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FS7M0880
Fairchild Power Switch(FPS)
Features
* * * * * * * * * * Precision Fixed Operating Frequency FS7M0880(66kHz) Pulse By Pulse Over Current Limiting Over Load Protection Over Voltage Protection (Min. 25V) Internal Thermal Shutdown Function Under Voltage Lockout Internal High Voltage Sense FET Latch Up Mode Soft Start
Description
The Fairchild Power Switch(FPS) product family is specially designed for an off line SMPS with minimal external components. The Fairchild Power Switch(FPS) consists of a high voltage power SenseFET and the current mode PWM controller IC. The PWM controller includes an integrated fixed oscillator, the under voltage lock out, the leading edge blanking block, the optimized gate turn-on/turn-off driver, the thermal shut down protection, the over voltage protection, the temperature compensated precision current sources for loop compensation and an fault protection circuit. Compared to just PWM controller combined MosFET or RCC switching converter solution, a Fairchild Power Switch(FPS) can reduce total component price, design size, and weight,also simultaneously increase efficiency, productivity, and system reliability. It has a simple method of application well suited for cost down design in either a flyback converter or a forward converter.
TO-3P-5L
1
1. DRAIN 2. GND 3. VCC 4. FB 5. S/S
Internal Block Diagram
#3 Vcc
UVLO Voltage Ref. Good Logic
#4 Feedback
Vcc
Vcc 1mA OSC 2.5R
Vck
5uA
#4 Drain
S Q R
Voffset LEB Sense
#5 Soft Start
5V
R
Rsense Reset 7.5V Reset
SenseFET
S Q R
#2 Source GND
Thermal Protection OVP OCL
Control IC
Rev.1.0.1
(c)2003 Fairchild Semiconductor Corporation
FS7M0880
Absolute Maximum Ratings
Parameter Drain-Gate Voltage (RGS=1M) Gate-Source (GND) Voltage Drain Current Pulsed Avalanche Current
(4) (2)
Symbol VDGR VGS IDM EAS IAS ID ID VCC,MAX VFB PD Derating TA TSTG
Value 800 30 32.0 810 15 8.0 5.6 30 -0.3 to VSD 190 1.54 -25 to +85 -55 to +150
Unit V V ADC mJ A ADC ADC V V W W/C C C
Single Pulsed Avalanche Energy (3) Continuous Drain Current (TC=25C) Continuous Drain Current (TC=100C) Maximum Supply Voltage Input Voltage Range Total Power Dissipation Operating Ambient Temperature Storage Temperature
Note: 1. Tj = 25C to 150C 2. Repetitive rating: Pulse width limited by maximum junction temperature 3. L = 24mH, VDD = 50V, RG = 25, starting Tj =25C 4. L = 13H, starting Tj = 25C
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FS7M0880
Electrical Characteristics (SFET part)
(Ta=25C unless otherwise specified) Parameter Drain-Source Breakdown Voltage Symbol BVDSS Condition VGS=0V, ID=50A VDS=Max., Rating, VGS=0V VDS=0.8Max., Rating, VGS=0V, TC=125C VGS=10V, ID=5.0A VDS=15V, ID=5.0A VGS=0V, VDS=25V, f=1MHz VDD=0.5BVDSS, ID=8.0A (MOSFET switching time are essentially independent of operating temperature) VGS=10V, ID=8.0A, VDS=0.5BVDSS (MOSFET switching time are essentially independent of operating temperature) Min. 800 1.5 Typ. 1.2 2.5 2460 210 64 95 150 60 20 70 Max. 50 200 1.5 90 200 450 150 150 nC nS pF Unit V A A S
Zero Gate Voltage Drain Current
IDSS
Static Drain-Source On Resistance (note1) RDS(ON) Forward Transconductance Input Capacitance Output Capacitance Reverse Transfer Capacitance Turn On Delay Time Rise Time Turn Off Delay Time Fall Time Total Gate Charge (Gate-Source+Gate-Drain) Gate-Source Charge Gate-Drain (Miller) Charge
