CS2842A CHERRY | Alldatasheet

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Features

S R PWM Latch Current Sensing Comparator Oscillator 1 VR 2 R VCError Amplifier 2.50V Set/ Reset Undervoltage Lock-out Circuit 34V ( ) Indicates CS-2843A/3843A 16V/10V (8.4V/7.6V) VCC Pwr Pwr Gnd I Optimized for Off-line Control I Internally Trimmed Temperature Compensated Oscillator I Maximum Duty-cycle Clamp I V REF stabilized before Output Stage is Enabled I Low Start-up Current I Pulse-by-pulse Current Limiting I Improved Undervoltage Lockout I Double Pulse Suppression I 1% Trimmed Bandgap Reference I High Current Totem Pole Output Package Options CS2842A/3843A SERIES Off-Line Current Mode PWM ControlCircuit with Undervoltage Lockout CS2842A/CS3842A CS2843A/CS3843A

Description

Analog Inputs (V Lead Temperature Soldering 1COMP VFB Sense OSC VREF VCC VOUT Gnd

8 Lead PDIP & SO Narrow

14 Lead SO Narrow

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 varia- tions 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 V REF is stabilized before the output stage is enabled. Ion implant resistors provide tighter con- trol of undervoltage lockout. Other features include low start-up current, pulse-by-pulse current limit- ing, and a high-current totem pole out- put for driving capacitive loads, such as the gate of power MOSFET. The out- put 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. A Company ® Rev. 10/23/98 Cherry Semiconductor Corporation

2000 South County Trail, East Greenwich, RI 02818

Tel: (401)885-3600 Fax: (401)885-5786 Email: info@cherry-semi.com Web Site: www.cherry-semi.com

RT = 680Ω, CT = .022µF for triangular mode, RT = 10kΩ, CT = 3.3nF for sawtooth mode (see Figure 3), unless otherwise stated. CS2842A/CS2843A CS3842A/CS3843A PARAMETER TEST CONDITIONS MIN TYP MAX MIN TYP MAX UNITS CS2842A/3843A SERIES I Reference Section Line Regulation 12 ≤ VIN ≤ 25V 6 20 6 20 mV Load Regulation 1 ≤ IOUT ≤ 20mA 6 25 6 25 mV Temperature Stability (Note 2) 0.2 0.4 0.2 0.4 mV / ˚C Output Noise Voltage 10Hz ≤ f ≤ 10kHz, T J = 25˚C (Note 2) 50 50 µV Long Term Stability T A = 125˚C, 1kHrs. (Note 2) 5 25 5 25 mV Output Short Circuit T A = 25˚C -30 -100 -180 -30 -100 -180 mA I Oscillator Section Initial Accuracy Sawtooth Mode (see Fig. 3), T J = 25˚C 4 75 25 74 75 25 7 k H z Triangular Mode (see Fig. 3), TJ = 25˚C 4 75 25 74 45 26 0 k H z Voltage Stability 12 ≤ VCC ≤ 25V 0.2 1.0 0.2 1.0 % Temp. Stability Sawtooth Mode T MIN ≤ TA ≤ TMAX (Note 2) 5 5 % Triangular Mode TMIN ≤ TA ≤ TMAX (Note 2) 8 8 % Amplitude OSC peak to peak 1.7 1.7 V Discharge Current T TMIN ≤ TA ≤ TMAX 7.2 9.5 7.2 9.5 mA I Error Amp Section Input Bias Current V FB = 0 -0.3 -1.0 -0.3 -2.0 µA AVOL 2 ≤ VOUT ≤ 4V 65 90 65 90 dB Unity Gain Bandwidth (Note 2) 0.7 1.0 0.7 1.0 MHz PSRR 12 ≤ V CC ≤ 25V 60 70 60 70 dB Output Sink Current V FB = 2.7V, VCOMP = 1.1V 2 6 2 6 mA VOUT High V FB = 2.3V, RL = 15kΩ to ground 5 6 5 6 V I Current Sense Section Maximum Input Signal V PSRR 12 ≤ VCC ≤ 25V (Note 3) 70 70 dB Input Bias Current V Sense = 0 -2 -10 -2 -10 µA Delay to Output T J = 25˚C (Note 2) 150 300 150 300 ns I Output Section Output Low Level I SINK = 20mA 0.1 0.4 0.1 0.4 V ISINK = 200mA 1.5 2.2 1.5 2.2 V Output High Level I SOURCE = 20mA 13.0 13.5 13.0 13.5 V ISOURCE = 200mA 12.0 13.5 12.0 13.5 V

