CS2842A, CS3842A, CS2843A, CS3843A Off-Line Current Mode PWM Control Circuit with Undervoltage Lockout The CS284XA, CS384XA provides all the necessary features to implement off-line fixed frequency current-mode control with a minimum number of external components. The CS384XA family incorporates a new precision temperature-controlled oscillator with an internally trimmed discharge current to minimize variations in frequency. A precision duty-cycle clamp eliminates the need for an external oscillator when a 50% duty-cycle is used. Duty-cycles greater than 50% are also possible. On board logic ensures that VREF is stabilized before the output stage is enabled. Ion implant resistors provide tighter control of undervoltage lockout. Other features include low startup current, pulse-by-pulse current limiting, and a high-current totem pole output for driving capacitive loads, such as the gate of power MOSFET. The output is LOW in the off state, consistent with N-channel devices. The CS384XA series of current-mode control ICs are available in 8 and14 lead packages for surface mount (SO) applications as well as 8 lead PDIP packages. http://onsemi.com MARKING DIAGRAM 8 x84yA AWL YYWW DIP-8 N SUFFIX CASE 626 8 1 8 1 8 1 SO-8 D SUFFIX CASE 751 x84yA ALYWX 1 14 14 1 SO-14 D SUFFIX CASE 751A CSx84yA AWLYWW 1 Features * Optimized for Off-line Control * Internally Trimmed Temperature Compensated Oscillator * Maximum Duty-Cycle Clamp * VREF Stabilized Before Output Stage is Enabled * Low Startup Current * Pulse-By-Pulse Current Limiting * Improved Undervoltage Lockout * Double Pulse Suppression * 1.0% Trimmed Bandgap Reference * High Current Totem Pole Output Semiconductor Components Industries, LLC, 2001 June, 2001 - Rev. 3 x y A WL, L YY, Y WW, W = 2 or 3 = 2 or 3 = Assembly Location = Wafer Lot = Year = Work Week ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 8 of this data sheet. 1 Publication Order Number: CS2842A/D CS2842A, CS3842A, CS2843A, CS3843A PIN CONNECTIONS DIP-8 & SO-8 COMP 1 8 VFB SO-14 1 VCC Sense OSC VOUT GND VCC 14 VREF NC VCC VCC Pwr VOUT Pwr GND GND COMP NC VFB NC Sense NC OSC VREF VCC Pwr Undervoltage Lock-out Circuit 34 V Set/ Reset GND 5.0 V Reference VREF 16 V/10 V (8.4 V/7.6 V) Internal Bias 2.50 V Output Enable OSC NOR Oscillator VOUT + VFB COMP - Error Amplifier S 2R R VC R 1.0 V Current Sensing Comparator Sense ( ) Indicates CS2843A/3843A Figure 1. Block Diagram http://onsemi.com 2 PWM Latch Pwr GND CS2842A, CS3842A, CS2843A, CS3843A MAXIMUM RATINGS* Rating Value Unit Self Limiting - 30 V Output Current 1.0 A Output Energy (Capacitive Load) 5.0 J -0.3 to + 5.5 V Error Amp Output Sink Current 10 mA Package Thermal Resistance, PDIP-8 Junction-to-Case, RJC Junction-to-Ambient, RJA 52 100 CW CW Package Thermal Resistance, SO-8 Junction-to-Case, RJC Junction-to-Ambient, RJA 45 165 CW CW Package Thermal Resistance, SO-14 Junction-to-Case, RJC Junction-to-Ambient, RJA 30 125 CW CW 260 peak 230 peak C C Supply Voltage (ICC < 30 mA) Supply Voltage (Low Impedance Source) Analog Inputs (VFB, Sense) Lead Temperature Soldering: Wave Solder (through hole styles only) (Note 1) Reflow (SMD styles only) (Note 2) 1. 10 second maximum. 2. 