OB2532
High Precision CC/CV Primary-Side PWM Controller
Product Specification
FEATURES
OB2532 is a high performance offline PWM
controller for low power AC/DC charger and
adapter applications. It operates in primary-side
sensing
and
regulation.
Consequently,
opto-coupler and TL431 could be eliminated.
Proprietary Constant Voltage (CV) and Constant
Current (CC) control is integrated as shown in the
figure below.
In CC control, the current and output power setting
can be adjusted externally by the sense resistor
Rs at CS pin. In CV control, multi-mode operations
are utilized to achieve high performance and high
efficiency. In addition, good load regulation is
achieved by the built-in cable drop compensation.
Device operates in PFM in CC mode as well at
large load condition and it operates in PWM with
frequency reduction at light/medium load.
OB2532 offers power on soft start control and
protection coverage with auto-recovery features
including Cycle-by-Cycle current limiting, VDD
OVP, VDD clamp and UVLO. Excellent EMI
performance is achieved with On-Bright
proprietary frequency shuffling technique.
High precision constant voltage (CV) and constant
current (CC) can be achieved by OB2532.
.
±5% Constant Voltage Regulation at
Universal AC input
High Precision Constant Current Regulation at
Universal AC input
Primary-side Sensing and Regulation Without
TL431 and Opto-coupler
Programmable CV and CC Regulation
Adjustable Constant Current and Output
Power Setting
Built-in Secondary Constant Current Control
with Primary Side Feedback
Built-in Adaptive Current Peak Regulation
Built-in Primary winding inductance
compensation
Programmable Cable drop Compensation
Power on Soft-start
Built-in Leading Edge Blanking (LEB)
Cycle-by-Cycle Current Limiting
VDD Under Voltage Lockout with Hysteresis
(UVLO)
VDD OVP
VDD Clamp
en
t
ia
lt
o
Ly
co
n
GENERAL DESCRIPTION
C
on
f
id
APPLICATIONS
Low Power AC/DC offline SMPS for
Cell Phone Charger
Digital Cameras Charger
Small Power Adapter
Auxiliary Power for PC, TV etc.
Linear Regulator/RCC Replacement
ht
OB2532 is offered in SOT23-6 package.
rig
Fig.1. Typical CC/CV Curve
O
nB
TYPICAL APPLICATION
©On-Bright Electronics
Confidential
-1-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
Package Dissipation Rating
Package
RθJA (℃/W)
SOT23-6
200
GENERAL INFORMATION
Pin Configuration
The pin map is shown as below for SOT23-6.
Value
-0.3 to VDD_clamp
Ly
co
Absolute Maximum Ratings
Parameter
VDD Voltage
VDD Zener Clamp
Continuous Current
COMP Voltage
CS Input Voltage
INV Input Voltage
Max Operating Junction
Temperature TJ
Min/Max Storage
Temperature Tstg
Lead Temperature
(Soldering, 10secs)
n
.
10 mA
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
260 oC
Note: Stresses beyond those listed under “absolute maximum
en
t
ratings” may cause permanent damage to the device. These
are stress ratings only, functional operation of the device at
these or any other conditions beyond those indicated under
“recommended operating conditions” is not implied. Exposure
to absolute maximum-rated conditions for extended periods
may affect device reliability.
O
nB
rig
ht
C
on
f
id
Ordering Information
Part Number
Description
OB2532MP
SOT23-6, Pb-free, T&R
-55 to 150 oC
ia
lt
o
150 oC
©On-Bright Electronics
Confidential
-2-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
lt
o
Ly
co
n
Marking Information
3
CS
I
4
INV
I
5
6
COMP
VDD
I
P
Description
Ground
Totem-pole gate drive output for power MOSFET.
Current sense input. Connected to MOSFET current sensing resistor
node.
The voltage feedback from auxiliary winding. Connected to resistor
divider from auxiliary winding reflecting output voltage. PWM duty cycle
is determined by EA output and current sense signal at pin 3.
