CS2841B. Automotive Current Mode PWM Control Circuit

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Automotive Current Mode PWM Control Circuit The CS2841B provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components.

1 Automotive Current Mode PWM Control Circuit The CS2841B provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components. The CS2841B (a variation of the CS2843A) is designed specifically for use in automotive operation. The low start threshold voltage of 8.0 V (typ), and the ability to survive 40 V automotive load dump transients are important for automotive subsystem designs. The CS2841 series has a history of quality and reliability in automotive applications. The CS2841B incorporates a precision temperaturecontrolled oscillator with an internally trimmed discharge current to minimize variations in frequency. 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. Features Optimized for OffLine Control Internally Trimmed Temperature Compensated Oscillator Maximum DutyCycle Clamp Stabilized Before Output Stage Enabled Low StartUp Current PulseByPulse Current Limiting Improved Undervoltage Lockout Double Pulse Suppression 1.0 % Trimmed Bandgap Reference High Current Totem Pole Output PbFree Packages are Available* PDIP8 N SUFFIX CASE 626 PIN CONNECTIONS AND MARKING DIAGRAM V FB Sense CS2841BEB AWL YYWWG PDIP8 SOIC14 D SUFFIX CASE 751A V OUT NC VFB NC Sense NC 1 CS2841BD14G AWLYWW SOIC14 14 NC PWR V OUT PWR CS2841B A WL YY, Y WW G = Device Code = Assembly Location = Wafer Lot = Year = Work Week = PbFree Package *For additional information on our PbFree strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 2 of this data sheet. Semiconductor Components Industries, LLC, 2008 March, 2008 Rev. 8 1 Publication Order Number: CS2841B/D

2 Undervoltage Lockout Circuit Pwr 8.0 V/7.4 V 2.5 V Set/ Reset Output Enable 5.0 V Reference Internal Bias Oscillator NOR V FB + Error Amplifier V C 2 R R 1.0 V S R Current Sensing Comparator PWM Latch V OUT Pwr Sense Figure 1. Block Diagram MAXIMUM RATINGS Rating Value Unit Supply Voltage (Low Impedance Source) 40 V Output Current ±1.0 A Output Energy (Capacitive Load) 5.0 J Analog Inputs (V FB, Sense) 0.3 to 5.5 V Error Amp Output Sink Current 10 ma Lead Temperature Soldering Wave Solder (through hole styles only) Note 1 Reflow (SMD styles only) Note peak 230 peak C C Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability seconds max seconds max above 183 C ORDERING INFORMATION Device Package Shipping CS2841BEBN8 PDIP8 50 Units / Rail CS2841BEBN8G PDIP8 (PbFree) 50 Units / Rail CS2841BED14 SOIC14 55 Units / Rail CS2841BED14G SOIC14 (PbFree) 55 Units / Rail CS2841BEDR14 SOIC / Tape & Reel CS2841BEDR14G SOIC14 (PbFree) 2500 / Tape & Reel For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. 2

3 ELECTRICAL CHARACTERISTICS (40 C T A 85 C, R T = 680 k, C T = F for Triangular Mode, = 15 V (Note 3), R T = 10 k, C T = 3.3 nf for Sawtooth Mode (see Figure 7); unless otherwise specified.) Reference Section Characteristic Test Conditions Min Typ Max Unit Output Voltage T J = 25 C, I OUT = 1.0 ma V Line Regulation V mv Load Regulation 1.0 I OUT 20 ma mv Temperature Stability Note mv/ C Total Output Variation Line, Load, Temp. Note V Output Noise Voltage 10 Hz f 10 khz, T J = 25 C. Note 4 50 V Long Term Stability T A = 125 C, 1000 Hrs. Note mv Output Short Circuit T A = 25 C ma Oscillator Section Initial Accuracy Sawtooth Mode: T J = 25 C. See Figure 7. Sawtooth Mode: 40 C T A +85 C Triangular Mode: T J =25 C. See Figure khz khz khz Voltage Stability V % Temperature Stability Sawtooth Mode: T MIN T A T MAX. Note 4 Triangular Mode: T MIN T A T MAX. Note % % Amplitude V (Peak to Peak) 1.7 V Discharge Current T J = 25 C 7.4 T MIN T A T MAX ma ma Error Amp Section Input Voltage V = 2.5 V V Input Bias Current V FB = 0 V A A VOL 2.0 V OUT 4.0 V db Unity Gain Bandwidth Note MHz PSRR 8.4 V 16 V db Output Sink Current V FB = 2.7 V, V = 1.1 V ma Output Source Current V FB = 2.3 V, V = 5.0 V ma V OUT High V FB = 2.3 V, R L = 15 k to Ground V V OUT Low V FB = 2.7 V, R L = 15 k to V Current Sense Section Gain Notes 5 and V/V Maximum Input Signal V = 5.0 V. Note V PSRR 12 V 25 V. Note 5 70 db Input Bias Current V Sense = 0 V A Delay to Output T J = 25 C. Note ns 3. Adjust above the start threshold before setting at 15 V 4. These parameters, although guaranteed, are not 100% tested in production 5. Parameter measured at trip point of latch with V FB = 0 6. Gain defined as: A V VSense ; 0 V Sense 0.8 V. 3