Note: 1. Pulse test: Pulse width 300S, duty cycle 2% 1 2. S = --R
(note1)
gfs Ciss Coss Crss td(on) tr td(off) tf Qg Qgs Qgd
3
FS7M0880
Electrical Characteristics (CONTROL part) (Continued)
(Ta=25C unless otherwise specified) Parameter UVLO SECTION Start Threshold Voltage Stop Threshold Voltage OSCILLATOR SECTION Initial Frequency Frequency Change With Temperature Maximum Duty Cycle FEEDBACK SECTION Feedback Source Current Shutdown Delay Current SOFT START SECTION Soft Start Voltage Soft Start Current REFERENCE SECTION Output Voltage (1) Temperature Stability Peak Current Limit PROTECTION SECTION Thermal Shutdown Temperature (Tj) (1) Over Voltage Protection Voltage Over Current Protection Voltage TOTAL DEVICE SECTION Start Up Current Operating Supply Current (Control Part Only) Shutdown Feedback Voltage ISTART IOP Iop(lat) VSD VCC=14V Ta=25C After latch, Vcc=Vstop-0.1V 150 6.9 40 8 250 7.5 80 12 350 8.1 uA mA uA V TSD VOVP VOCP 140 25 1.05 28 1.10 31 1.15 C V V
(1)(2) (2)
Symbol VSTART VSTOP FOSC F/T Dmax IFB Idelay VSS ISS Vref Vref/T IOVER
Condition After turn on -25C Ta +85C Ta=25C, 0V Vfb 3V Ta=25C, 5V Vfb VSD VFB =2V Sync & S/S=GND Ta=25C -25C Ta +85C Max. inductor current
Min. 14 8 60 45 0.7 4.0 4.7 0.8 4.80 4.40
Typ. 15 9 66 5 50 0.9 5.0 5.0 1.0 5.00 0.3 5.00
Max. 16 10 72 10 55 1.1 6.0 5.3 1.2 5.20 0.6 5.60
Unit V V kHz % % mA A V mA V mV/C A
CURRENT LIMIT (SELT-PROTECTION)SECTION
Note: 1. These parameters, although guaranteed, are not 100% tested in production 2. These parameters, although guaranteed, are tested in EDS (wafer test) process
4
FS7M0880
Block Diagram
It can be divided into several large, functional sections: under voltage lockout circuitry (UVLO); reference voltage; oscillator (OSC); pulse width modulation (PWM) block; protection circuits; and gate driving circuits.
described in Fig 2. Although VCC only needs to be set above 9V during operation, it should be set such that OVP does not execute during an overload condition. For a full load, about 18~20V is appropriate for the VCC voltage and for no load, about 13~14V.
Start Up
Input voltage range: 85 ~ 265 V (AC) When Vac is minimum and it is started by the DC Link bulk capacitor, the starting resistance is calculated as follows:
85 2 - 15 R start = -------------------------- = 1.3M 80A
Protection
The FPS has several self-protection circuits, which can operate without additional external components, thereby acquiring reliability without increase in cost. After a protection circuit comes on, it can completely stop the SMPS until the cutoff AC power is reconnected (Latch Mode Protection) or it can make the SMPS operate above the UVLO by unlatching the control voltage below the ULVO (Auto Restart Mode Protection).
When Vac is maximum and it is started by the DC Link Bulk capacitor, the power loss is calculated as follows:
( 265 2 - 15 ) Ploss = ------------------------------------- = 0.1 ( W ) 1.3M
2
Va 265V 85V
UVLO
When it is started by the one-phase of the AC-Lines and Vac is minimum, the starting resistance is calculated as follows:
Figure 1. Detail of the undervoltage lockout (UVLO) circuitry in a Fairchild Power Switch. The gate operating circuit holds in a low state during UVL thereby maintaining the SenseFET at turnoff.
