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Richtek Technology
Richtek Technology

R7731 Datasheet

Burst Triple-Mode PWM Flyback Controller


R7731 Datasheet Preview


R7731
Burst Triple Mode PWM Flyback Controller
General Description
The R7731 is a high performance, low cost, low start-up
current, current mode PWM controller with burst triple
mode to support green mode power saving operation. The
R7731 integrates functions of Soft-Start, Under Voltage
Lockout (UVLO), Leading Edge Blanking (LEB), Over
Temperature Protection (OTP), internal slope
compensation. It provides the users a superior AC/DC
power application of higher efficiency, low external
component counts and lower cost solution.
To protect the external power MOSFET from being
damaged by supply over voltage, the R7731 output driver
is clamped at 12V. Furthermore, R7731 features fruitful
protections like OLP (Over Load Protection) ,OVP (Over
Voltage Protection) to eliminate the external protection
circuits and provide reliable operation. R7731 is available
in SOT-23-6 and DIP-8 packages.
Applications
z Adaptor and Battery Charger
z ATX Standby Power
z Set Top Boxes (STB)
z DVD and CD(R)
z TV/Monitor Standby Power
z PC Peripherals
Typical Application Circuit
Features
z Very Low Start-Up Current (<30μA)
z 10/14V UVLO
z Soft-Start Function
z Current Mode Control
z Jittering Switching Frequency
z Internal Leading Edge Blanking
z Built-in Slope Compensation
z Burst Triple Mode PWM for Green-Mode
z Cycle-by-Cycle Current Limiting
z Feedback Open Protection
z Output Over Voltage Protection
z Over Temperature Protection
z Over Load Protection
z Soft Driving for Reducing EMI
z High Noise Immunity
z Opto Coupler Short Protection
z RoHS Compliant and Halogen Free
AC Mains
(90V to 265V)
VO+
VO-
RT VDD
R7731
COMP
GATE
GND
CS
DS7731-03 March 2011
www.richtek.com
1
Page 1

R7731
Ordering Information
R7731
Package Type
E : SOT-23-6
N : DIP-8
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area.
Pin Configurations
(TOP VIEW)
GATE VDD CS
65 4
23
GND COMP RT
SOT-23-6
GND COMP NC RT
8 7 65
2 34
GATE VDD NC CS
DIP-8
www.richtek.com
2
DS7731-03 March 2011
Page 2

Function Block Diagram
R7731
COMP
CS
Brown out
sensing
COMP open
sensing
OLP
Constant
Power
LEB X3
Shutdown
Logic
OTP
POR
OVP
+
-
27V
+
UVLO -
14V/10V
Counter
Bias &
Bandgap
SS
Slope
Ramp
Jittering Oscillator
Dmax
-
-
+
PWM
comparator
S
Q
R
Soft
Driver
Burst
Triple Mode
COMP
VBURL
VBURH
VDD
VDD
RT
GATE
GND
Functional Pin Description
Pin No.
SOT-23-6 DIP8
18
27
35
44
52
61
-- 3, 6
Pin Name
Pin Function
GND
COMP
RT
CS
VDD
GATE
NC
Ground.
Comparator Input Pin. By connecting a photo-coupler to this pin, the peak
current set point is adjusted accordingly to the output power requirement.
Set the switching frequency by connecting a resistor to GND.
Primary Current Sense Pin.
IC Power Supply Pin.
Gate driver output to drive the external MOSFET.
No Internal Connection.
DS7731-03 March 2011
www.richtek.com
3
Page 3
Part Number R7731
Manufactur Richtek Technology
Description Burst Triple-Mode PWM Flyback Controller
Total Page 11 Pages
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