FAN7685/FAN7686/FAN7687

Transcription

1 PC Power Supply Output Monitoring IC Features PC Power Supply Outputs Supervisory Circuitry Few External Components Over Voltage Protection for.v, 5V and 12V Outputs Under Voltage Protection for.v, 5V and 12V Outputs Over Current Protection for.v, 5V and 12V Outputs Dual Over Current Portection for 12V Outputs (FAN767) Fault Protection Output With Open Drain Output Open Drain Power Good Output 00ms Power Good Delay ms On/Off Delay 7us Debounce 2.ms to Turn Off Delay atch Function Controlled by Typical Application PC Switching Mode Power Supply Description The FAN765/FAN766/FAN767 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(), overcurrent protection (OCP), and power good signal generator to monitor and control the outputs of the switching power supply system. emote on/off() control and some precision protection features are also implemented. It directly senses all the output rails for OVP,, and OCP without external divider resistors. As for output control, power good output() and fault protection output() are included. The FAN765/FAN766/FAN767 offers a simple and cost effective solution with minimum number of external components and greatly reduces PCB board space for power supply. 1DIP 1 1SOP 1 ev Fairchild Semiconductor Corporation

2 2 Internal Block Diagrams OVP Delay 75ms S Q _O.6V Q clr Delay 2.ms clr PO EF. Start-up Vref eset Vcc Debounce ms Vcc.6V.6V 150uA Oscillator CK CK CK CK CK GND Vref VCC ISVCC12 *Iref Vcc Iref 1.2V I 6 Debounce 7us CK Debounce 7us Delay 00ms clr CK Short Detector when AC ON Block OVP Block OCP COMPs Power On eset (FAN766) FAN767 FAN765 OVP Delay 75ms Debounce 7us S Q _O.6V Q clr Delay 2.ms clr PW PO EF. Start-up Vref eset Vref Vcc Debounce ms Vcc.6V.6V 150uA Oscillator CK CK CK CK CK GND Vref Vcc Iref 1.2V I Vcc CK Debounce 7us Delay 00ms clr CK Short Detector when AC ON *Iref *Iref *Iref (7) () (9) FAN767A

3 Pin Assignments GND 2 1 VCC GND 2 1 VCC GND 2 1 VCC12 I 5 6 F A N I 5 6 F A N NC 9 I 5 6 F A N 767 FAN767A NC 7 7 ISVCC12 7 Pin Definitions Pin Number Pin Name I/O Pin Function Description 1 I Power Good Input 2 GND - Ground O Fault Protection Output, Open Drain Output I emote On/Off Control Input 5 I 12V Over Current Protection 6 I O eference Current Setting esistor NC No Connection (FAN765) 7 * I 5V Over Current Protection (FAN766) ISVCC12** I 12V-II Over Current Protection (FAN767) I 5V Over Current Protection (FAN765/7) * I.V Over Current Protection (FAN766) 9 I.V Over Current Protection (FAN765/7) * I 12V Output Over/Under Voltage Protection (FAN766) 10 I 12V Output Over/Under Voltage Protection (FAN765/7) NC* No Connection (FAN766) 11 I.V Output Over/Under Voltage Protection 12 I 5V Output Over/Under Voltage Protection 1 Vcc I Supply Voltage (FAN7675/6) VCC12** I Supply Voltage & 12V-II OV/UV Protectioin (FAN767) 1 O Power Good Output, Open Drain Output Notes : * : FAN766 Pin Definitions ** : FAN767/FAN767A Pin Definitions

4 Absolute Maximum atings Parameter Symbol Value Unit Supply Voltage VCC, VCC12 16 V Input Voltage V,,, V,,,, ISVCC12 16 Output Voltage V V 16 V Operating Temperature Topr -0 ~ 125 C Storage Temperature Tstg -55 ~ 150 C Power Dissipation PD 1 W *Note : Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. V ecommended Operating Conditions Characteristic Min. Typ. Max. Unit Supply Voltage VCC, VCC12 15 V Input Voltage Output Voltage Note 1. VCC slew rate must be less than 1V/ms. V,,, V,, - - 7,, ISVCC V V V V Output Sink Current I ma I ma Supply Voltage ising Time, See Note1 tr 1 ms Output Current for I IO(I) ua V