R
2 * 85 2 - 15 = --------------------------------------- / ( 80A ) Start 2 = 38M
These two operations are user-command operations, so the user can select the operation from the IC or by carefully controlling circuit constants. The operation and applications for each protection are described below.
Icc [mA]
When it is started bythe one-phase of the AC_Line and Vac is maximum, the power loss is calculated as follows:
2 1 ------ ( Vp sin t - 15 ) dt 2 o
Va ( rms ) =
20
= 177V ( Vp = 265 2 ) Va ( rms ) 2 ( 177 ) 2 = -------------------------- = ----------------P loss Rstart 38M = 82 ( mW )
7
Power On Reset Range
0.1 6V 9V 15V Vz
Vcc [V]
The starting current across the starting resistor charges the SPS VCC capacitor. When the VCC becomes greater than the starting voltage, the SPS starts to switch the built-in MOSFET. Once it starts, the current in the SPS control IC abruptly is increased to 7mA, makes it difficult to operate with the current through the starting resistor. Therefore, after it starts, the auxiliary winding of the transformer supplies most of the power to SPS. It is best to use an appropriate size VCC power capacitor, generally about 33F, because if it is too large, the starting time can be delayed. This operation is
Fig 2
< Start-up Waveform >
Figure 2. Start-up Waveform Over Load Protection
In abnormal status of SMPS over load is distinguished from load short. This happens when a load exceeds a pre-set load during normal operation. That is, the FPS overload protection circuit stops the FPS if an instantaneous load increases and becomes greater than 50W during normal operation, when the maximum SMPS output had been pre-set to 30W. In this type of protection, the protection 5
FS7M0880
4uA Vo V fb #4 Cd V z = 3 .9 V K A 431 7 .5 V C fb D1
0 .9 m A
D2 V fb *
7.5V
3 .9V 3 .0V 0V t t1 t2 t3 4 u A = C fb * 0 .9 V / t 2 4 u A = C d * 3 .6 V / t3
T im e C o n s ta n t = 3.5R *C fb
S h u td o w n
Figure 3. SPS Delayed Shutdown
circuit can perform undesired operations even during transient state, which lasts until normal operation. As a measure against this problem, this protection circuit in the SPS operates after a specified period to determine whether the condition is a transient or an overload. This is done to prevent protection circuit operation during a transient state, which returns normal after a specified period. This operation is described as follows. Because the FPS uses the current control mode, it cannot flow current over the set maximum current, and therefore the maximum input power is restricted at the characteristic voltage. Therefore, if the output consumes beyond this maximum power, VO, shown in the figure below, becomes less than the set voltage and only the provided minimum current can flow through KA431. As a result, the secondary current of the photocoupler becomes almost zero. If all the SPS's 0.9mA current source flows through the internal resistor (2.5R + R *=* 3k), Vfb becomes approximately 3V, and the 4A current starts to charge Cfb. Because the photocoupler secondary current is almost zero, Vfb continues to increase until it reaches 7.5V, at which time the SPS shutsdown. The delay time to shutdown is the time required to charge Cfb to 4.5V with 4A and can be easily set. When Cfb is 10nF(103), t2 is approximately 11.2mS and when 0.1F(104) approximately 120ms. With this amount of the SPS does not shutdown for most transient states. Just increasing Cfb to obtain a longer delay time can become a problem, because Cfb is an important parameter for determining the response speed (Dynamic Response) of the SMPS. Similarly, Vfb exceeds 3V and the 4uA current starts to charge the Cfb. At this time, Vfb continues to increase until it becomes 7.5V, at which time a resistor could be added between the F/B pin and GND to lengthen the time to 6
SPS shutdown. If a part of delay current go through the added resistor, the time to shutdown can be lengthened. In our test the delay shutdown time with Cfb(473) and resistor (3.9M) is about two times longer than with only Cfb(473). When Vfb is 7.5V, the current flowing through this 3.9m resistor is approximately 1.9A. To obtain the same results, if a zener diode (about 3.9 ~ 4.7V) in series connection with a capacitor is parallel-connected to Cfb, as depicted in Fig 3., the desired shutdown delay time could be obtained according to the size of the capacitor.
