Document
On-Bright Confidential to ACT
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
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Preliminary Datasheet
OB_DOC_DS_253800
On-Bright Confidential to ACT
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 T.