5 Electrical Characteristics(VCC = 5V, Ta=25 C, unless otherwise specified) Over Voltage Protection, Under Voltage Protection and Parameter Test Condition Min. Typ. Max. Unit Over Voltage Under Voltage atio of Current Sense Sink Current to Current Sense Setting Pin(I) Source Current, VCC12, VCC12 Iref.9.1. FAN767A FAN767A FAN767A () FAN767A (VCC12) FAN767A FAN767A FAN767A () FAN767A (VCC12) esistor at I=0kΩ, 0.1% esistor 7.6. Offset Voltage of OCP Comparator Voffset V=0V -5-5 mv eakage Current() IKGI V = 5V ua ow evel Output Voltage() VOI I=10mA I=0mA V and Input Voltage() V V eakage Current() IKG2 V = 5V ua ow evel Output Voltage() VO2 I=10mA V Control Input Pull-up Current I V = 0V ua igh-evel Input Voltage VIPS V ow-evel Input Voltage VIPS V Total Device Supply Current ICC V = 5V ma Switching Characteristics Debounce Time() tb ms Noise Debounce Time tb2* us Delay Time( to ) td ms Internal Delay Time td2 goes low and every time > 1.2 * : These parameters although guaranteed over the recommended operating conditions, are not 100% tested in production. V V ms goes low and td* ms everytime <1.2 off to Delay Time td tb1+1.6 tb1+2. tb1+.2 ms 5

6 Timing Chart 1) AC Input ON/OFF - Normal State VCC AC Input Enable PO OUT AC Input Disable +t d1 2) ON/OFF - Normal State t d OUT + +t d1 6

7 ) Under Voltage at Normal State atch OUT +t d1 ) Under Voltage at AC Input ON VCC AC Input Enable PO atch +t d2 OUT +t d1 7

8 5) Under Voltage at ON/OFF atch t d +t d2 OUT + +t d1 6) Over Voltage at ON/OFF atch OUT OVP +t d1

9 Typical Application Circuits FAN765 Application Circuit 12V Output S_12V 5V Coil 5V Output S_5V PWM.V Coil.V Output S_.V 5Vsb GND VCC 1 5Vsb 5 F A N I 9 7 NC FAN767 Application Circuit 12V-I Output S_12V-I 5V Coil 5V Output S_5V PWM.V Coil.V Output 12V_II Coil S_.V 12V-II Output S_12V-II ISVCC12 5Vsb ISVCC GND VCC12 1 5Vsb 5 F A N I 7 ISVCC12 9 ISVCC12 9

10 Application Information Power Good() 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 +.V, +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 +.V, +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 signal will be a low state. The AC input, power good(), remote on/off(), and +.V/+5V/+12V supply rails are shown in the below figure. T1 T5 VAC +12VDC +5VDC +.VDC 95% 10% T T2 T T6 Although there is no requirement to meet specific timing parameters, the following signal timings are recommended : -T1(Power On Time) : T1 < 500ms -T2(ise Time) : 0.1ms T2 20ms -T( Delay) : 100ms < T <500ms -T( Delay isetime) : T 10ms -T5(AC oss to old-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 FAN765/FAN766/FAN767 provide a power good() signal for the +.V, +5V and +12V supply voltage rails and a separate power good input(). An internal delay circuit is used to generate a 00ms power good delay. If voltages at (+1.2V), (+.V), (+5V), and (+12V) rise above the undervoltage threshold, the open drain power good output() will go high after a delay of 00ms. When the voltage or any of +.V, +5V, and +12V rails drops below the undervoltage threshold, the signal will be disabled immediately. Power Supply emote On/Off() and Fault Protection Output() 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() is an active-low signal that turns on all of the main power rails including the +.V, +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() also goes high. Thus, the main power rails can not deliver current and are held at 0V. When the 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 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 input signal goes from high to low or low to high, the ms debounce block will be active to avoid that a glitch on the input may disable/enable the output. When the 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.ms from to. Power should be delivered to the rails only when the signal is held at ground potential, thus the becomes a low 10

