CS2842A, CS3842A, CS2843A, CS3843A. Off Line Current Mode PWM Control Circuit with Undervoltage Lockout

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CS242A, CS342A, CS243A, CS343A OffLine Current Mode PWM Control Circuit with Undervoltage Lockout The CS24XA, CS34XA provides all the necessary features to implement offline fixed frequency

1 CS242A, CS342A, CS243A, CS343A OffLine Current Mode PWM Control Circuit with Undervoltage Lockout The CS24XA, CS34XA provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components. The CS34XA family incorporates a new precision temperaturecontrolled oscillator with an internally trimmed discharge current to minimize variations in frequency. A precision dutycycle clamp eliminates the need for an external oscillator when a 50% dutycycle is used. Dutycycles greater than 50% are also possible. On board logic ensures that is stabilized before the output stage is enabled. Ion implant resistors provide tighter control of undervoltage lockout. Other features include low startup current, pulsebypulse current limiting, and a highcurrent totem pole output for driving capacitive loads, such as the gate of power MOSFET. The output is LOW in the off state, consistent with Nchannel devices. The CS34XA series of currentmode control ICs are available in and4 lead packages for surface mount (SO) applications as well as lead PDIP packages. Features Optimized for Offline Control Internally Trimmed Temperature Compensated Oscillator Maximum DutyCycle Clamp Stabilized Before Output Stage is Enabled Low Startup Current PulseByPulse Current Limiting Improved Undervoltage Lockout Double Pulse Suppression.0% Trimmed Bandgap Reference High Current Totem Pole Output 4 DIP N SUFFIX CASE 626 SO D SUFFIX CASE 75 SO4 D SUFFIX CASE 75A MARKING DIAGRAM 4 x = 2 or 3 y = 2 or 3 A = Assembly Location WL, L = Wafer Lot YY, Y = Year WW, W = Work Week x4ya AWL YYWW x4ya ALYWX CSx4yA AWLYWW ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page of this data sheet. Semiconductor Components Industries, LLC, 2006 July, 2006 Rev. 4 Publication Order Number: CS242A/D

2 CS242A, CS342A, CS243A, CS343A PIN CONNECTIONS DIP & SO COMP V FB Sense V OUT SO4 4 COMP NC NC V FB NC Pwr Sense V OUT NC Pwr 34 V Undervoltage Lockout Circuit Pwr 6 V/0 V (.4 V/7.6 V) Set/ Reset 5.0 V Reference Internal Bias 2.50 V Output Enable Oscillator NOR V OUT + 2R S V FB COMP Error Amplifier V C R.0 V R Current Sensing Comparator PWM Latch Pwr Sense ( ) Indicates CS243A/343A Figure. Block Diagram 2

3 CS242A, CS342A, CS243A, CS343A MAXIMUM RATINGS* Rating Value Unit Supply Voltage (I CC < 30 ma) Self Limiting Supply Voltage (Low Impedance Source) 30 V Output Current ±.0 A Output Energy (Capacitive Load) 5.0 μj Analog Inputs (V FB, Sense) 0.3 to V Error Amp Output Sink Current 0 ma Package Thermal Resistance, PDIP JunctiontoCase, R θjc JunctiontoAmbient, R θja Package Thermal Resistance, SO JunctiontoCase, R θjc JunctiontoAmbient, R θja Package Thermal Resistance, SO4 JunctiontoCase, R θjc JunctiontoAmbient, R θja Lead Temperature Soldering: Wave Solder (through hole styles only) (Note ) Reflow (SMD styles only) (Note 2). 0 second maximum second maximum above 3 C. *The maximum package power dissipation must be observed. 260 peak 230 peak C C ELECTRICAL CHARACTERISTICS (25 T A 5 for CS242A/CS243A, 0 T A 70 for CS342A/CS343A. = 5 V*; R T = 60 Ω, C T = μf for triangular mode, R T = 0 kω, C T = 3.3 nf for sawtooth mode (see Figure 7); unless otherwise stated.) CS242A/CS243A CS342A/CS343A Characteristic Test Conditions Min Typ Max Min Typ Max Unit Reference Section Output Voltage T J = 25 C, I OUT =.0 ma V Line Regulation 2 V IN 25 V mv Load Regulation.0 I OUT 20 ma mv Temperature Stability Note mv/ C Total Output Variation Line, Load, Temperature (Note 3.) V Output Noise Voltage 0 Hz f 0 khz, T J = 25 C (Note 3.) μv Long Term Stability T A = 25 C,.0 khrs. (Note 3.) mv Output Short Circuit T A = 25 C ma Oscillator Section Initial Accuracy Sawtooth Mode (see Figure 7), T J = 25 C Triangular Mode (see Figure 7), T J = 25 C khz khz Voltage Stability 2 25 V % Temperature Stability Sawtooth Mode T MIN T A T MAX (Note 3.) Triangular Mode T MIN T A T MAX (Note 3.) % % Amplitude peak to peak.7.7 V Discharge Current T J = 25 C 7.5 T MIN T A T MAX ma ma 3. These parameters, although guaranteed, are not 00% tested in production. *Adjust above the start threshold before setting at 5 V. 3

