Richtek R7731AGE Schematic [ru]
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R7731A
Burst Triple Mode PWM Flyback Controller
General Description
The R7731A is a high-performance, low cost, low start-up current and current mode PWM controller with burst triple mode to support green mode power saving operation. The R7731A integrates functions of soft start, Under Voltage LockOut (UVLO), Leading Edge Blanking (LEB), Over Temperature Protection (OTP) and 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 R7731Aoutput driver is clamped at 12V. Furthermore, R7731A features fruitful protections like Over Load Protection (OLP) and Over Voltage Protection (OVP) to eliminate the external protection circuits and provide reliable operation. R7731A is available in SOT-23-6 and DIP-8 packages.
Ordering Information
R7731A 
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.
Features
zVery Low Start-up Current (<30μA)
z10/14V UVLO
zSoft Start Function
zCurrent Mode Control
zJittering Switching Frequency
zInternal Leading Edge Blanking
zBuilt-in Slope Compensation
zBurst Triple Mode PWM for Green-Mode
zCycle-by-Cycle Current Limit
zFeedback Open Protection
zOver Voltage Protection
zOver Temperature Protection
zOver Load Protection
zSoft Driving for Reducing EMI
zDriver Capability ±200mA
zHigh Noise Immunity
zOpto-Coupler Short Protection
zRoHS Compliant and Halogen Free
Applications
zAdaptor and Battery Charger
zATX Standby Power
zSet-Top Box (STB)
zDVDand CD(R)
zTV/Monitor Standby Power
zPC Peripherals
Marking Information
R7731AGE
IDP=W
IDP= : Product Code
W : Date Code
R7731AGE
RichTek |
R7731AGN : Product Number |
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YMDNN : Date Code |
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R7731A |
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GNYMDNN |
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R7731A-10 August 2011 |
www.richtek.com |
1
R7731A
Pin Configurations
(TOP VIEW)
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GND COMP NC |
RT |
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GATE VDD CS |
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8 |
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7 |
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6 |
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5 |
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GND COMP |
RT |
GATE |
VDD |
NC |
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CS |
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SOT-23-6 |
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DIP-8 |
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Typical Application Circuit
VO+ AC Mains 
(90V to 265V)
VO-
RT |
VDD |
* |
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R7731A |
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COMP |
GATE |
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GND |
CS |
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* : See Application Information |
Functional Pin Description |
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Pin No. |
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Pin Name |
Pin Function |
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SOT-23-6 |
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DIP8 |
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1 |
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8 |
GND |
Ground. |
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2 |
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7 |
COMP |
Comparator Input. By connecting an opto-coupler to this pin, the peak |
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current set point is adjusted accordingly to the output power requirement. |
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3 |
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5 |
RT |
Set the switching frequency by connecting a resistor to GND. |
4 |
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4 |
CS |
Primary Current Sense. |
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5 |
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2 |
VDD |
IC Power Supply. |
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6 |
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1 |
GATE |
Gate Driver Output to drive the external MOSFET. |
-- |
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3, 6 |
NC |
No Internal Connection. |
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www.richtek.com |
R7731A-10 August 2011 |
2
R7731A
Function Block Diagram
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OVP + |
VDD |
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POR |
- |
27V |
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Shutdown |
OTP |
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Logic |
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+ |
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Brown out |
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UVLO |
- |
14V/10V |
sensing |
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COMP open |
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Counter |
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Bias & |
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sensing |
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Bandgap |
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OLP |
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Jittering Oscillator |
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Constant |
SS |
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RT |
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Dmax |
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Power |
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Soft |
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S |
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Driver |
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- |
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Q |
GATE |
COMP |
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R |
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- |
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+ |
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PWM |
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CS |
Slope |
comparator |
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Ramp |
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COMP |
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Burst |
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VBURL |
LEB |
X3 |
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Triple Mode |
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VBURH |
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VDD |
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GND |
R7731A-10 August 2011 |
www.richtek.com |
3
R7731A
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VDD ------------------------------------------------------------------------------------------------- |
−0.3V to 30V |
z GATE Pin ---------------------------------------------------------------------------------------------------------------------- |
−0.3V to 20V |
z RT, COMP, CS Pin ---------------------------------------------------------------------------------------------------------- |
−0.3V to 6.5V |
z IDD ------------------------------------------------------------------------------------------------------------------------------- |
10mA |
z Power Dissipation, PD @ TA = 25°C |
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SOT-23-6 ---------------------------------------------------------------------------------------------------------------------- |
