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PDF FAN6793 Data sheet ( Hoja de datos )
| Número de pieza | FAN6793 | |
| Descripción | (FAN6791 / FAN6793) Dual-PWM Combination Controller | |
| Fabricantes | Fairchild Semiconductor | |
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April 2009
FAN6791 / FAN6793
Highly Integrated, Dual-PWM Combination Controller
Features
High-Voltage Startup
Low Operating Current
Interleaved Stand-by PWM / Forward PWM Switching
Green Mode Stand-by PWM / Forward PWM
Linearly Decreasing Stand-by PWM Frequency to
20kHz
Remote On / Off
AC Brownout Protection
Forward PWM with Soft-Start
Frequency Hopping to Reduce EMI Emissions
Cycle-by-Cycle Current Limiting for Stand-by PWM /
Forward PWM
Leading-Edge Blanking for Stand-by PWM / Forward
PWM
Synchronized Slope Compensation for Stand-by
www.DataSheePt4WUM.co/mForward PWM
GATE Output Maximum Voltage Clamp
VDD Over-Voltage Protection (OVP)
VDD Under-Voltage Lockout (UVLO)
Internal Open-Loop Protection for Stand-by PWM /
Forward PWM
Constant Power Limit for Stand-by PWM / Forward
PWM
Description
The highly integrated FAN6791/3 dual PWM
combination controller provides several features to
enhance the performance of converters.
To minimize standby power consumption, a proprietary
green-mode function provides off-time modulation to
linearly decrease the switching frequency at light-load
conditions. To avoid acoustic-noise problems, the
minimum PWM frequency is set above 20KHz. This
green-mode function enables the power supply to meet
international power conservation requirements. With the
internal high-voltage startup circuitry, the power loss
due to bleeding resistors is also eliminated. To further
reduce power consumption, FAN6791/3 is
manufactured using the CMOS process, which allows
an operating current of only 6mA.
FAN6791/3 integrates a frequency-jittering function
internally to reduce EMI emissions of a power supply
with minimum line filters. The built-in synchronized slope
compensation achieves stable peak-current-mode
control. The proprietary internal line compensation
ensures constant output power limit.
FAN6791/3 provides many protection functions,
including brownout protection, cycle-by-cycle current
limiting, and an internal open-loop protection circuit to
ensure safety should an open-loop or output short-
circuit failure occur. PWM output is disabled until VDD
drops below the UVLO lower limit when the controller
restarts. As long as VDD exceeds ~24.5V, the internal
OVP circuit is triggered.
Applications
General-purpose switch-mode power supplies and
flyback power converters, including:
PC-ATX Power Supplies
© 2008 Fairchild Semiconductor Corporation
FAN6791 / FAN6793 • Rev. 1.0.2
www.fairchildsemi.com
1 page  
Pin Definitions
Pin # Name Description
1 HV For startup, this pin is pulled HIGH to the line input or bulk capacitor via resistors.
2 NC No connection.
3 GND Ground.
Oscillator Setting. One resistor connected between RI and ground pins determines the switching
4
RI
frequency (resistance between 12 ~ 47kΩ is recommended). The switching frequency is equal to
[1560 / RI]kHz, where RI is in kΩ. For example, if RI is equal to 24kΩ, then the switching frequency
is 65kHz.
5
FBFYB
Voltage Feedback for Flyback PWM Stage. It is internally pulled HIGH through a 6.5kΩ resistor.
An external opto-coupler from secondary feedback circuit is usually connected to this pin.
6
IFYB
PWM Current Sense for Flyback PWM Stage. The sensed voltage is used for peak-current-
mode control and cycle-by-cycle current limiting.
7
FBPWM
Voltage Feedback for Forward PWM Stage. It is internally pulled HIGH through a 6.5kΩ resistor.
An external opto-coupler from secondary feedback circuit is usually connected to this pin.
8
IPWM
PWM Current Sense for Forward PWM Stage. Via a current sense resistor, this pin provides the
control input for peak-current-mode control and cycle-by-cycle current limiting.
9 VREF Reference voltage. This pin can provide a reference voltage 5V.
PWM Soft-Start. During startup, the SS pin charges an external capacitor with a 20µA constant
10 SS current source. The voltage on FBPWM is clamped by SS during startup. In the event of a
protection condition occurring and/or forward PWM being disabled, the SS pin quickly discharges.
11
ON/OFF
PWM Remote ON/OFF. Active HIGH. The forward PWM is disabled whenever the voltage at this
pin is lower than 0.8V or the pin is open.
12 PGND Ground. The power ground.
13
OPWM
Forward PWM Gate Drive. The totem-pole output drive for the forward PWM MOSFET. This pin is
internally clamped under 16V to protect the MOSFET.
14
VDD
Power Supply. The internal protection circuit disables PWM output as long as VDD exceeds the
OVP trigger point.
www.DataShe1e5t4U.comOFYB
Flyback PWM Gate Drive. The totem-pole output drive for the forward PWM MOSFET. This pin is
internally clamped under 16V to protect the MOSFET.
16
VRMS
Line-Voltage Detection. The pin is used for line compensation, for forward, and brownout
protection.
© 2008 Fairchild Semiconductor Corporation
FAN6791 / FAN6793 • Rev. 1.0.2
5
www.fairchildsemi.com
5 Page 
Typical Characteristics
32.10
32.05
32.00
31.95
31.90
31.85
31.80
31.75
31.70
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
57.5
57.0
56.5
56.0
55.5
55.0
54.5
54.0
53.5
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 13. Rising Time tR-OPWM vs. Temperature
27.4
27.2
27.0
26.8
26.6
26.4
26.2
26.0
25.8
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 14. Falling Time tF-OPWM vs. Temperature
39
38
37
36
35
34
33
32
31
30
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 15. Rising Time tR-OFYB vs. Temperature
0.802
0.800
0.798
0.796
0.794
www.DataSheet40U.79.2com
0.790
0.788
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 16. Falling Time tF-OFYB vs. Temperature
0.667
0.666
0.665
0.664
0.663
0.662
0.661
0.660
0.659
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 17. IPWM-VLIMIT (VRMS=1V) vs. Temperature
0.815
0.810
0.805
0.800
0.795
0.790
0.785
0.780
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 18. IPWM-VLIMIT (VRMS=1.5V) vs. Temperature
0.653
0.652
0.651
0.650
0.649
0.648
0.647
0.646
0.645
0.644
0.643
-40℃ -25℃ -10℃ 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃
Figure 19. IFYB-VLIMIT (VRMS=1V) vs. Temperature
Figure 20. IFYB-VLIMIT (VRMS=1.5V)vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN6791 / FAN6793 • Rev. 1.0.2
11
www.fairchildsemi.com
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet FAN6793.PDF ] | |
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