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PDF SG6905SY Data sheet ( Hoja de datos )
| Número de pieza | SG6905SY | |
| Descripción | Green mode PFC/Flyback-PWM Controller | |
| Fabricantes | Fairchild Semiconductor | |
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October 2008
SG6905
Green Mode PFC/Flyback-PWM Controller
Features
Interleaved PFC/PWM Switching
Green Mode PWM Operation
Low Startup and Operating Current
Innovative Switching-Charge Multiplier-Divider
Average-Current-Mode Control for PFC
PFC Over-Voltage and Under-Voltage Protections
PFC Remote On/Off Control
PFC and PWM Feedback Open-Loop Protection
Cycle-by-Cycle Current Limiting for PFC/PWM
Slope Compensation for PWM
Constant Power Limit for PWM
Power-On Sequence Control
Brownout Protection
Over-Temperature Protection
Applications
Switching Power Suppliers with Active PFC
High-Power Adaptors
LCD TV Applications
Description
The highly integrated SG6905 is specially designed for
power supplies consisting of boost PFC and flyback
PWM. It requires very few external components to
achieve green-mode operation and versatile
protections. It is available in 20-pin SOP package.
The proprietary interleave-switching feature
synchronizes the PFC and PWM stages and reduces
switching noise. At light loads, the switching frequency
is continuously decreased to reduce power
consumption.
For PFC stage, the proprietary multi-vector control
scheme provides a fast transient response in a low-
bandwidth PFC loop, in which the overshoot and
undershoot of the PFC voltage are clamped. If the
feedback loop is broken, the SG6905 shuts off PFC to
prevent extra-high voltage on output.
For the flyback PWM, the synchronized slope
compensation ensures the stability of the current loop
under continuous-conduction-mode operation. Built-in
line-voltage compensation maintains constant output-
power limit. Hiccup operation during output overloading
is also guaranteed.
During startup, the RDY (ready) is pulled low until the
PFC output voltage reaches the setting level. This
signal can be used to control the second power stage
for proper power-on sequence.
In addition, SG6905 provides complete protection
functions, such as brownout protection and RI pin
open/short.
Ordering Information
Part Number
SG6905SY
Operating
Temperature Range
Package
-40°C to +105°C 20-pin Small Outline Package (SOP)
Eco Status
Green
Packing
Method
Tape & Reel
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2007 Fairchild Semiconductor Corporation
SG6905 • Rev. 1.1.2
www.fairchildsemi.com
1 page  
Pin Definitions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
VRMS
RI
OTP
IEA
IPFC
IMP
ISENSE
FBPWM
IPWM
AGND
SS
OPWM
GND
OPFC
VDD
RDY
PFC_ON
FBPFC
VEA
IAC
Description
Line Voltage Detection. The pin is used for PFC multiplier, brownout protection. For brownout
protection, the controller is disabled after a delay time when the VRMS voltage drops below a
threshold.
Reference Setting. One resistor connected between RI and ground determines the switching
frequency. 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.
Over-Temperature Protection. This pin supplies an over-temperature-protection signal. A
constant current is output from this pin. An external NTC thermistor must be connected from
this pin to ground. The impedance of the NTC thermistor decreases whenever the temperature
increases. Once the voltage of the OTP pin drops below the OTP threshold, the SG6905 is
disabled.
Output for PFC Current Amplifier. This is the output of the PFC current amplifier. The signal
from this pin is compared with an internal saw-tooth and hence determines the pulse width for
PFC gate drive.
Inverting Input for PFC Current Amplifier. The inverting input of the PFC current amplifier.
Proper external compensation circuits result in excellent input power factor via average-
current-mode control.
Non-Inverting Input for PFC Current Amplifier. The non-inverting input of the PFC current
amplifier and also the output of multiplier. Proper external compensation circuits result in
excellent input power factor via average-current-mode control.
Peak Current Limit Setting for PFC.
PWM Feedback Input. The control input for voltage-loop feedback of PWM stage. It is
internally pulled high through a 6.5kΩ resistance. Usually an external opto-coupler from
secondary feedback circuit is connected to this pin.
PWM Current Sense. The current-sense input for the flyback PWM. Via a current-sense
resistor, this pin provides the control input for peak-current-mode control and cycle-by-cycle
current limiting.
Ground. Signal ground.
PWM Soft-Start. During startup, the SS pin charges an external capacitor with a 50µA
(RI=24kΩ) constant current source. The voltage on FBPWM is clamped by SS during startup.
In the event of a protection condition occurring and/or PWM being disabled, the SS pin is
quickly discharged.
PWM Gate Drive. The totem-pole output drive for the flyback PWM MOSFET. This pin is
internally clamped under 17V to protect the MOSFET.
Ground. Power ground.
PFC Gate Drive. The totem-pole output drive for the PFC MOSFET. This pin is internally
clamped under 17V to protect the MOSFET.
Supply. The power-supply pin.
Ready-Signal Output. This pin outputs a ready signal to control the power-on sequence. Once
the SG6905 is turned on and the FBPFC (PFC feedback input) voltage is higher than 2.7V, the
pin locks to HIGH impedance. Disabling the SG6905 resets this pin to LOW.
Remote On/Off. The PFC stage disables whenever the voltage at this pin exceeds 2.45V.
Voltage Feedback Input for PFC. The feedback input for PFC voltage loop. The inverting
input of PFC error-amp. This pin is connected to the PFC output through a divider network.
Error-Amp Output for PFC Voltage Feedback Loop. The error-amp output for PFC voltage
feedback loop. A compensation network (usually a capacitor) is connected between this pin
and ground. A large capacitor value results in a narrow bandwidth and hence improves the
power factor.
Input AC Current. Before startup, this input is used to provide startup current for VDD. For
normal operation, this input is used to provide current reference for the multiplier.
© 2007 Fairchild Semiconductor Corporation
SG6905 • Rev. 1.1.2
5
www.fairchildsemi.com
5 Page 
Electrical Characteristics
VDD=15V, TA=25°C, unless otherwise noted.
Symbol
Parameter
RDY Section
VFB-RDY- RDY is a High Impedance at the Voltage of
HIGH FBPFC>VFB-RDY-HIGH and PFC_ON Low
IFB-RDY- The Leakage Current of RDY is a High
HIGH Impedance at the Voltage of FBPFC
VOL Output-Voltage Low for RDY is Failed
OTP Section
IOTP OTP Pin Output Current
VOTP-ON
VOTP-OFF
totp
Recovery Level on OTP
OTP Threshold Voltage
OTP Debounce Time
Soft-Start Section
ISS Constant Current Output for Soft-Start
RD Discharge RDSon
Conditions
Min. Typ. Max. Units
FBPFC=2V
ISINK=1mA
2.6 2.7 2.8
V
10 μA
0.5 V
RI=24kΩ
RI=24kΩ
90 100 110
1.35 1.40 1.45
1.15 1.20 1.25
8 25
μA
V
V
μs
RT=24kΩ
44 50 56
FBPWM=FBOPEN-LOOP
470
µA
Ω
Figure 5. PWM Frequency
© 2007 Fairchild Semiconductor Corporation
SG6905 • Rev. 1.1.2
11
www.fairchildsemi.com
11 Page | ||
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| PDF Descargar | [ Datasheet SG6905SY.PDF ] | |
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