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Page No. : 1/10 DS‐RS2138‐03 September, 2009 www.Orister.com RS2138 High Precision CC/CV Primary‐Side PWM Power Switch General Description RS2138 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 431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the Fig.1. In CC control, the current and output power setting can be adju sted 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 wi th frequency reduction at light/medium load. RS2138 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 Frequ ency Jiggling. Features Applications

  • 5% Constant Voltage Regulation, 5% Constant Current Regulation at Universal AC input
  • Primary‐side Sensing and Regulation Without 431 and Opto‐ coupler
  • Power on Soft‐start
  • Built‐in Leading Edge Blanking (LEB)
  • Cycle‐by‐Cycle Current Limiting
  • VDD Under Voltage Lockout with Hysteresis (UVLO)
  • 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
  • Program cable drop compensation
  • VDD OVP and VDD Clamp
  • Available in an DIP‐8 Package
  • RoHS Compliant and 100% Lead (Pb)‐Free and Green (Halogen Free with Commercial Standard)
  • Cell Phone Charger
  • Digital Cameras Charger
  • Small Power Adaptor
  • Auxiliary Power for PC, TV etc.
  • Linear Regulator/RCC Replacement Fig.1. Typical CC/CV Curve

Page No. : 2/10 DS‐RS2138‐03 September, 2009 www.Orister.com This integrated circuit can be damaged by ESD. Orister Corporation recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. Application Circuits GND VOUT C1 C2 RS2138 COMP INV CS DRAIN DRAIN VCC GND GND C3 Naux R3 R4 R5 C5 C6 R6 Np Ns AC IN Pin Assignments DIP‐8 PACKAGE PIN SYMBOL DESCRIPTION

1 VDD Power Supply

2 COMP Loop Compensation for CV Stability

3 INV

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 4.

4 CS Current sense input

5,6 DRAIN HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer DIP‐8 7, 8 GND Ground

Ordering Information

Y is package & Pin Assignments designator : P: DIP‐8 Z is Lead Free designator : P: Commercial Standard, Lead (Pb) Free and Phosphorous (P) Free Package G: Green (Halogen Free with Commercial Standard)

Page No. : 3/10 DS‐RS2138‐03 September, 2009 www.Orister.com Block Diagram Absolute Maximum Ratings Symbol Parameter Range Units ‐ Drain Voltage (off state) ‐ 0.3V to Bvdss V ‐ VDD Voltage ‐ 0.3 to VDD_Clamp V ‐ VDD Zener Clamp Continuous Current 10 mA ‐ COMP Voltage ‐ 0.3 to 7 V ‐ CS Input Voltage ‐ 0.3 to 7 V ‐ INV Input Voltage ‐ 0.3 to 7 V TJ Junction Temperature ‐ 20 to 150 oC TOPR Operating Temperature Range ‐ 20 to +85 oC TSTG Storage Temperature Range ‐ 55 to 150 oC TLEAD Lead Temperature (Soldering, 10secs) 260 oC Note: Stress beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Exposure to absolute maximum‐rated conditions for extended periods may affect device reliability. Output Power Table Part No. Package 230VAC ±15% 85 to 265VAC RS2138P DIP‐8 20W 16W

Page No. : 4/10 DS‐RS2138‐03 September, 2009 www.Orister.com Electrical Characteristics (VDD=16V, TA=25°C, unless otherwise specified) Symbol Parameter Test Conditions Min. Typ. Max. Unit Supply Voltage (VDD) Section IDD_ST Standby current VDD=13V ‐ 5 20 uA IDD_OP Operation Current Operation supply current INV=2V,CS=0V, VDD=VDDG=20V ‐ 2.5 3.5 mA UVLO(ON) VDD Under Voltage Lockout Enter VDD falling 7.5 8.5 V UVLO(OFF) VDD Under Voltage Lockout Exit VDD rising 13.5 14.5 16.0 V OVP Over voltage protection voltage Ramp up VDD until gate clock is off 27.5 29.5 31.5 V VDD_Clamp Maximum VDD opertation voltage IDD=10mA 30.5 32.5 34.5 V Current Sense Input Section TLEB LEB time ‐ ‐ 540 ‐ ns Vth_oc Over current threshold ‐ 870 900 930 mV Td_oc OCP Propagation delay ‐ ‐ 150 ‐ ns ZSENSE_IN Input Impedance ‐ ‐ 50 ‐ KΩ Tss Soft start time ‐ ‐ 10 ‐ ms CV Section Freq_Nom System Nominal switch frequency ‐ ‐ 60 ‐ KHZ Freq_startup ‐ INV=0V, Comp=5V ‐ 14 ‐ KHZ Δf/Freq Frequency jitter range ‐ ‐ +/‐4 ‐ % Error Amplifier section VREF_EA Reference voltage for EA ‐ 1.97 2 2.03 V Gdc DC gain of the EA ‐ ‐ 60 ‐ dB I_COMP_MAX Max. Cable compensation current INV=2V, COMP=0V ‐ 42 ‐ uA Power MOSFET Section BVdss MOSFET Drain‐Source Breakdown Voltage ‐ ‐ 650 ‐ V RDS(on) Static Drain to Source On Resistance ‐ ‐ 3.0 3.6 Ω

