ( OCP – Trip ) I ( OCP – Trip ) = 20u × 8 × 560Ω ⁄ ( 0.01Ω ) = 9.2A 11 FAN7685/FAN7686/FAN7687 Mechanical Dimensions Package Dimensions in millimeters/inches 14-DIP 12 FAN7685/FAN7686/FAN7687 Mechanical Dimensions Package Dimensions in millimeters/inches 14-SOP 13 FAN7685/FAN7686/FAN7687 Ordering Information Product Number Package Operating Temperature Packing 14DIP -40 ~ 125°C Tube 14SOP -40 ~ 125°C Tube 14SOP -40 ~ 125°C Tape & Reel FAN7685N FAN7686N FAN7687N FAN7687AN FAN7685M FAN7686M FAN7687M FAN7687AM FAN7685MX FAN7686MX FAN7687MX FAN7687AMX DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com 3/9/04 0.0m 001 Stock#DSxxxxxxxx 2004 Fairchild Semiconductor Corporation