Richtek R7731AGE Schematic [ru]
Burst Triple Mode PWM Flyback Controller
R7731A
General Description
The R7731A is a high-perf ormance, 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
da maged by supply over voltage, the R7731A output 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 a nd 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 require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
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 Limit
zz
zz
z Feedback Open Protection
zz
zz
z Over Voltage Protection
zz
zz
z Over Temperature Protection
zz
zz
z Over Load Protection
zz
zz
z Soft Driving for Reducing EMI
zz
zz
z Driver Capability
zz
zz
z High Noise Immunity
zz
zz
z Opto-Coupler Short Protection
zz
zz
z RoHS Compliant and Halogen Free
zz
±±
±200mA
±±
μμ
μA)
μμ
Applications
z Ada ptor and Battery Charger
z A TX Standby Power
z Set-T op Box (STB)
z D VD and CD(R)
z TV/Monitor Standby Power
z PC Peripherals
Marking Information
R7731AGE
IDP=W
R7731AGE
RichTek
R7731A
GNYMDNN
R7731A-10 August 2011
IDP= : Product Code
W : Date Code
R7731AGN : Product Number
YMDNN : Date Code
www.richtek.com
1
R7731A
Pin Configurations
GATE
VDD CS
(TOP VIEW)
RTNCCOMPGND
678
5
4
56
23
GND
SOT-23-6 DIP-8
COMP
RT
Typical Application Circuit
AC Mains
(90V to 265V)
RT
R7731A
COMP
GND
VDD
GATE
CS
23
GATE VDD NC CS
4
*
VO+
VO-
* : See Application Information
Functional Pin Description
Pi n No.
SOT-23-6 DIP8
1 8 GND Ground.
2 7 COMP
3 5 RT Set the switching frequency by connect ing a resistor to GND.
4 4 CS Pr i mary Cu rrent Sense.
5 2 VDD IC Power Supply.
6 1 GA TE Gate Driver Output to drive t he exte rn al M OSFET.
-- 3, 6 NC
2
Pin N a m e Pin Function
Comparator Input. By connecting an opto-coupler to this pin, the peak
current set poi nt is adjust ed acc or di ngly t o the output power re qui re ment.
No Internal Connection.
R7731A-10 August 2011www.richtek.com
Function Block Diagram
R7731A
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
R7731A-10 August 2011
www.richtek.com
3
R7731A
Absolute Maximum Ratings (Note 1)
z Supply Input V oltage, V
z GATE Pin---------------------------------------------------------------------------------------------------------------------- −0.3V to 20V
z RT, COMP, CS Pin ---------------------------------------------------------------------------------------------------------- −0.3V to 6.5V
z I
------------------------------------------------------------------------------------------------------------------------------- 10mA
DD
z Power Dissipation, P
------------------------------------------------------------------------------------------------- −0.3V to 30V
DD
@ TA = 25°C
D
SOT-23-6 ---------------------------------------------------------------------------------------------------------------------- 0.4W
DIP-8 --------------------------------------------------------------------------------------------------------------------------- 0.714W
z Package Thermal Re sistance (Note 2)
SOT-23-6, θJA----------------------------------------------------------------------------------------------------------------- 250°C/W
DIP-8, θJA---------------------------------------------------------------------------------------------------------------------- 140°C/W
z Junction T emperature------------------------------------------------------------------------------------------------------- 150°C
z Lead T e mperature (Soldering, 10 sec.)--------------------------------------------------------------------------------- 260 °C
z Storage T emperature Range ---------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------------ 4kV
MM (Ma chine Mode)-------------------------------------------------------------------------------------------------------- 250V
Recommended Operating Conditions (Note 4)
z Supply Input V oltage, V
z Operating Frequency ------------------------------------------------------------------------------------------------------- 50k to 130kHz
z Junction T emperature Range---------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient T emperature Range---------------------------------------------------------------------------------------------- −40°C to 85°C
------------------------------------------------------------------------------------------------- 12V to 25V
DD
Electrical Characteristics
(V
= 15V, VDD bypass capacitor=0.1μF, RT = 100kΩ, T
DD
Parameter Symbol Test Conditions Min Typ Max Unit
VD D Se ction
VDD Over V olt age P rotection Level V
On Threshold Voltage V
VDD On/Off Hysteresis V
Start-up Current I
Op eratin g C urrent I
VDD Holdup M ode Hyst er esis
Endi ng Lev el
VDD Holdup M ode Ent ry Level V
VDD Clamp Volt age V
Osci llator Section (RT pi n)
Nor mal P WM Frequency f
OVP
TH_ON
DD_HYS
DD_ST
DD_OP
V
DD_HYS
DD_LOW
DD_CLAMP
OSC
= 25°C, unless otherwise specified)
A
25.5 27 28.5 V
13 14 15 V
3 4 5 V
V
V
V
= V
DD
= 15V , RT = 100kΩ,
V
DD
– 0.1V -- 20 30 μA
TH_ON
GATE = Open, V
< 1.6 V -- 11. 5 -- V
COMP
< 1.6 V -- 11 -- V
COMP
COMP
= 2.5V
-- 1.1 2.2 mA
-- 29 -- V
R
= 100kΩ 60 65 70 kHz
T
To be continued
R7731A-10 August 2011www.richtek.com
4
R7731A
Parameter Symbol Test Conditions Min Typ Max Unit
Frequency Jittering Range -- ±6 -- %
PWM Frequency Jitter Period T
Maximum Duty Cycle D
Frequency Variation Versus VDD
Deviation
Frequency Variation Versus
Te mpe ra ture D ev ia ti on
For 65 kHz -- 4 -- ms
JIT
70 75 80 %
MAX
f
V
DV
T
f
DT
= 12V to 25V -- -- 2 %
DD
= −30°C to 10 5°C (Not e 5) -- -- 5 %
A
CO MP Input Section
Open Loop Voltage V
CO MP Open-loop Pr ote cti on Del ay
Cycles
Short Circuit Current I
COMP_OP
T
OLP
ZERO
COMP pin open 5.2 5.6 6 V
R
V
= 100kΩ -- 60 -- ms
T
= 0V -- 1.2 2.2 mA
COMP
Current-Se nse Section
Init ia l Peak Curre n t Li mit Offse t V
Leading Edg e Blan king Time T
0.8 0.85 0.9 V
CSTH
-- 420 520 ns
LEB
Pr opagation Delay Ti me TPD -- 100 -- ns
GATE Section
Risi ng T ime TR V
F a lling Time TF V
= 15V, CL = 1nF -- 250 350 ns
DD
= 15V, CL = 1nF -- 150 25 0 ns
DD
Gat e Ou tpu t Clam pin g Voltage V
Over Temperat ur e Protection T
OTP Hysteresis T
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. θ
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.
is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of
JA
JEDEC 51-3 thermal measurement standard.
VDD = 22V -- 12 -- V
CLAMP
140 -- -- °C
OTP
OTP_HYS
-- 30 -- °C
R7731A-10 August 2011
www.richtek.com
5
Loading...