Over voltage Protection Circuit
The FPS has a self-protection feature against malfunctions, such as feedback circuit open or short-circuit. When the feedback terminal short circuits as seen from the primary side, the feedback terminal voltage becomes zero, and switching cannot start as a result. If the feedback terminal opens, then the protection circuit initiates as in the overload protection circuit. If the feedback terminal looks open due to a malfunction in the secondary side feedback circuit or a non-solder, the primary side continues to switch with the set maximum current until the protection circuit come on; therefore, it is normal for the secondary side voltage to become much greater than the rated voltage. If there was no protection circuit guarding against such conditions, the fuse can blow or, even more serious, a fire can start. Even if it does not lead such dire circumstances, the IC connected to the secondary side without a regulator could be destroyed (especially the digital IC such as TTL IC etc.) For such instances, time, the over voltage protection circuit (protection against feedback circuit abnormalities) starts to operate in the SPS. In such circumstances, the output voltage, which increases tremendously, is made proportional
FS7M0880
to the SPS VCC voltage. If VCC exceeds 24 V, the SPS IC starts the protection circuit. Therefore, VCC should be appropriately kept below 24V during normal operation.
OCP (Over Current Protection)
OCP Operating
entire circuit is seriously stressed. Use of a soft start function avoids such stresses. Figure 6 shows how to implement a soft start for a Fairchild Power Switch(FPS). At turn on, the soft start capacitor on pin 5 of the Fairchild Power Switch(FPS) starts to charge through the 1mA current source. When the voltage across CS reaches 3V, diode DS turns off. No more current flows to it from the 1mA current source. Cs then continues to charge to 5V through the 20k resistor.
SQ R
200ns 100ns delay
Latch signal
Rsense OCP time R C OCP Level
10V 4uA 0.9mA
Fairchild Power Switch(FPS)
PWM Comparator 5V
Minimum Turn-on Time
20K
Fiqure 5. OCP Function & Block
#4 #5
The FPS has various built-in, basic protection features. They are the UVLO (Under Voltage Lock Out), OLP (Over Load Protection) and OCP (Over Current Protection). However, if a secondary side diode short or load short occur due to a worst case condition, such as a maximum input voltage putting a large strain on the device, another external component may need to be added. By adding these requirements in the FPS, superior reliability and advantageous cost can be achieved. When gate on signal of the SenseFet is received, simultaneously the OCP block senses Ipeak through the sense resistor for 1us. After the OCP block has turned on, the voltage across the resistor is compared to the pre-set voltage in the comparator, and, if it takes longer than 200ns within the allowed comparison time of 1us, then the comparator produces a high signal, which latches the OCP. fig 4. shows the OCP latch waveform. When there is a diode short/load short, the SPS turns on for the minimum turn-on time. If the instantaneous current is of the form shown in fig 4., the OCP block opens a 1us window to compare the voltage proportional to the current across the resistor with the reference voltage and latches. Here, the 100ns delay after the 200ns is the delay time to SenseFET gate off and is generated from the comparison of the voltage across the sense resistor.
CS
Figure 6. Soft Start Circuit.
Note that when the voltage across CS exceeds 3V, The voltage at the comparator's inverting terminal no longer follows the voltage across CS. Instead, it follows the output voltage feedback signal. In shutdown or protection circuit operation, capacitor CS is discharged, to enable it to charge from 0V at restart.
