OB2538 Datasheet PDF - On-Bright Electronics

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OB2538
On-Bright Electronics

Part Number OB2538
Description High Precision CC/CV Primary-Side PWM Controller
Page 10 Pages


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OB2538
High Precision CC/CV Primary-Side PWM Controller
Product Specification
GENERAL DESCRIPTION
OB2538 is a high performance offline PWM Power
switch for low power AC/DC charger and adaptor
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.
OB2538 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 OB2538.
.
FEATURES
„ 5% Constant Voltage Regulation, 5%
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
APPLICATIONS
Low Power AC/DC offline SMPS for
„ Cell Phone Charger
„ Digital Cameras Charger
„ Small Power Adaptor
„ Auxiliary Power for PC, TV etc.
„ Linear Regulator/RCC Replacement
OB2538 is offered in DIP8 package.
Fig.1. Typical CC/CV Curve
TYPICAL APPLICATION
©On-Bright Electronics
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_253800



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OB2538
High Precision CC/CV Primary-Side PWM Controller
GENERAL INFORMATION
Pin Configuration
The pin map is shown as below for DIP8.
VDD 1
8 GND
COMP
2
7 GND
INV 3
6 DRAIN
CS 4
5 DRAIN
Ordering Information
Part Number
Description
OB2538AP
DIP8, Pb-free, Tube
Package Dissipation Rating
Package
RθJA (/W)
DIP8
75
Note: Drain Pin Connected 100mm2 PCB copper clad.
.
Absolute Maximum Ratings
Parameter
Value
Drain Voltage (off state)
-0.3V to Bvdss
VDD Voltage
VDD Zener Clamp
Continuous Current
-0.3 to VDD_clamp
10 mA
COMP Voltage
-0.3 to 7V
CS Input Voltage
-0.3 to 7V
INV Input Voltage
-0.3 to 7V
Max Operating Junction
Temperature TJ
Min/Max Storage
Temperature Tstg
150 oC
-55 to 150 oC
Lead Temperature
(Soldering, 10secs)
260 oC
Note: Stresses beyond those listed under “absolute maximum
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
©On-Bright Electronics
Confidential
-2-
Preliminary Datasheet
OB_DOC_DS_253800



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Marking Information
OB2538
High Precision CC/CV Primary-Side PWM Controller
TERMINAL ASSIGNMENTS
Pin Num Pin Name
1 VDD
2 COMP
3 INV
4 CS
5/6 DRAIN
7/8 GND
I/O Description
P Power Supply
I Loop Compensation for CV Stability
The voltage feedback from auxiliary winding. Connected to resistor
I divider from auxiliary winding reflecting output voltage. PWM duty
cycle is determined by EA output and current sense signal at pin 4.
I Current sense input
O
HV MOSFET Drain Pin. The Drain pin is connected to the primary
lead of the transformer
P Ground
OUTPUT POWER TABLE
Product
OB2538
230VAC±15%
Adapter1
20W
85-264VAC
Adapter1
15W
Notes:
1. Maximum practical continuous power in an Adapter design with sufficient drain pattern as a heat sink, at 50ambient.
©On-Bright Electronics
Confidential
-3-
Preliminary Datasheet
OB_DOC_DS_253800



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OB2538
High Precision CC/CV Primary-Side PWM Controller
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_253800



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