CS2844, CS3844, CS2845, CS3845 Current Mode PWM Control Circuit with 50% Max Duty Cycle The CS3844/45 provides all the necessary features to implement off–line fixed frequency current–mode control with a minimum number of external components. The CS3844 family incorporates a new precision temperature–controlled oscillator to minimize variations in frequency. An internal toggle flip–flop, which blanks the output every other clock cycle, limits the duty–cycle range to less than 50%. An undervoltage lockout ensures that VREF is stabilized before the output stage is enabled. In the CS2844/CS3844 turn on occurs at 16 V and turn off at 10 V. In the CS2845/CS3845 turn on is at 8.4 V and turn off at 7.6 V. Other features include low start–up current, pulse–by–pulse current limiting, and a high–current totem pole output for driving capacitive loads, such as gate of a power MOSFET. The output is low in the off state, consistent with N–channel devices. http://onsemi.com MARKING DIAGRAMS 8 CSx84yN AWL YYWW DIP–8 N SUFFIX CASE 626 8 1 8 1 8 1 SO–8 D SUFFIX CASE 751 384yD ALYW 1 14 Features • Optimized for Off–Line Control • Temp. Compensated Oscillator • 50% Max Duty–Cycle Clamp • VREF Stabilized Before Output Stage Is Enabled • Low Start–Up Current • Pulse–By–Pulse Current Limiting • Improved Undervoltage Lockout • Double Pulse Suppression • 1.0% Trimmed Bandgap Reference • High Current Totem Pole Output SO–14 D SUFFIX CASE 751A 14 1 CSx84yD14 AWLYWW 1 16 SO–16L DW SUFFIX CASE 751G 16 CSx84yDW AWLYYWW 1 1 x y A WL, L YY, Y WW, W = 2 or 3 = 4 or 5 = Assembly Location = Wafer Lot = Year = Work Week ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 7 of this data sheet. Semiconductor Components Industries, LLC, 2001 June, 2001 – Rev. 3 1 Publication Order Number: CS2844/D CS2844, CS3844, CS2845, CS3845 PIN CONNECTIONS DIP–8 & SO–8 COMP 1 8 SO–14 1 COMP NC VFB NC Sense NC OSC VREF VCC VFB Sense OSC SO–16L 14 VOUT GND 1 VREF NC VCC VCC Pwr VOUT GND Pwr GND 16 NC VREF VCC VCC Pwr VOUT GND Pwr GND NC NC NC COMP VFB Sense OSC NC NC VCC Undervoltage Lockout VCC VCC Pwr 34 V Set/ Reset GND 5.0 V Reference 16 V/10 V (8.4 V/7.6 V) Error Amplifier COMP Internal Bias – VFB VREF R VREF Undervoltage Lockout + 2.50 V R Toggle Flip–Flop OSC NOR Oscillator VOUT S 2R R R 1.0 V PWM Latch Current Sensing Comparator Sense ( ) Indicates CS2845/3845 Figure 1. Block Diagram http://onsemi.com 2 Pwr GND CS2844, CS3844, CS2845, CS3845 MAXIMUM RATINGS* Rating Value Unit Self Limiting – 30 V Output Current ±1.0 A Output Energy (Capacitive Load) 5.0 µJ –0.3 to + 5.5 V Error Amp Output Sink Current 10 mA Package Thermal Resistance, PDIP–8 Junction–to–Case, RθJC Junction–to–Ambient, RθJA 52 100 °CW °CW Package Thermal Resistance, SO–8 Junction–to–Case, RθJC Junction–to–Ambient, RθJA 45 165 °CW °CW Package Thermal Resistance, SO–14 Junction–to–Case, RθJC Junction–to–Ambient, RθJA 30 125 °CW °CW Package Thermal Resistance, SO–16L Junction–to–Case, RθJC Junction–to–Ambient, RθJA 23 105 °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 183°C. *The maximum package power dissipation must be