60 second maximum above 183C. *The maximum package power dissipation must be observed. ELECTRICAL CHARACTERISTICS (-25 TA 85 for CS2842A/CS2843A, 0 TA 70 for CS3842A/CS3843A. VCC = 15 V*; RT = 680 , CT = 0.022 F for triangular mode, RT = 10 k, CT = 3.3 nF for sawtooth mode (see Figure 7); unless otherwise stated.) Characteristic Test Conditions CS2842A/CS2843A CS3842A/CS3843A Min Typ Max Min Typ Max Unit 4.95 5.00 5.05 4.90 5.00 5.10 V Reference Section Output Voltage TJ = 25C, IOUT = 1.0 mA Line Regulation 12 VIN 25 V - 6.0 20 - 6.0 20 mV Load Regulation 1.0 IOUT 20 mA - 6.0 25 - 6.0 25 mV Temperature Stability Note 3. - 0.2 0.4 - 0.2 0.4 mV/C Total Output Variation Line, Load, Temperature (Note 3.) 4.90 - 5.10 4.82 - 5.18 V Output Noise Voltage 10 Hz f 10 kHz, TJ = 25C (Note 3.) - 50 - - 50 - V Long Term Stability TA = 125C, 1.0 kHrs. (Note 3.) - 5.0 25 - 5.0 25 mV Output Short Circuit TA = 25C -30 -100 -180 -30 -100 -180 mA Initial Accuracy Sawtooth Mode (see Figure 7), TJ = 25C Triangular Mode (see Figure 7), TJ = 25C 47 47 52 52 57 57 47 44 52 52 57 60 kHz kHz Voltage Stability 12 VCC 25 V - 0.2 1.0 - 0.2 1.0 % Temperature Stability Sawtooth Mode TMIN TA TMAX (Note 3.) Triangular Mode TMIN TA TMAX (Note 3.) - - 5.0 8.0 - - - - 5.0 8.0 - - % % Amplitude OSC peak to peak - 1.7 - - 1.7 - V Discharge Current TJ = 25C TMIN TA TMAX 7.5 7.2 8.3 - 9.3 9.5 7.5 7.2 8.3 - 9.3 9.5 mA mA Oscillator Section 3. These parameters, although guaranteed, are not 100% tested in production. *Adjust VCC above the start threshold before setting at 15 V. http://onsemi.com 3 CS2842A, CS3842A, CS2843A, CS3843A ELECTRICAL CHARACTERISTICS (continued) (-25 TA 85 for CS2842A/CS2843A, 0 TA 70 for CS3842A/CS3843A. VCC = 15 V*; RT = 680 , CT = 0.022 F for triangular mode, RT = 10 k, CT = 3.3 nF for sawtooth mode (see Figure 7); unless otherwise stated.) Characteristic Test Conditions CS2842A/CS2843A CS3842A/CS3843A Min Typ Max Min Typ Max Unit 2.45 2.50 2.55 2.42 2.50 2.58 V Error Amp Section Input Voltage VCOMP = 2.5 V Input Bias Current VFB = 0 - -0.3 -1.0 - -0.3 -2.0 A AVOL 2.0 VOUT 4.0 V 65 90 - 65 90 - dB Unity Gain Bandwidth Note 4. 0.7 1.0 - 0.7 1.0 - MHz PSRR 12 VCC 25 V 60 70 - 60 70 - dB Output Sink Current VFB = 2.7 V, VCOMP = 1.1 V 2.0 6.0 - 2.0 6.0 - mA Output Source Current VFB = 2.3 V, VCOMP = 5.0 V -0.5 -0.8 - -0.5 -0.8 - mA VOUT High VFB = 2.3 V, 15 k to ground 5.0 6.0 - 5.0 6.0 - V VOUT Low VFB = 2.7 V, 15 k to VREF - 0.7 1.1 - 0.7 1.1 V Current Sense Section Gain Notes 5 & 6. 2.85 3.00 3.15 2.85 3.00 3.15 V/V Maximum Input Signal VCOMP = 5.0 V (Note 5.) 0.9 1.0 1.1 0.9 1.0 1.1 V PSRR 12 VCC 25 V (Note 5.) - 70 - - 70 - dB Input Bias Current VSENSE = 0 - -2.0 -10 - -2.0 -10 A Delay to Output TJ = 25C (Note 4.) - 150 300 - 150 300 ns Output Low Level ISINK = 20 mA ISINK = 200 mA - - 0.1 1.5 0.4 2.2 - - 0.1 1.5 0.4 2.2 V V Output High Level ISOURCE = 20 mA ISOURCE = 200 mA 13 12 13.5 13.5 - - 13 12 13.5 13.5 - - V V Rise Time TJ = 25C, CL = 1.0 nF (Note 4.) - 50 150 - 50 150 ns Fall Time TJ = 25C, CL = 1.0 nF (Note 4.) - 50 150 - 50 150 ns Output Leakage UVLO Active, VOUT = 0 - -0.01 -10.00 - -0.01 -10.00 A - 0.5 1.0 - 0.5 1.0 mA Output Section Total Standby Current Startup Current - Operating Supply Current VFB = VSENSE = 0 V, RT = 10 k, CT = 3.3 nF 11 17 - 11 17 - mA VCC Zener Voltage ICC = 25 mA - 34 - - 34 - V 4. These parameters, although guaranteed, are not 100% tested in production. 