11 state after a debounce of ms. The pin can be connected to +5V(or up to +15V) through a pull-up resistor. Under Voltage Protection The FAN765/FAN766/FAN767 provide undervoltage protection() for the +.V, +5V, and +12V power rails. When an undervoltage condition appears at one of the (+.V), (+5V), or (+12V) input pins for more than 7us, the goes low and output goes high. Also, this fault condition will be latched until the 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, an internal delay time is 75ms. But at normal state an delay time is only a 7us 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 TT or CMOS logic often malfunctions under condition. Over Voltage Protection(OVP) The overvoltage protection(ovp) of the FAN765/FAN766/FAN767 monitor +.V, +5V, and +12V. When an overvoltage condition appears at one of the +.V, +5V, or +12V input pins for more than 7us, the output goes high and the goes low. Also, this fault condition will be latched until the 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 TT and CMOS circuits are very vulnerable to overvoltage, it is becoming industry standard to provide overvoltage protection on all +.V, +5V, and +12V outputs. Therefore, not only the +.V 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-OM 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 FAN765/FAN766/FAN767 provide an and OCP with a 75ms delay after is set low. The FAN765/FAN766/FAN767 provide overcurrent protection(ocp) for the.v, 5V, and 12V rails. When an overcurrent condition appears at the OCP comparator input pins for more than 7us, the output goes high and goes low. Also, this fault condition will be latched until is toggled from low to high or Vcc is removed. The resistor connected between the I pin and the GND pin will introduce an accurate IO(I) for the OCP function. Of course, a more accurate resistor tolerance will be better. The formula for choosing the I resistor is VI/IO(I). The IO(I) range is from 12.5uA to 62.5uA. Four OCP comparators and the IO(I) section are supplied by. Current drawn from the pin is less than 1mA. Following is an example on calculating OCP for the 12V rail : I V = I = V = 60kΩ I OI ( ) 20uA I OI ( ) K ( ) = ( sense) I ( OCP Trip) I ( OCP Trip) = 20u 560Ω ( 0.01Ω) = 9.2A 11

12 Mechanical Dimensions Package Dimensions in millimeters/inches 1-DIP 12

13 Mechanical Dimensions Package Dimensions in millimeters/inches 1-SOP 1

14 Ordering Information Product Number Package Operating Temperature Packing FAN765N FAN766N FAN767N FAN767AN FAN765M FAN766M FAN767M FAN767AM FAN765MX FAN766MX FAN767MX 1DIP 1SOP 1SOP -0 ~ 125 C -0 ~ 125 C -0 ~ 125 C Tube Tube Tape & eel FAN767AMX DISCAIME FAICID SEMICONDUCTO ESEVES TE IGT TO MAKE CANGES WITOUT FUTE NOTICE TO ANY PODUCTS EEIN TO IMPOVE EIABIITY, FUNCTION O DESIGN. FAICID DOES NOT ASSUME ANY IABIITY AISING OUT OF TE APPICATION O USE OF ANY PODUCT O CICUIT DESCIBED EEIN; NEITE DOES IT CONVEY ANY ICENSE UNDE ITS PATENT IGTS, NO TE IGTS OF OTES. IFE SUPPOT POICY FAICID S PODUCTS AE NOT AUTOIZED FO USE AS CITICA COMPONENTS IN IFE SUPPOT DEVICES O SYSTEMS WITOUT TE EXPESS WITTEN APPOVA OF TE PESIDENT OF FAICID SEMICONDUCTO COPOATION. As used herein: 1. ife 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. /9/0 0.0m 001 Stock#DSxxxxxxxx 200 Fairchild Semiconductor Corporation