Page No. : 5/10 DS‐RS2138‐03 September, 2009 www.Orister.com Detail Description RS2138 is a cost effective PWM power switch optimized for off‐line low power AC/DC applications including battery chargers and adaptors. It operates in primary side sensing and regulation, thus opto‐coupler and 431 are not required. Proprietary built‐in CV and CC control can achieve high precision CC/CV control meeting most adaptor an d charger application requirements. Startup Current and Start up Control Startup current of RS2138 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. Operating Curr ent The Operating current of RS2138 is as low as 2.5mA. Good efficiency is achieved with the low operating current together with Multi‐mode control features. Soft Start RS2138 features an internal soft start to minimize the component electrical over‐stress during power on startup. As soon as VDD reaches UVLO (O FF), 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. CC/CV Operation RS2138 is designed to produce good CC/CV control characteristic as shown in the Fig. 1. In charger applications, a discharged ba ttery 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 ope ration, the output voltage is regulated through the primary side control. In CC operation mode, RS2138 will regulate the output current constant regardless of the output voltage drop. Principle of Operation To support RS2138 proprietary CC/CV control, system needs to be designed in DCM mode for flyback system (Refer to Typical Application Di agram). In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding. During MOSFET turn‐on time, the load current is supplied from the output filter capacitor C O. The current in the primary winding ramps up. When MOSFET turns off, the primary current transfers to the secondary at the amplitude of P S P S IN NI × = The auxiliary voltage reflects the output voltage as shown in fig.2 and it is given by ) V V (N NV O S AUX AUX Δ + × = Where ΔV indicates the drop voltage of the output Diode.

Page No. : 6/10 DS‐RS2138‐03 September, 2009 www.Orister.com 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 demagnetization 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 V REF 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. Adjustable CC point and Output Power In RS2138, the CC point and maximum output power can be externally ad justed 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 RS, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Fig.3. Fig.3. Adjustable output power by changing RS Operation switching frequency The switching frequency of RS2138 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 60KHz internally. For flyback operating in DCM, The maximum output power is given by MAX P SW PO I F L2 1P × × × = Where LP indicate the inductance of primary winding and IP is the peak current of primary winding.

Page No. : 7/10 DS‐RS2138‐03 September, 2009 www.Orister.com 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 frequenc y is DEMAG SW T 2 1F = 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. Frequency Jiggling for EMI improvement The Frequency Jiggling (switching frequency modulation) is implemented in RS2138. The oscillation fre quency is modulated so that the tone energy is spread out. The spread 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 RS2138 current mode PWM control. The switch current is detected by a sense resistor into the CS pin. An inte rnal leading edge blanking circuit chops off the sensed voltage spike at initial internal 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. Gate Drive The internal power MOSFET in RS2138 is driven by a dedicated gate driver for power switch control. 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 th e built‐in totem pole gate design with right output strength control. Programmable Cable drop Compensation In RS2138, 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 prog rammed by adjusting the resistance of the divider to compensate the drop for various cable lines used. 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 Lockou t on VDD(UVLO). VDD is supplied by transformer auxiliary winding output. The output of RS2138 is shut down when VDD drops below UVLO (ON) limit and Switcher enters power on start‐up sequence thereafter.

Page No. : 8/10 DS‐RS2138‐03 September, 2009 www.Orister.com DIP‐8 Dimension NOTES: A. All linear dimensions are in inches (millimeters). B. This drawing is subject to change without notice. C. Falls within JEDEC MS‐001.

Page No. : 9/10 DS‐RS2138‐03 September, 2009 www.Orister.com Soldering Methods for Orister’s Products 1. Storage environment: Temperature=10oC~35oC Humidity=65%±15% 2. Reflow soldering of surface‐mount devices Profile Feature Sn‐Pb Eutectic Assembly Pb‐Free Assembly Average ramp‐up rate (TL to TP) <3oC/sec <3oC/sec Preheat ‐ Temperature Min (Tsmin) ‐ Temperature Max (Tsmax) ‐ Time (min to max) (ts) 100oC 150oC 60~120 sec 150oC 200oC 60~180 sec Tsmax to TL ‐ Ramp‐up Rate <3oC/sec <3oC/sec Time maintained above: ‐ Temperature (TL) ‐ Time (tL) 183oC 60~150 sec 217oC 60~150 sec Peak Temperature (TP) 240oC +0/‐5oC 260oC +0/‐5oC Time within 5oC of actual Peak Temperature (tP) 10~30 sec 20~40 sec Ramp‐down Rate <6oC/sec <6oC/sec Time 25oC to Peak Temperature <6 minutes <8 minutes 3. Flow (wave) soldering (solder dipping) Products Peak temperature Dipping time Pb devices. 245oC ±5oC 5sec ±1sec Pb‐Free devices. 260oC +0/‐5oC 5sec ±1sec Figure 1: Temperature profile tP tL Ramp-down Ramp-up Tsmax Tsmin Critical Zone TL to TP tS Preheat TL TP t 25oC to Peak Time Temperature

Page No. : 10/10 DS‐RS2138‐03 September, 2009 www.Orister.com Important Notice: © Orister Corporation Orister cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an Orister product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. Orister reserves the right to make changes to their products or specifications or to discontinue any prod uct or service without notice. Except as provided in Orister’s terms and conditions of sale, Orister assumes no liability whatsoever, and Orister disclaims any express or implied warranty relating to the sale and/or use of Orister products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any pate nt, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent Orister deems necessary to supp ort this warranty. Specific testing of all parameters of each device is not necessarily performed. Orister and the Orister logo are trademarks of Orister Corporation. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.