5. Parameters measured at trip point of latch with VFB = 0. 6. Gain defined as: A = VCOMP/VSENSE; 0 VSENSE 0.8 V. *Adjust VCC above the start threshold before setting at 15 V. http://onsemi.com 4 CS2842A, CS3842A, CS2843A, CS3843A ELECTRICAL CHARACTERISTICS (continued) (-25 TA 85 for CS2842A/CS2843A, 0 TA 70 for CS3842A/CS3843A. VCC = 15 V*; RT = 680 , CT = 0.022 F for triangular mode, RT = 10 k, CT = 3.3 nF for sawtooth mode (see Figure 7); unless otherwise stated.) CS2842A Characteristic Test Conditions CS3842A CS2843A/CS3843A Min Typ Max Min Typ Max Min Typ Max Unit 15 16 17 14.5 16 17.5 7.8 8.4 9.0 V 9.0 10 11 8.5 10 11.5 7.0 7.6 8.2 V Undervoltage Lockout Section Start Threshold - Min. Operating Voltage After Turn On *Adjust VCC above the start threshold before setting at 15 V. PACKAGE PIN DESCRIPTION Package Pin Number AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA AAAAA AAAA AAAA AAAAA AAAAAAAAAAAAAAAAAAA DIP-8 SO-8 SO-14 Symbol 1 1 1 COMP 2 2 3 VFB 3 3 5 Sense 4 4 7 OSC Oscillator timing network with capacitor to ground, resistor to VREF. 5 5 8 GND Ground. - - 9 Pwr GND 6 6 10 VOUT - - 11 VCC Pwr 7 7 12 VCC Positive power supply. 8 8 14 VREF Output of 5.0 V internal reference. - - 2, 4, 6, 13 NC Description Error amp output, used to compensate error amplifier. Error amp inverting input. Noninverting input to Current Sense Comparator. Output driver ground. Output drive pin. Output driver positive supply. No connection. TYPICAL PERFORMANCE CHARACTERISTICS 100 900 90 RT = 680 700 Duty Cycle (%) 600 RT = 1.5 k 400 300 60 50 40 30 20 RT = 10 k 7k 10 k .02 .03 .04 .05 3k 4k 5k .01 CT (F) 2k .002 .003 .005 1k .001 700 10 100 300 400 500 200 .0005 70 200 500 80 100 Frequency (kHz) 800 RT () Figure 2. Oscillator Frequency vs. CT Figure 3. Oscillator Duty Cycle vs. RT http://onsemi.com 5 CS2842A, CS3842A, CS2843A, CS3843A VREF RT A VCC 2N2222 4.7 k COMP VREF 100 k 1.0 k ERROR AMP ADJUST 4.7 k 0.1 F VFB VCC 1.0 k 1.0 W 0.1 F 5.0 k Sense ADJUST Sense VOUT OSC GND VOUT GND CT Figure 4. Test Circuit CIRCUIT DESCRIPTION OSC VCC ON/OFF Command to reset of IC CSX842A CSX843A VON 16 V 8.4 V VOFF 10 V 7.6 V OSC RESET EA Output Switch Current VCC ICC IO < 15 mA VO < 1.0 mA VCC Figure 6. Timing Diagram for Key CS2841B Parameters VON VOFF Figure 5. Typical Undervoltage Characteristics 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. 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 VCC causes the inductor current slope to increase, thus reducing the duty cycle. This is an inherent feed-forward characteristic of current mode control, since the control voltage does not have to change during changes of input supply voltage. Setting the Oscillator Oscillator timing capacitor, CT, is charged by VREF through RT 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: http://onsemi.com 6 CS2842A, CS3842A, CS2843A, CS3843A V Vlower tc RTCT ln REF VREF Vupper V IdRT Vlower td RTCT ln REF VREF IdRT Vupper VREF RT OSC 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 0.5534RTCT 2.3 0.0083RT td RTCT ln 4.0 0.0083RT