Loop Compensation for CV Stability
Power Supply
en
t
I/O
P
O
id
Pin Name
GND
GATE
O
nB
rig
ht
C
on
f
Pin Num
1
2
ia
TERMINAL ASSIGNMENTS
©On-Bright Electronics
Confidential
-3-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
O
nB
rig
ht
C
on
f
id
en
t
ia
lt
o
Ly
co
n
BLOCK DIAGRAM
©On-Bright Electronics
Confidential
-4-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
ELECTRICAL CHARACTERISTICS
(TA = 25℃, VDD=16V, if not otherwise noted)
Symbol
Parameter
Test Conditions
Min Typ
Max Unit
Supply Voltage (VDD) Section
Standby Current
VDD=13V
I DD op
Operation Current
Operation supply current
INV=2V, CS=0V,
VDD=18V
2
3
UVLO(ON)
VDD Under Voltage Lockout
Enter
VDD falling
9.0
10.5 V
UVLO(OFF)
VDD Under Voltage Lockout Exit
VDD rising
VDD_clamp
Maximum VDD operation voltage IDD=10mA
OVP
Over voltage protection
Threshold
Td_oc
OCP Propagation delay
ZSENSE_IN
Input Impedance
T_ss
Soft start time
Frequency Section
IC Maximum frequency
Freq_Nom
System Nominal switch
frequency
uA
Ly
co
mA
27
28.5
30
V
26
27.5
29
V
o
16.0 V
lt
C
△f/Freq
on
f
Freq_MaxNote 1
Freq_startup
ia
Over current threshold
en
t
Vth_oc
20
13.5 14.8
625
880 910
ns
940
110
Kohm
17
55
INV=0V, Comp=5V
Frequency shuffling range
mV
ns
50
id
LEB time
8.2
Ramp VDD until gate
shut down
Current Sense Input Section
TLEB
5
n
I DD ST
60
ms
65
KHz
50
KHz
14
KHz
+/-6
%
Vref_EA
Reference voltage for EA
1.97 2
DC gain of EA
rig
Gain
ht
Error Amplifier section
nB
I_COMP_MAX
Max. Cable compensation
current
INV=2V, Comp=0V
2.03 V
60
dB
37.5
uA
O
Gate Drive Output Section
VOL
Output Low Level
Io=20mA
VOH
Output High Level
Io=20mA
V_clamp
Output Clamp Voltage Level
T_r
Output Rising Time
T_f
Output Falling Time
1
8
V
V
16
V
CL=0.5nF
650
nS
CL=0.5nF
40
nS
Note:
1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of 60Khz
nominal occurs at maximum output power or the transition point from CV to CC.
©On-Bright Electronics
Confidential
-5-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
CHARACTERIZATION PLOTS
110
Istartup(uA)
65.0
60.0
50.0
20
50
80
Temperature(℃)
110
110
2.5
2.0
1.5
1.0
-40
-10
20
50
80
Temperature(℃)
110
O
nB
rig
ht
C
on
f
id
20
50
80
Temperature(℃)
3.0
ia
55.0
-10
-10
Istartup(uA) vs Temperature(℃)
Freq_Max(KHz) vs Temperature(℃)
70.0
-40
n
-40
o
20
50
80
Temperature(℃)
lt
-10
16.00
15.50
15.00
14.50
14.00
13.50
13.00
Ly
co
UVLO(OFF)(V)
-40
Freq_Max(KHz)
UVLO(OFF)(V) vs Temperature(℃)
en
t
UVLO(ON)(V)
UVLO(ON)(V) vs Temperature( ℃)
10.5
10.0
9.5
9.0
8.5
8.0
7.5
©On-Bright Electronics
Confidential
-6-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
OPERATION DESCRIPTION
OB2532 is a cost effective PWM controller
optimized for off-line low power AC/DC
applications including battery chargers and
adapters. It operates in primary side sensing
and regulation, thus opto-coupler and TL431
are not required. Proprietary built-in CV and CC
control can achieve high precision CC/CV
control meeting most adapter and charger
application requirements.