4 CS242A, CS342A, CS243A, CS343A ELECTRICAL CHARACTERISTICS (continued) (25 T A 5 for CS242A/CS243A, 0 T A 70 for CS342A/CS343A. = 5 V*; R T = 60 Ω, C T = μf for triangular mode, R T = 0 kω, C T = 3.3 nf for sawtooth mode (see Figure 7); unless otherwise stated.) CS242A/CS243A CS342A/CS343A Characteristic Test Conditions Min Typ Max Min Typ Max Unit Error Amp Section Input Voltage V COMP = 2.5 V V Input Bias Current V FB = μa A VOL 2.0 V OUT 4.0 V db Unity Gain Bandwidth Note MHz PSRR 2 25 V db Output Sink Current V FB = 2.7 V, V COMP =. V ma Output Source Current V FB = 2.3 V, V COMP = 5.0 V ma V OUT High V FB = 2.3 V, 5 kω to ground V V OUT Low V FB = 2.7 V, 5 kω to V Current Sense Section Gain Notes 5 & V/V Maximum Input Signal V COMP = 5.0 V (Note 5.) V PSRR 2 25 V (Note 5.) db Input Bias Current V SENSE = μa Delay to Output T J = 25 C (Note 4.) ns Output Section Output Low Level I SINK = 20 ma I SINK = 200 ma V V Output High Level I SOURCE = 20 ma I SOURCE = 200 ma V V Rise Time T J = 25 C, C L =.0 nf (Note 4.) ns Fall Time T J = 25 C, C L =.0 nf (Note 4.) ns Output Leakage UVLO Active, V OUT = μa Total Standby Current Startup Current ma Operating Supply Current V FB = V SENSE = 0 V, R T = 0 kω, C T = 3.3 nf 7 7 ma Zener Voltage I CC = 25 ma V 4. These parameters, although guaranteed, are not 00% tested in production. 5. Parameters measured at trip point of latch with V FB = Gain defined as: A = ΔV COMP /ΔV SENSE ; 0 V SENSE 0. V. *Adjust above the start threshold before setting at 5 V. 4

5 CS242A, CS342A, CS243A, CS343A ELECTRICAL CHARACTERISTICS (continued) (25 T A 5 for CS242A/CS243A, 0 T A 70 for CS342A/CS343A. = 5 V*; R T = 60 Ω, C T = μf for triangular mode, R T = 0 kω, C T = 3.3 nf for sawtooth mode (see Figure 7); unless otherwise stated.) Characteristic Test Conditions CS242A CS342A CS243A/CS343A Min Typ Max Min Typ Max Min Typ Max Undervoltage Lockout Section Start Threshold V Min. Operating Voltage After Turn On V *Adjust above the start threshold before setting at 5 V. Unit PACKAGE PIN DESCRIPTION Package Pin Number DIP SO SO4 Symbol Description ÁÁÁÁ COMP Error amp output, used to compensate error amplifier V FB ÁÁÁÁ Error amp inverting input. ÁÁÁ Sense Noninverting input to Current Sense Comparator. ÁÁÁ Oscillator timing network with capacitor to ground, resistor to. ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ 5 5 Ground. ÁÁÁÁ 9 Pwr Output driver ground V OUT ÁÁÁÁ Output drive pin. ÁÁÁÁ Pwr Output driver positive supply ÁÁÁÁ Positive power supply. 4 ÁÁÁÁ Output of 5.0 V internal reference. ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ 2, 4, 6, 3 NC No connection. TYPICAL PERFORMANCE CHARACTERISTICS Frequency (khz) R T =.5 kω R T = 60 Ω R T = 0 kω Duty Cycle (%) C T (μf) k 2 k R T (Ω) 3 k 4 k 5 k 7 k 0 k Figure 2. Oscillator Frequency vs. C T Figure 3. Oscillator Duty Cycle vs. R T 5