CT GND Timing Parameters Vupper Vlower The frequency and maximum duty cycle can be determined using the Typical Performance Characteristic graphs. tc td Sawtooth Mode Large RT ( 10 k) Grounding VOSC High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to GND pin in a single point ground. The transistor and 5.0 k potentiometer, shown in the test circuit, are used to sample the oscillator waveform and apply and adjustable ramp to Sense. Internal Clock Triangular Mode Small RT ( 700 k) VOSC Internal Clock Figure 7. Oscillator Timing Network and Parameters http://onsemi.com 7 CS2842A, CS3842A, CS2843A, CS3843A ORDERING INFORMATION Device Temperature Range Package Shipping DIP-8 50 Units/Rail DIP-8 50 Units/Rail SO-14 55 Units/Rail CS2842ALDR14 SO-14 2500 Tape & Reel CS3842AGN8 DIP-8 50 Units/Rail CS3842AGD8 SO-8 98 Units/Rail CS3842AGDR8 SO-8 2500 Tape & Reel CS3842AGD14 SO-14 55 Units/Rail SO-14 2500 Tape & Reel CS2842ALN8 CS2843ALN8 CS2842ALD14 -25C 25C to 85C CS3842AGDR14 CS3843AGN8 0C to 70C DIP-8 50 Units/Rail CS3843AGD8 SO-8 98 Units/Rail CS3843AGDR8 SO-8 2500 Tape & Reel CS3843AGD14 SO-14 55 Units/Rail CS3843AGDR14 SO-14 2500 Tape & Reel http://onsemi.com 8 CS2842A, CS3842A, CS2843A, CS3843A PACKAGE DIMENSIONS DIP-8 N SUFFIX CASE 626-05 ISSUE L 8 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, 1982. 5 -B- 1 4 DIM A B C D F G H J K L M N F -A- NOTE 2 L C J -T- MILLIMETERS MIN MAX 9.40 10.16 6.10 6.60 3.94 4.45 0.38 0.51 1.02 1.78 2.54 BSC 0.76 1.27 0.20 0.30 2.92 3.43 7.62 BSC --10 0.76 1.01 INCHES MIN MAX 0.370 0.400 0.240 0.260 0.155 0.175 0.015 0.020 0.040 0.070 0.100 BSC 0.030 0.050 0.008 0.012 0.115 0.135 0.300 BSC --10 0.030 0.040 N SEATING PLANE D M K G H 0.13 (0.005) M T A M B M SO-8 D SUFFIX CASE 751-07 ISSUE W -X- NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION 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 0.127 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. A 8 5 0.25 (0.010) S B 1 M Y M 4 K -Y- G C N X 45 SEATING PLANE -Z- 0.10 (0.004) H D 0.25 (0.010) M Z Y S X M S http://onsemi.com 9 J DIM A B C D G H J K M N S MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 BSC 0.10 0.25 0.19 0.25 0.40 1.27 0 8 0.25 0.50 5.80 6.20 INCHES MIN MAX 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 BSC 0.004 0.010 0.007 0.010 0.016 0.050 0 8 0.010 0.020 0.228 0.244 CS2842A, CS3842A, CS2843A, CS3843A PACKAGE DIMENSIONS SO-14 D SUFFIX CASE 751A-03 ISSUE F NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. 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 0.127 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. -A- 14 8 -B- 1 P 7 PL 0.25 (0.010) 7 G M B M F R X 45 C -T- SEATING PLANE D 14 PL 0.25 (0.010) M T B J M K S A S http://onsemi.com 10 DIM A B C D F G J K M P R MILLIMETERS MIN MAX 8.55 8.75 3.80 4.00 1.35 1.75 0.35 0.49 0.40 1.25 1.27 BSC 0.19 0.25 0.10 0.25 0 7 5.80 6.20 0.25 0.50 INCHES MIN MAX 0.337 0.344 0.150 0.157 0.054 0.068 0.014 0.019 0.016 0.049 0.050 BSC 0.008 0.009 0.004 0.009 0 7 0.228 0.244 0.010 0.019 CS2842A, CS3842A, CS2843A, CS3843A Notes http://onsemi.com 11 CS2842A, CS3842A, CS2843A, CS3843A ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. 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