NP
⋅ IP
NS
(1)
Ly
co
IS =
n
During MOSFET turn-on time, the load current is
supplied from the output filter capacitor Co. The
current in the primary winding ramps up. When
MOSFET turns off, the primary current transfers to
the secondary at the amplitude of
The auxiliary voltage reflects the output voltage as
shown in fig.2 and it is given by
z Startup Current and Start up Control
Startup current of OB2532 is designed to be
very low so that VDD could be charged up
above UVLO threshold and starts up quickly. A
large value startup resistor can therefore be
used to minimize the power loss in application.
V AUX =
N AUX
⋅ (VO + ΔV )
NS
(2)
lt
o
Where ΔV indicates the drop voltage of the
output Diode.
en
t
ia
z Operating Current
The Operating current of OB2532 is as low as
2.5mA. Good efficiency is achieved with the
low operating current together with ‘Muti-mode’
control features.
on
f
id
z Soft Start
OB2532 features an internal soft start to
minimize the component electrical over-stress
during power on startup. As soon as VDD
reaches UVLO (OFF), the control algorithm will
ramp peak current voltage threshold gradually
from nearly zero to normal setting of 0.90V.
Every restart is a soft start.
O
nB
rig
ht
C
z CC/CV Operation
OB2532 is designed to produce good CC/CV
control characteristic as shown in the Fig. 1.
In charger applications, a discharged battery
charging starts in the CC portion of the curve
until it is nearly full charged and smoothly
switches to operate in CV portion of the curve.
In an AC/DC adapter, the normal operation
occurs only on the CV portion of the curve.
The CC portion provides output current limiting.
In CV operation, the output voltage is regulated
through the primary side control. In CC
operation mode, OB2532 will regulate the
output current constant regardless of the output
voltage drop.
z Principle of Operation
To support OB2532 proprietary CC/CV control,
system needs to be designed in DCM mode for
flyback system (Refer to Typical Application
Diagram on page1).
In the DCM flyback converter, the output
voltage can be sensed via the auxiliary winding.
©On-Bright Electronics
Fig.2. Auxiliary voltage waveform
Via a resistor divider connected between the
auxiliary winding and INV (pin 3), the auxiliary
voltage is sampled at the end of the
de-magnetization and it is hold until the next
sampling. The sampled voltage is compared with
Vref (2.0V) and the error is amplified. The error
amplifier output COMP reflects the load condition
and controls the PWM switching frequency to
regulate the output voltage, thus constant output
voltage can be achieved.
When sampled voltage is below Vref and the error
amplifier output COMP reaches its maximum, the
switching frequency is controlled by the sampled
voltage thus the output voltage to regulate the
output current, thus the constant output current
can be achieved.
z Adjustable CC point and Output Power
In OB2532, the CC point and maximum output
power can be externally adjusted by external
current sense resistor Rs at CS pin as illustrated in
Typical Application Diagram. The output power is
adjusted through CC point change. The larger
Confidential
-7-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
Rs, the smaller CC point is, and the smaller
output power becomes, and vice versa as
shown in Fig.3.
spectrum minimizes the conduction band EMI and
therefore eases the system design.
Current Sensing and Leading Edge
Blanking
Cycle-by-Cycle current limiting is offered in
OB2532. The switch current is detected by a
sense resistor into the CS pin. An internal leading
edge blanking circuit chops off the sensed voltage
spike at initial power MOSFET on state so that the
external RC filtering on sense input is no longer
needed. The PWM duty cycle is determined by the
current sense input voltage and the EA output
voltage.
z
Vo
n
Large Rs
Ly
co
Small Rs
Io
z Gate Drive
The external power MOSFET is driven by a
dedicated gate driver of OB2532. Too weak the
gate drive strength results in higher conduction
and switch loss of MOSFET while too strong gate
drive compromises EMI.
A good tradeoff is achieved through the built-in
totem pole gate design with right output strength
control.
o
Fig.3 Adjustable output power by changing Rs
ia
en
t
1
LP FSW I p2
2
(3)
rig
ht
C
on
f
Where Lp indicate the inductance of primary
winding and Ip is the peak current of primary
winding.