4 ELECTRICAL CHARACTERISTICS (40 C T A 85 C, R T = 680 k, C T = F for Triangular Mode, = 15 V (Note 3), R T = 10 k, C T = 3.3 nf for Sawtooth Mode (see Figure 7); unless otherwise specified.) Characteristic Test Conditions Min Typ Max Unit 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 = 1.0 nf. Note ns Fall Time T J = 25 C, C L = 1.0 nf. Note ns Output Leakage Undervoltage Active, V OUT = A Total Standby Current Startup Current ma Operating Supply Current I CC V FB = V Sense = 0 V, R T = 10 k, C T = 3.3 nf ma Undervoltage Lockout Section Start Threshold V Min. Operating Voltage After Turn On V 7. These parameters, although guaranteed, are not 100% tested in production. PACKAGE PIN DESCRIPTION PACKAGE PIN # PDIP8 SOIC14 PIN SYMBOL FUNCTION 1 1 Error Amp Output, Used to Compensate Error Amplifier 2 3 V FB Error Amp Inverting Input 3 5 Sense Noninverting Input to Current Sense Comparator 4 7 Oscillator Timing Network with Capacitor to Ground, Resistor to 5 8 Ground 9 Pwr Output Driver Ground 6 10 V OUT Output Drive Pin 11 Pwr Output Driver Positive Supply 7 12 Positive Power Supply 8 14 Output of 5.0 V Internal Reference 2, 4, 6, 13 NC No Connection 4

5 TYPICAL PERFORMANCE CHARACTERISTICS Frequency (khz) R T = 1.5 k R T = 680 Duty Cycle (%) R T = 10 k C T ( F) k 2 k R T ( ) 3 k 4 k 5 k 7 k 10 k Figure 2. Oscillator Frequency vs. C T Figure 3. Oscillator Duty Cycle vs. R T R T 4.7 k 2N k A 1.0 k Error Amp Adjust 4.7 k 5.0 k Sense Adjust V FB CS2841B Sense V OUT 1.0 k 1.0 W V OUT C T Figure 4. Test Circuit 5

6 CIRCUIT DESCRIPTION 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. 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 components. ON/OFF Command to Reset of IC V ON = 8.0 V V OFF = 7.4 V R T C T I CC < 15 ma < 1.0 ma 7.4 V 8.0 V Timing Parameters V upper V lower t c t d Figure 5. Typical Undervoltage Characteristics PWM Waveform To generate the PWM waveform, the control voltage from the error amplifier is compared to a current sense signal representing 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. Sawtooth Mode Large R T ( 10 k ) Triangular Mode Small R T ( 700 k ) V Internal Clock V RESET EA Output Switch Current Internal Clock Figure 7. Oscillator Timing Network and Parameters I O V O Figure 6. Timing Diagram for Key CS2841B Parameters 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 general formulas: 6

7 tc RTCT ln Vlower VREF Vupper td RTCT ln IdRT Vupper VREF IdRT Vlower Substituting in typical values for the parameters in the above formulas: VREF 5.0 V Vupper 2.7 V Vlower 1.0 V Id 8.3 ma tc RTCT The frequency and maximum duty cycle can be determined from 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 k potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to Sense. td RTCT ln R T RT VPR Q1 2n4401 C1 C2 68 F 68 F C3 4.7 pf 100 V R1 4.7 k DZ1 13 V 1N5243B MURS120T3 D1 R T D2 MBR360 9T C4 L1 2.2 H C F C F C7 = ma C8 C9 10 F C10 R5 2.0 k C nf VC PV OUT CS2841B SENSE P V FB R k 1.0 % R k 1.0 % R4 C nf R k C F C14 47 pf R6 Q2 1.0 k MTDISN06VTL4 R % Figure 8. Flyback Application 7

8 VPR R2 10 C1 100 F 100 V L1 100 H D1 1N5818 C2 330 F C3 R1 12 k 17 V C4 C5 10 F C6 R4 3.0 k V OUT CS2841B SENSE FB C F R3 10 R5 100 Q1 MTP12N10 C9 470 pf R8 2.0 k C8 1.0 nf D2 1N5818 R6 10 k R7 1.0 Input Voltage Range: 8.0 V to 16 V Output Voltage: ma > 300 ma Figure 9. Boost Application PACKAGE THERMAL DATA Parameter PDIP8 SOIC14 Unit R JC Typical C/W R JA Typical C/W 8

9 PACKAGE DIMENSIONS PDIP8 CASE ISSUE L NOTE B 1 4 F A C N D K G 0.13 (0.005) M T A M B M T SEATING PLANE H L J M NOTES: 1. DIMENSION L TO CENTER OF LEAD WHEN FORMED PARALLEL. 2. PACKAGE CONTOUR OPTIONAL (ROUND OR SQUARE CORNERS). 3. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, MILLIMETERS INCHES DIM MIN MAX MIN MAX A B C D F G 2.54 BSC BSC H J K L 7.62 BSC BSC M N

10 PACKAGE DIMENSIONS B T SEATING PLANE G D 14 PL 7 A K P 7 PL C 0.25 (0.010) M T B S A S SOIC14 CASE 751A03 ISSUE J 0.25 (0.010) M B M NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE (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 1.27 BSC BSC J K M P R SOLDERING FOOTPRINT 14X X X PITCH DIMENSIONS: MILLIMETERS 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 5163, Denver, Colorado 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 CS2841B/D

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

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