Richtek R7731GE Schematic [ru]
Burst Triple Mode PWM Flyback Controller
R7731
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
Features
zz
Very Low Start-Up Current (<30
z
zz
zz
z 10/14V UVLO
zz
zz
z Soft-Start Function
zz
zz
z Current Mode Control
zz
zz
z Jittering Switching Frequency
zz
zz
z Internal Leading Edge Blanking
zz
zz
z Built-in Slope Compensation
zz
zz
z Burst Triple Mode PWM for Green-Mode
zz
zz
z Cycle-by-Cycle Current Limiting
zz
zz
z Feedback Open Protection
zz
zz
z Output Over Voltage Protection
zz
zz
z Over Temperature Protection
zz
zz
z Over Load Protection
zz
zz
z Soft Driving for Reducing EMI
zz
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z High Noise Immunity
zz
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z Opto Coupler Short Protection
zz
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z RoHS Compliant and Halogen Free
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μμ
μA)
μμ
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
AC Mains
(90V to 265V)
RT
COMP
GND
VDD
R7731
GATE
CS
VO+
VO-
DS7731-03 March 2011 www.richtek.com
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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)
CSVDDGATE
4
56
23
GND COMP RT
SOT-23-6
RTNCCOMPGND
678
5
23
GATE VDD NC CS
DIP-8
4
DS7731-03 March 2011www.richtek.com
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Function Block Diagram
R7731
COMP
CS
Brown out
sensing
COMP open
sensing
OLP
Constant
Power
LEB
X3
SS
Slope
Ramp
Shutdown
Logic
Counter
-
+
PWM
comparator
OTP
Jittering Oscillator
Dmax
POR
Triple Mode
Burst
OVP
UVLO
S
R
+
-
+
-
Bias &
Bandgap
Q
COMP
V
V
V
VDD
27V
14V/10V
RT
Soft
Driver
GATE
BURL
BURH
DD
GND
Functional Pin Description
Pin No.
SOT-23-6 DIP8
1 8 GND Ground.
2 7 COMP
3 5 RT Set the switching frequency by connecting a resistor to GND.
4 4 CS Primary Current Sense Pin.
5 2 VDD IC Power Supply Pin.
6 1 GATE Gate driver output to drive the external MOSFET.
-- 3, 6 NC
DS7731-03 March 2011 www.richtek.com
Pin Name Pin Function
Comparator Input Pin. By connecting a photo-coupler to this pin, the peak
current set point is adjusted accordingly to the output power requirement.
No Internal Connection.
3
R7731
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, V
z GATE Pin ---------------------------------------------------------------------------------------------------------------- 20V
z FB, RT, COMP, CS Pin ---------------------------------------------------------------------------------------------- 6.5V
z I
------------------------------------------------------------------------------------------------------------------------- 10mA
DD
z Power Dissipation, P
------------------------------------------------------------------------------------------- 30V
DD
@ TA = 25°C
D
SOT-23-6 ---------------------------------------------------------------------------------------------------------------- 0.4W
DIP-8 --------------------------------------------------------------------------------------------------------------------- 0.714W
z Package Thermal Resistance (Note 2)
z SOT-23-6, θ
z DIP-8, θ
z Junction Temperature ------------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------- 260°C
z Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
----------------------------------------------------------------------------------------------------------- 250°C/W
JA
---------------------------------------------------------------------------------------------------------------- 140°C/W
JA
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 4kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 250V
Recommended Operating Conditions (Note 4)
z Supply Input Voltage, V
z Operating Frequency ------------------------------------------------------------------------------------------------- 50k to 130kHz
z Junction Temperature Range ---------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range ---------------------------------------------------------------------------------------- −40°C to 85°C
------------------------------------------------------------------------------------------- 12V to 25V
DD
Electrical Characteristics
(V
= 15V, RT = 100kΩ, T
DD
Parameter Symbol Test Conditions Min Typ Max Unit
VDD Section
VDD Over Voltage Protection Level V
On Threshold Voltage V
VDD On/Off Hysteresis V
Start-Up Current I
Operating Current I
VDD Hold Up Mode Hysteresis
Ending Level
VDD Hold Up Mode Entry Level V
VDD Clamp Voltage V
Osci ll ator Sect ion (RT pin)
Normal PWM Frequency f
Frequency Jittering Range -- ± 4 -- %
Maximum Duty Cycle D
= 25°C, unless otherwise specified)
A
25.5 27 28.5 V
OVP
13 14 15 V
TH_ON
3 4 5 V
DD_hys
VDD = V
DD-ST
V
= 15V, RT = 100kΩ,
DD-OP
V
DD_hys
DD_Low
DD_Clamp
R
OS C
70 75 80 %
MAX
DD
GATE = Open, V
V
COMP
V
COMP
-- 29 -- V
= 100kΩ 60 65 70 kHz
T
– 0.1V -- 20 30 μA
TH_ON
COMP
= 2.5V
-- 1.1 2.2 mA
< 1.6V -- 11.5 -- V
< 1.6V -- 11 -- V
To be continued
DS7731-03 March 2011www.richtek.com
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