6 CS242A, CS342A, CS243A, CS343A R T A 2N kω.0 kω ERROR AMP ADJUST 4.7 kω 00 kω 5.0 kω Sense ADJUST COMP V FB Sense V OUT 0. μf.0 kω.0 W 0. μf V OUT C T Figure 4. Test Circuit CIRCUIT DESCRIPTION ON/OFF Command to reset of IC RESET V ON V OFF CSX42A 6 V 0 V CSX43A.4 V 7.6 V EA Output Switch Current I CC I O < 5 ma <.0 ma V ON V OFF Figure 5. Typical Undervoltage Characteristics Undervoltage Lockout During Undervoltage Lockout (Figure 5), the output driver is biased to a high impedance state. The output should be shunted to ground with a resistor to prevent output leakage current from activating the power switch. PWM Waveform To generate the PWM waveform, the control voltage from the error amplifier is compared to a current sense signal which represents the peak output inductor current (Figure 6). An increase in causes the inductor current slope to increase, thus reducing the duty cycle. This is an inherent feedforward characteristic of current mode control, since the control voltage does not have to change during changes of input supply voltage. V O Figure 6. Timing Diagram for Key CS24B Parameters When the power supply sees a sudden large output current increase, the control voltage will increase allowing the duty cycle to momentarily increase. Since the duty cycle tends to exceed the maximum allowed to prevent transformer saturation in some power supplies, the internal oscillator waveform provides the maximum duty cycle clamp as programmed by the selection of oscillator components. Setting the Oscillator Oscillator timing capacitor, C T, is charged by through R T and discharged by an internal current source. During the discharge time, the internal clock signal blanks out the output to the Low state, thus providing a user selected maximum duty cycle clamp. Charge and discharge times are determined by the formula: 6

7 CS242A, CS342A, CS243A, CS343A tc RTCT ln Vlower VREF Vupper td RTCT ln IdRT Vlower VREF IdRT Vupper Substituting in typical values for the parameters in the above formulas: = 5.0 V V upper = 2.7 V V lower =.0 V I d =.3 ma t c R T C T td RTCT ln R T RT The frequency and maximum duty cycle can be determined using the Typical Performance Characteristic graphs. Grounding High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to pin in a single point ground. The transistor and 5.0 kω potentiometer, shown in the test circuit, are used to sample the oscillator waveform and apply and adjustable ramp to Sense. Timing Parameters V upper Sawtooth Mode Large R T ( 0 kω) Triangular Mode Small R T ( 700 kω) R T C T V lower t c t d V Internal Clock V Internal Clock Figure 7. Oscillator Timing Network and Parameters 7

8 CS242A, CS342A, CS243A, CS343A ORDERING INFORMATION Device Temperature Range Package Shipping CS242ALN DIP 50 Units/Rail CS243ALN DIP 50 Units/Rail 25 C to 5 C CS242ALD4 SO4 55 Units/Rail CS242ALDR4 SO Tape & Reel CS342AGN DIP 50 Units/Rail CS342AGD SO 9 Units/Rail CS342AGDR SO 2500 Tape & Reel CS342AGD4 SO4 55 Units/Rail CS342AGDR4 SO Tape & Reel 0 C to 70 C CS343AGN DIP 50 Units/Rail CS343AGD SO 9 Units/Rail CS343AGDR SO 2500 Tape & Reel CS343AGD4 SO4 55 Units/Rail CS343AGDR4 SO Tape & Reel

9 CS242A, CS342A, CS243A, CS343A PACKAGE DIMENSIONS DIP N SUFFIX CASE ISSUE L 5 B NOTES:. DIMENSION L TO CENTER OF LEAD WHEN FORMED PARALLEL. 2. PACKAGE CONTOUR OPTIONAL (ROUND OR SQUARE CORNERS). 3. DIMENSIONING AND TOLERANCING PER ANSI Y4.5M, 92. NOTE 2 T SEATING PLANE H 4 F A C N D K G 0.3 (0.005) M T A M B M L J M MILLIMETERS INCHES DIM MIN MAX MIN MAX A B C D F G 2.54 BSC 0.00 BSC H J K L 7.62 BSC BSC M 0 0 N SO D SUFFIX CASE 7507 ISSUE W X B Y Z H G A D 5 4 S C 0.25 (0.00) M Z Y S X S 0.25 (0.00) M SEATING PLANE Y 0.0 (0.004) M N X 45 M K J NOTES:. DIMENSIONING AND TOLERANCING PER ANSI Y4.5M, CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.5 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.27 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. MILLIMETERS INCHES DIM MIN MAX MIN MAX A B C D G.27 BSC BSC H J K M 0 0 N S

10 CS242A, CS342A, CS243A, CS343A PACKAGE DIMENSIONS T SEATING PLANE G A 4 D 4 PL 7 B K P 7 PL C 0.25 (0.00) M T B S A S SO4 D SUFFIX CASE 75A03 ISSUE F 0.25 (0.00) M B M NOTES:. DIMENSIONING AND TOLERANCING PER ANSI Y4.5M, CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.5 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.27 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. MILLIMETERS INCHES R X 45 F DIM MIN MAX MIN MAX A B C D M J F G.27 BSC BSC J K M P R ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. Typical parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including Typicals must be validated for each customer application by customer s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 563, Denver, Colorado 027 USA Phone: or Toll Free USA/Canada Fax: or Toll Free USA/Canada orderlit@onsemi.com N. American Technical Support: Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: Japan Customer Focus Center Phone: ON Semiconductor Website: Order Literature: For additional information, please contact your local Sales Representative CS242A/D

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