Soft start operation
Normally, the SMPS output voltage increases from start up with a fixed time constant. This is due to the capacitive component of the load. At start up, therefore, the feedback signal applied to the PWM comparator's inverting input reaches its maximum value (1V), This is because the feedback loop is effectively open. Also at this time, the drain current is at its peak value (Ipeak) and maximum allowable power is being delivered to the secondary load. With that said, note that when the SMPS pushes maximum power to the secondary side for this initial fixed time, the
7
FS7M0880
3. Application Note using the SPS
-Flyback Application (100W)
HOT
NTC Bridge Diode 47nF /630V 220uF /400V MBRF2060CT 5M UF4007 1K 2200uF /50V 0.45uF /275Vac UF4004 Line Filter 3 1 Vcc Drain 5 KA7M0880 GND 2 FB 4 10 4.7nF 1.2k 4.7nF S/S 4.7nF 4.7nF 0.45uF /275Vac FUSE: 250V2A 3.3k KA431 2k 2k Q817A 7.6k 2200uF /50V 30uH 47k /2W
12V / 9A DC OUTPUT
0.1uF
47uF /50V
1uF /50V
22nF 10nF Q817A
185VAC-265VAC
PRIMARY GND
Transformer Specification
2. Winding Specification
No. NP/2 N+12V NB NP/2 PIN(S F) 13 12 13 87 34 WIRE 0.4 x 1 14mm x 1 0.3 x 1 0.4 x 1 TURNS 42 8 9 42 WINDING METHOD SOLENOID WINDING COPPER WINDING SOLENOID WINDING SOLENOID WINDING
INSULATION : POLYESTER TAPE t = 0.050mm, 1Layer INSULATION : POLYESTER TAPE t = 0.050mm, 3Layer INSULATION : POLYESTER TAPE t = 0.050mm, 1Layer OUTER INSULATION : POLYESTER TAPE t = 0.050mm, 3Layer
3. Electical Characteristic
CLOSURE INDUCTANCE LEAKAGE L PIN 1-4 1-4 SPEC. 700uH 10% 10uH MAX. REMARKS 1kHz, 1V 2nd ALL SHORT
4. Core & Bobbin
CORE : EER 4042 BOBBIN : EER4042
8
FS7M0880
-Forward Application (250W)
223 56K 56K /2W T1 T13,14 UF4007 Line Inductor
/630V /2W NTC Line FUSE Inductor
+ 12V / 10A
102 472 /275V 0.47uF /275V 220k 470uF /200V /1W UF4007
T3 10
2200uF
2200uF
472 /275V 33k /0.5W 33k /0.5W UF4007
220k /1W
470uF T8,9 /200V
S30SC4M
L4
+ 5V / 26A
2.2k UF4004 T6 10 3300uF 1000uF 2.2k
Vcc
Drain
T10,11,12 T7 5.6k 1k
SPS
GN D
123 33uF /35V 1uF /50V 333
S.S.
F.B.
Q817
820
104 Q817 103 103 KA431
Transformer Specification
2. Winding Specification
No. NP/2 N+5V N+12V NP/2 NVCC PIN(S F) 13 8, 9 10, 11, 12 13, 14 9 13 76 WIRE 0.65 x 1 14mm x 1 0.65 x 4 0.65 x 1 0.65 x 1 TURNS 50T 4T 5T 50T 6T WINDING METHOD SOLENOID WINDING COPPER WINDING SOLENOID WINDING SOLENOID WINDING SOLENOID WINDING
3. Electical Characteristic
CLOSURE INDUCTANCE LEAKAGE L PIN 1-3 1-3
4. Secondary Inductor(L2) Specipication
Core : Power Core 27 16 Grade 5V : 12T (1 x 2) 10V : 27T (1.2 x 1)
9
FS7M0880
Package Dimensions
TO-3P-5L
10
FS7M0880
Package Dimensions (Continued)
TO-3P-5L(Forming)
11
FS7M0880
Ordering Information
Product Number FS7M0880TU FS7M0880YDTU
TU : Non Forming Type YDTU : Forming type
Package TO-3P-5L TO-3P-5L(Forming)
Rating 800V, 8A
Fosc 67kHz
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.
www.fairchildsemi.com 8/25/03 0.0m 001 Stock#DSxxxxxxxx 2003 Fairchild Semiconductor Corporation
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.

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