0.4W |
DIP-8 --------------------------------------------------------------------------------------------------------------------------- |
0.714W |
z Package Thermal Resistance (Note 2) |
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SOT-23-6, θJA ----------------------------------------------------------------------------------------------------------------- |
250°C/W |
DIP-8, θJA ---------------------------------------------------------------------------------------------------------------------- |
140°C/W |
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) |
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HBM (Human Body Mode) ------------------------------------------------------------------------------------------------ |
4kV |
MM (Machine Mode) -------------------------------------------------------------------------------------------------------- |
250V |
Recommended Operating Conditions |
(Note 4) |
z Supply Input Voltage, VDD ------------------------------------------------------------------------------------------------- |
12V to 25V |
z Operating Frequency ------------------------------------------------------------------------------------------------------- |
50k to 130kHz |
z Junction Temperature Range ---------------------------------------------------------------------------------------------- |
−40°C to 125°C |
z Ambient Temperature Range ---------------------------------------------------------------------------------------------- |
−40°C to 85°C |
Electrical Characteristics
(VDD = 15V, VDD bypass capacitor=0.1μF, RT = 100kΩ, TA = 25°C, unless otherwise specified)
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Parameter |
Symbol |
Test Conditions |
Min |
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Typ |
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Max |
Unit |
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VDD Section |
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VDD Over Voltage Protection Level |
VOVP |
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25.5 |
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27 |
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28.5 |
V |
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On Threshold Voltage |
VTH_ON |
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13 |
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14 |
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15 |
V |
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VDD On/Off Hysteresis |
VDD_HYS |
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3 |
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4 |
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5 |
V |
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Start-up Current |
IDD_ST |
VDD = VTH_ON – 0.1V |
-- |
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20 |
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30 |
μA |
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Operating Current |
IDD_OP |
VDD = 15V, RT = 100kΩ, |
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1.1 |
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2.2 |
mA |
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GATE = Open, VCOMP = 2.5V |
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VDD Holdup Mode Hysteresis |
VDD_HYS |
VCOMP < 1.6V |
-- |
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11.5 |
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-- |
V |
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Ending Level |
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VDD Holdup Mode Entry Level |
VDD_LOW |
VCOMP < 1.6V |
-- |
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11 |
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-- |
V |
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VDD Clamp Voltage |
VDD_CLAMP |
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-- |
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29 |
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-- |
V |
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Oscillator Section (RT pin) |
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Normal PWM Frequency |
fOSC |
RT = 100kΩ |
60 |
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65 |
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70 |
kHz |
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To be continued |
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www.richtek.com |
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R7731A-10 |
August 2011 |
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4
R7731A
Parameter |
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Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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Frequency Jittering Range |
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-- |
±6 |
-- |
% |
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PWM Frequency Jitter Period |
TJIT |
For 65 kHz |
-- |
4 |
-- |
ms |
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Maximum Duty Cycle |
DMAX |
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70 |
75 |
80 |
% |
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Frequency Variation Versus VDD |
fDV |
VDD = 12V to 25V |
-- |
-- |
2 |
% |
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Deviation |
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Frequency Variation Versus |
fDT |
TA = −30°C to 105°C (Note 5) |
-- |
-- |
5 |
% |
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Temperature Deviation |
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COMP Input Section |
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Open Loop Voltage |
VCOMP_OP |
COMP pin open |
5.2 |
5.6 |
6 |
V |
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COMP Open-loop Protection Delay |
T |
OLP |
R = 100kΩ |
-- |
60 |
-- |
ms |
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Cycles |
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T |
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Short Circuit Current |
IZERO |
VCOMP = 0V |
-- |
1.2 |
2.2 |
mA |
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Current-Sense Section |
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Initial Peak Current Limit Offset |
VCSTH |
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0.8 |
0.85 |
0.9 |
V |
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Leading Edge Blanking Time |
TLEB |
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-- |
420 |
520 |
ns |
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Propagation Delay Time |
TPD |
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-- |
100 |
-- |
ns |
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GATE Section |
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Rising Time |
TR |
VDD = 15V, CL = 1nF |
-- |
250 |
350 |
ns |
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Falling Time |
TF |
VDD = 15V, CL = 1nF |
-- |
150 |
250 |
ns |
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Gate Output Clamping Voltage |
VCLAMP |
VDD = 22V |
-- |
12 |
-- |
V |
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Over Temperature Protection |
TOTP |
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140 |
-- |
-- |
°C |
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OTP Hysteresis |
TOTP_HYS |
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-- |
30 |
-- |
°C |
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Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design.
R7731A-10 August 2011 |
www.richtek.com |
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