observed. ELECTRICAL CHARACTERISTICS (–25° ≤ TA ≤ 85° for CS2844/2845, 0° ≤ TA ≤ 70° for CS3844/CS3845. VCC = 15 V*; RT = 10 kΩ, CT = 3.3 nF for sawtooth mode; unless otherwise stated.) CS2844/CS2845 Characteristic Test Conditions CS3844/CS3845 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 = 25°C, IREF = 1.0 mA Line Regulation 12 ≤ VCC ≤ 25 V – 6.0 20 – 6.0 20 mV Load Regulation 1.0 ≤ IREF ≤ 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 = 25°C. Note 3. – 50 – – 50 – µV Long Term Stability TA = 125°C, 1000 Hrs. Note 3. – 5.0 25 – 5.0 25 mV Output Short Circuit TA = 25°C –30 –100 –180 –30 –100 –180 mA Initial Accuracy Sawtooth Mode, TJ = 25°C 47 52 57 47 52 57 kHz Voltage Stability 12 ≤ VCC ≤ 25 V – 0.2 1.0 – 0.2 1.0 % Temperature Stability Sawtooth Mode TMIN ≤ TA ≤ TMAX. Note 3. – 5.0 – – 5.0 – % Amplitude VOSC (peak to peak) – 1.7 – – 1.7 – V 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 CS2844, CS3844, CS2845, CS3845 ELECTRICAL CHARACTERISTICS (continued) (–25° ≤ TA ≤ 85° for CS2844/2845, 0° ≤ TA ≤ 70° for CS3844/CS3845. VCC = 15 V*; RT = 10 kΩ, CT = 3.3 nF for sawtooth mode; 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 µA 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, RL = 15 kΩ to GND 5.0 6.0 – 5.0 6.0 – V VOUT Low VFB = 2.7 V, RL = 15 kΩ 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 µA Delay to Output TJ = 25°C. 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 = 25°C, CL = 1.0 nF. Note 4. – 50 150 – 50 150 ns Fall Time TJ = 25°C, CL = 1.0 nF. Note 4. – 50 150 – 50 150 ns – 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 kΩ, CT = 3.3 nF – 11 17 – 11 17 mA VCC Zener Voltage ICC = 25 mA – 34 – – 34 – V PWM Section Maximum Duty Cycle – 46 48 50 46 48 50 % Minimum Duty Cycle – – – 0 – – 0 % 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 CS2844, CS3844, CS2845, CS3845 ELECTRICAL CHARACTERISTICS (continued) (–25° ≤ TA ≤ 85° for CS2844/2845, 0° ≤ TA ≤ 70° for CS3844/CS3845. VCC = 15 V*; RT = 10 kΩ, CT = 3.3 nF for sawtooth mode; unless otherwise stated.) CS2844 Characteristic Test Conditions CS3844 CS2845/CS3845 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 DIP–8 & SO–8 SO–14 Symbol Symbol 1 1 3 COMP 2 3 4 VFB 3 5 5 Sense 4 7 6 OSC Oscillator timing network with capacitor to ground, resistor to VREF. 5 9 11 GND Ground. – 8 10 Pwr GND 6 10 12 VOUT – 11 13 VCC Pwr 7 12 14 VCC Positive power supply. Output of 5.0 V internal reference. 8 14 15 VREF – 2, 4, 6, 13 1, 2, 7, 8, 9, 16 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. VREF RT A VCC 2N2222 4.7 kΩ COMP VREF 100 kΩ 1.0 kΩ ERROR AMP ADJUST 4.7 kΩ 0.1 µF VFB 5.0 kΩ Sense ADJUST VCC 1.0 kΩ 1.0 W 0.1 µF Sense VOUT OSC GND VOUT GND CT Figure 2. Test Circuit Open Loop Laboratory Test Fixture http://onsemi.com 5 CS2844, CS3844, CS2845, CS3845 CIRCUIT DESCRIPTION Vupper VCC ON/OFF Command to reset of IC Vlower VON VOFF CSX844 CSX845 16 V 8.4 V 10 V ton toff td tc 7.6 V ton = tc toff = tc + 2td ICC Figure 5. Duty Cycle Parameters < 15 mA 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 OSC components. < 1.0 mA VCC VON VOFF Figure 3. Startup Voltage for CSX844 and CSX845 Undervoltage Lockout During Undervoltage Lockout (Figure 3), the output driver is biased to sink minor amounts of current. The output should be shunted to ground with a resistor to prevent activating the power switch with extraneous leakage currents. Setting the Oscillator The times tc and td can be determined as follows: V Vlower tc RTCT ln REF VREF Vupper 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 4). 