Electrical Characteristics: continued CS2842A/CS2843A CS3842A/CS3843A PARAMETER TEST CONDITIONS MIN TYP MAX MIN TYP MAX UNITS CS2842A CS3842A CS2843A/CS3843A PARAMETER TEST CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS Notes: 1. Adjust VCC above the start threshold before setting at 15V. 3. Parameter measured at trip point of latch with VFB=0. 2.These parameters, although guaranteed, are not 100% tested in production. 4. Gain defined as: A = ; 0 ≤ VSense ≤ 0.8V. ∆VCOMP ∆VSense I Under-Voltage Lockout Section Voltage I Output Section: continued Rise Time T J = 25˚C, CL = 1nF (Note 2) 50 150 50 150 ns Fall Time T J = 25˚C, CL = 1nF (Note 2) 50 150 50 150 ns Output Leakage UVLO Active, V OUT = 0 -0.01 -10.00 -0.01 -10.00 µA I Total Standby Current Start-Up Current 0.5 1.0 0.5 1.0 mA Operating Supply Current V FB = VSense = 0V, RT = 10kΩ, CT = 3.3nF 11 17 11 17 mA VCC Zener Voltage I CC = 25mA 34 34 V Package Pin Description PACKAGE PIN # PIN SYMBOL FUNCTION 8L PDIP/SO 14L SO Narrow 1 1 COMP Error amp output, used to compensate error amplifier 23 V FB Error amp inverting input 3 5 Sense Noninverting input to Current Sense Comparator 4 7 OSC Oscillator timing network with Capacitor to Ground, resistor to V REF 5 8 Gnd Ground

9 Pwr Gnd Output driver Ground

61 0 V OUT Output drive pin

11 V CCPwr Output driver positive supply

71 2V CC Positive power supply 81 4V REF Output of 5V internal reference 2,4,6,13 NC No Connection

1k Ω 0.1 µF 0.1 µF VREF VCC VOUT Gnd VFB Sense OSC COMP 5k Ω 100k Ω 4.7k Ω 1k Ω ERROR AMP ADJUST 4.7k Ω Sense ADJUST RT 2N2222 CT Gnd A Test Circuit Undervoltage Lockout During Undervoltage Lockout (Figure 1), the output driv- er 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 2). An increase in V CC 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. When the power supply sees a sudden large output cur- rent 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 trans- VCC ON/OFF Command to reset of IC VON 16V 8.4V VOFF 10V 7.6V CSX842A CSX843A <15mA <1mA VON VOFF ICC VCC Circuit Description Typical Performance Characteristics 800 900FREQ. (kHz) CT (µF) 700 600 500 400 300 200 100 .05 RT =1.5kΩ RT =680Ω RT =10kΩ 100 200 700 1k 2k 5k 7k 10k DUTY CYCLE (%) RT (Ω) 4k3k500400300 100 Oscillator Duty Cycle vs RTOscillator Frequency vs CT Figure 1: Typical Undervoltage Characteristics

RΘJC typ 52 45 30 ˚C/W RΘJA typ 100 165 125 ˚C/W

Ordering Information

Part Number 0 ˚C to -25 ˚C to Description 70˚C8 5 ˚C CS2842ALN8  8L PDIP CS2843ALN8  8L PDIP CS3842AGN8  8L PDIP CS3842AGD8  8L SO Narrow CS3842AGDR8  8L SO Narrow (tape & reel) CS3842AGD14  14L SO Narrow CS3842AGDR14  14L SO Narrow (tape & reel) CS2843ALD14  14L SO Narrow CS2843ALDR14  14L SO Narrow (tape & reel) CS3843AGN8  8L PDIP CS3843AGD8  8L SO Narrow CS3843AGDR8  8L SO Narrow (tape & reel) CS3843AGD14  14L SO Narrow CS3843AGDR14  14L SO Narrow (tape & reel) Rev. 10/23/98 CS2842A/3843A SERIES D Lead Count Metric English Max Min Max Min 8 Lead PDIP 10.16 9.02 .400 .355 8 Lead SO Narrow 5.00 4.80 .197 .189 14 Lead SO Narrow 8.75 8.55 .344 .337 Package Specification PACKAGE DIMENSIONS IN mm (INCHES) PACKAGE THERMAL DATA © 1999 Cherry Semiconductor Corporation Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information. Plastic DIP (N); 300 mil wide 0.39 (.015) MIN. 1.14 (.045) D Some 8 and 16 lead packages may have 1/2 lead at the end of the package. All specs are the same. .203 (.008) .356 (.014) REF: JEDEC MS-001 3.68 (.145) 2.92 (.115) 8.26 (.325) 7.62 (.300) 7.11 (.280) 6.10 (.240) .356 (.014) .558 (.022) Surface Mount Narrow Body (D); 150 mil wide 0.33 (.013) 6.20 (.244) 5.80 (.228) 4.00 (.157) 3.80 (.150) 1.57 (.062) 1.37 (.054) D 0.25 (0.10) 0.10 (.004) 1.75 (.069) MAX 1.27 (.050) 0.40 (.016) REF: JEDEC MS-012 0.25 (.010) 0.19 (.008)