Refer to the equation 3, the change of the
primary winding inductance results in the
change of the maximum output power and the
constant output current in CC mode. To
compensate the change from variations of
primary winding inductance, the switching
frequency is locked by an internal loop such
that the switching frequency is
FSW =
1
2TDemag
z Protection Control
Good power supply system reliability is achieved
with its rich protection features including
Cycle-by-Cycle current limiting (OCP), VDD clamp,
Power on Soft Start, and Under Voltage Lockout
on VDD (UVLO).
VDD is supplied by transformer auxiliary winding
output. The output of OB2532 is shut down when
VDD drops below UVLO (ON) limit and the power
converter enters power on start-up sequence
thereafter.
(4)
Since TDemag is inversely proportional to the
inductance, as a result, the product Lp and fsw
is constant, thus the maximum output power
and constant current in CC mode will not
change as primary winding inductance
changes. Up to ±10% variation of the primary
winding inductance can be compensated.
nB
O
z Programmable Cable drop Compensation
In OB2532, cable drop compensation is
implemented to achieve good load regulation. An
offset voltage is generated at INV by an internal
current flowing into the resister divider. The current
is inversely proportional to the voltage across pin
COMP, as a result, it is inversely proportional to
the output load current, thus the drop due to the
cable loss can be compensated. As the load
current decreases from full-load to no-load, the
offset voltage at INV will increase. It can also be
programmed by adjusting the resistance of the
divider to compensate the drop for various cable
lines used.
id
Po MAX =
lt
z Operation switching frequency
The switching frequency of OB2532 is
adaptively controlled according to the load
conditions and the operation modes. No
external frequency setting components are
required. The operation switching frequency at
maximum output power is set to 60K Hz
internally.
For flyback operating in DCM, The maximum
output power is given by
Frequency
shuffling
for
EMI
improvement
The frequency shuffling (switching frequency
modulation) is implemented in OB2532. The
oscillation frequency is modulated so that the
tone energy is spread out. The spread
z
©On-Bright Electronics
Confidential
-8-
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
Symbol
O
nB
rig
A
A1
A2
b
c
D
E
E1
e
e1
L
θ
ht
C
on
f
id
en
t
ia
lt
o
Ly
co
n
PACKAGE MECHANICAL DATA
©On-Bright Electronics
Dimensions In Millimeters
Min
Max
1.000
1.300
0.000
0.150
1.000
1.200
0.300
0.500
0.100
0.200
2.800
3.020
1.500
1.700
2.600
3.000
0.950 (BSC)
1.800
2.000
0.300
0.600
0º
8º
Confidential
-9-
Dimensions In Inches
Min
Max
0.039
0.051
0.000
0.006
0.039
0.047
0.012
0.020
0.004
0.008
0.110
0.119
0.059
0.067
0.102
0.118
0.037 (BSC)
0.071
0.079
0.012
0.024
0º
8º
Datasheet
OB_DOC_DS_2532A0
OB2532
High Precision CC/CV Primary-Side PWM Controller
IMPORTANT NOTICE
n
RIGHT TO MAKE CHANGES
On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements,
improvements and other changes to its products and services at any time and to discontinue any product
or service without notice. Customers should obtain the latest relevant information before placing orders
and should verify that such information is current and complete.
o
Ly
co
WARRANTY INFORMATION
On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable
at the time of sale in accordance with its standard warranty. Testing and other quality control techniques
are used to the extent it deems necessary to support this warranty. Except where mandated by
government requirements, testing of all parameters of each product is not necessarily performed.
On-Bright Electronics Corp. assumes no liability for application assistance or customer product design.
Customers are responsible for their products and applications using On-Bright’s components, data sheet
and application notes. To minimize the risks associated with customer products and applications,
customers should provide adequate design and operating safeguards.
ia
lt
LIFE SUPPORT
On-Bright Electronics Corp.’s products are not designed to be used as components in devices intended to
support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims
resulting from the use of its products in medical applications.
O
nB
rig
ht
C
on
f
id
en
t
MILITARY
On-Bright Electronics Corp.’s products are not designed for use in military applications. On-Bright
Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in
military applications.
©On-Bright Electronics
Confidential
- 10 -
Datasheet
OB_DOC_DS_2532A0
