PT2602A
Secondary-Side SR Switch
GENERAL DESCRIPTION
PT2602A is a high performance secondary
side switch for synchronous rectification (SR) in
DCM operation flyback.
Using SR to replace diode can effectively
reduce the secondary side rectifier power
dissipation and increase efficiency for system.
PT2602A is offered in SOP-8 package.
FEATURES
Match DCM and Quasi-Resonant flyback
converter
Supports
High-side
and
Low-side
rectification
No need external power supply
Adapters/Chargers
Flyback converters
APPLICATIONS
ORDERING INFORMATION
PACKAGE
SOP-8
TEMPERATURE
RANGE
-40℃ to 85℃
ORDERING PART
NUMBER
PT2602AESOH
TRANSPORT
MEDIA
Tape and Reel
4000 units
MARKING
PT2602A
xxxxxX
TYPICAL APPLICATION CIRCUIT
C7
GND
VCC
C3
DB1
C1
R0
D1
C4
R6
R2
C6
U2
R7
SW
5V+
AC In
R1
VCC
FR1
D3
C2
FB
R5
CRC
U1
T1
DRAIN
5V-
CS
GND
R3
R4
C5
5V+
C3
DB1
C1
R0
R2
C4
U2
T1
SW
VCC
GND
C6
5V-
D1
R6
AC In
R1
VCC
FR1
D3
C2
FB
R5
CRC
U1
DRAIN
CS
GND
R3
C7
R7
R4
C5
Figure1. Typical Application of PT2602A(U2)
CR POWTECH (SHANGHAI) CO., LTD.
PT2602A_DS_Rev EN1.0
WWW.CRPOWTECH.COM
Page 1
PT2602A
Secondary-Side SR Switch
ABSOLUTE MAXIMUM RATINGS
SYM
VCC
SW
T
J
T
STG
T
LEAD
JA
(Note1)
PARAMETER
Voltage at VCC to GND
Voltage at SW to GND
Operating Junction Temperature
Storage Temperature
Lead Temperature (Soldering, 10 sec)
Thermal Resistance (Junction to Ambient)
ESD (Human Body Model)
VALUE
-0.3 to 8
-0.3 to 45
-40 to 150
-55 to 150
300
184
2000
UNIT
V
V
℃
℃
℃
℃/W
V
Note 1:
Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent
damages to the device. Functional operation of the device at these or any other conditions beyond those
indicated under “Recommended Operating Conditions” is not implied. For maximum safe operating
conditions, refer to Electrical Characteristics.
SIMPLIFIED BLOCK DIAGRAM
SW
VCC
LDO
Control
Logic
Driver
GND
Figure 3. Simplified Block Diagram of PT2602A
CR POWTECH (SHANGHAI) CO., LTD.
PT2602A_DS_Rev EN1.0
WWW.CRPOWTECH.COM
Page 3
PT2602A
Secondary-Side SR Switch
OPERATION DESCRIPTION
The synchronous rectification can replace
Schottky diode to improve the efficiency in DCM
flyback converters. A power supply capacitor is
connected between VCC and GND. An internal
LDO circuit is adopted for its power supply
during the primary switch on time.
V
MOS_OFF
V
MOS_ON
T
ON_D
T
OFF_D
t
V
SR
I
SR
V
DET
Ipk
Startup Current and Start up Control
GATE
According to the figure 1, when the the primary
switch turns on, the power start from SW pin
through LDO to VCC pin. When VCC voltage
achieve VCC
ON
, the SR circuit start to work. And
when the VCC voltage drop below VCC
OFF
, the
SR circuit enter into restart mode. As shown in
figure 4.
SW
VCC
LDO
V
LDO
t
Figure 5. SR turn on and off waveform
Leading Edge Blanking
In order to avoid turning off by mistake, the
leading edge blanking circuit is adopted. When
the SR MOSFET is turned on, it will not be
turned off within the leading edge blanking time.
VCC
VCC
ON
VCC
OFF
GND
t
RC Snubber Circuit
In some applications such as startup, output short
protection, the system may go into slight CCM
condition. To suppress the reverse spike voltage
across the SR MOSFET, a RC snubber circuit is
suggested to be place between SW and GND. As
shown in figure 6.
Figure 4. VCC supply circuit and waveform
Operating Mode
When the secondary current first flows through
the body diode of SR MOSFET, the voltage of
SW pin will be lower than V
MOS_ON
, the SR
MOSFET turns on and the conduction loss
reduce, until the current through SR MOSFET
decrease near to 0, which means the voltage of
SW recovers to internal MOSFET turn off
threshold, the SR MOSFET turns off. As shown
in figure 5.
C6
C7
GND
VCC
U2
C7
R7
R7
SW
U2
VCC
GND
SW
C6
Figure 6. RC snubber for SR
CR POWTECH (SHANGHAI) CO., LTD.
PT2602A_DS_Rev EN1.0
WWW.CRPOWTECH.COM
Page 5
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