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. V IdRT Vlower td RTCT ln REF VREF IdRT Vupper 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 then: tc 0.5534RTCT 2.3 0.0083RT td RTCT ln 4.0 0.0083RT VOSC For better accuracy RT should be ≥ 10 kΩ. OSC RESET Grounding Toggle F/F Output High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to Gnd in a single point ground. The transistor and 5.0 kΩ potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to Sense. EA Output Switch Current VCC IO VO Figure 4. Timing Diagram http://onsemi.com 6 CS2844, CS3844, CS2845, CS3845 ORDERING INFORMATION Device Temperature Range Package Shipping CS2844LN8 DIP–8 50 Units/Rail CS2844LD14 SO–14 55 Units/Rail CS2844LDR14 SO–14 2500 Tape & Reel CS2844LDW16 SO–16L 48 Units/Rail SO–16L 2500 Tape & Reel DIP–8 50 Units/Rail CS2845LDW16 SO–16L 48 Units/Rail CS2845LDWR16 SO–16L 2500 Tape & Reel CS3844GN8 DIP–8 50 Units/Rail CS3844GD8 SO–8 98 Units/Rail CS3844GDR8 SO–8 2500 Tape & Reel CS3844GD14 SO–14 55 Units/Rail CS3844GDR14 SO–14 2500 Tape & Reel CS3844GDW16 SO–16 48 Units/Rail SO–16 2500 Tape & Reel CS2844LDWR16 –25°C 25°C to 85°C CS2845LN8 CS3844GDWR16 CS3845GN8 0°C to 70°C DIP–8 50 Units/Rail CS3845GD8 SO–8 98 Units/Rail CS3845GDR8 SO–8 2500 Tape & Reel CS3845GD14 SO–14 55 Units/Rail CS3845GDR14 SO–14 2500 Tape & Reel CS3845GDW16 SO–16L 48 Units/Rail CS3845GDWR16 SO–16L 2500 Tape & Reel http://onsemi.com 7 CS2844, CS3844, CS2845, CS3845 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 8 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 CS2844, CS3844, CS2845, CS3845 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 M T B J M K D 14 PL 0.25 (0.010) S A S 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 SO–16L DW SUFFIX CASE 751G–03 ISSUE B A D 9 1 8 NOTES: 1. DIMENSIONS ARE IN MILLIMETERS. 2. INTERPRET DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. 3. DIMENSIONS D AND E DO NOT INLCUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE. 5. DIMENSION B DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.13 TOTAL IN EXCESS OF THE B DIMENSION AT MAXIMUM MATERIAL CONDITION. 16X M 14X e T A S B h X 45 S L A 0.25 B B A1 H E 0.25 8X M B M 16 SEATING PLANE T C http://onsemi.com 9 DIM A A1 B C D E e H h L MILLIMETERS MIN MAX 2.35 2.65 0.10 0.25 0.35 0.49 0.23 0.32 10.15 10.45 7.40 7.60 1.27 BSC 10.05 10.55 0.25 0.75 0.50 0.90 0 7 CS2844, CS3844, CS2845, CS3845 Notes http://onsemi.com 10 CS2844, CS3844, CS2845, CS3845 Notes http://onsemi.com 11 CS2844, CS3844, CS2845, CS3845 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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