UC1846/7 UC2846/7 UC3846/7 Current Mode PWM Controller FEATURES • DESCRIPTION Automatic Feed Forward Compensation • The UC1846/7 family of control ICs provides all of the necessary features to implement fixed frequency, current mode control Programmable Pulse-by-Pulse Current schemes while maintaining a minimum external parts count. The suLimiting perior performance of this technique can be measured in improved Automatic Symmetry Correction in Push-pull line regulation, enhanced load response characteristics, and a simConfiguration pler, easier-to-design control loop. Topological advantages include inherent pulse-by-pulse current limiting capability, automatic symEnhanced Load Response Characteristics metry correction for push-pull converters, and the ability to parallel Parallel Operation Capability for Modular “power modules" while maintaining equal current sharing. Power Systems Protection circuitry includes built-in under-voltage lockout and proDifferential Current Sense Amplifier with grammable current limit in addition to soft start capability. A shutWide Common Mode Range down function is also available which can initiate either a complete shutdown with automatic restart or latch the supply off. Double Pulse Suppression • 500mA (Peak) Totem-pole Outputs • ±1% Bandgap Reference • Under-voltage Lockout • Soft Start Capability • Shutdown Terminal • 500kHZ Operation • • • • • BLOCK DIAGRAM 1/97 Other features include fully latched operation, double pulse suppression, deadline adjust capability, and a ±1% trimmed bandgap reference. The UC1846 features low outputs in the OFF state, while the UC1847 features high outputs in the OFF state. UC1846/7 UC2846/7 UC3846/7 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (Pin 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V Collector Supply Voltage (Pin 13). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V Output Current, Source or Sink (Pins 11, 14). . . . . . . . . . . . . . . . . . . . . . . . 500mA Analog Inputs (Pins 3, 4, 5, 6, 16) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +VIN Reference Output Current (Pin 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30mA Sync Output Current (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA Error Amplifier Output Current (Pin 7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA Soft Start Sink Current (Pin 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA Oscillator Charging Current (Pin 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA Power Dissipation at TA=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW Power Dissipation at TC=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000mW Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65°C to +150°C Lead Temperature (soldering, 10 seconds. . . . . . . . . . . . . . . . . . . . . . . . . +300°C Note 1. All voltages are with respect to Ground, Pin 13. Currents are positive into, negative out of the speficied terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages. Pin numbers refer to DIL and SOIC packages only. CONNECTION DIAGRAMS DIL-16, SOIC-16 (TOP VIEW) J or N Package, DW Package PLCC-20, LCC-20 (TOP VIEW) Q, L Packages PACKAGE PIN FUNCTION FUNCTION PIN 1 N/C 2 C/L SS 3 VREF 4 C/S5 C/S+ 6 N/C 7 E/A+ 8 E/A9 Comp 10 CT 11 N/C 12 RT 13 Sync 14 A Out 15 Gnd 16 N/C 17 VC 18 B Out 19 VIN 20 Shutdown ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15V, RT=10k, CT=4.7nF, TA=TJ.) UC1846/UC1847 PARAMETER TEST CONDITIONS UC2846/UC2847 UC3846/UC3847 MIN. TYP. MAX. MIN. TYP. MAX. UNITS 5.05 5.10 5.15 5.00 5.10 5.20 V Reference Section Output Voltage TJ=25°C, IO=1mA Line Regulation VIN=8V to 40V 5 20 5 20 mV Load Regulation IL=1mA to 10mA 3 15 3 15 mV Temperature Stability Over Operating Range, (Note 2) Total Output Variation Line, Load, and Temperature (Note 2) 0.4 Output Noise Voltage 10Hz≤ f ≤10kHz, TJ=25°C (Note 2) Long Term Stability TJ=125°C, 1000 Hrs. (Note 2) Short Circuit Output Current VREF=0V 5.00 -10 2 0.4 5.20 4.95 mV/°C 5.25 V 100 100 µV 5 5 mV -45 mA -45 -10 UC1846/7 UC2846/7 UC3846/7 (Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C ELECTRICAL CHARACTERISTICS (cont.) to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15V, RT=10k, CT=4.7nF, TA=TJ.) UC1846/UC1847 PARAMETER TEST CONDITIONS UC2846/UC2847 UC3846/UC3847 MIN. TYP. MAX. MIN. TYP. MAX. UNITS 39 43 47 39 43 47 2 -1 2 Oscillator Section Initial Accuracy TJ=25°C Voltage Stability VIN=8V to 40V -1 Temperature Stability Over Operating Range (Note 2) -1 Sync Output High Level 3.9 Sync Output Low Level 4.35 2.3 Sync Input High Level Pin 8=0V Sync Input Low Level Pin 8=0V Sync Input Current Sync Voltage=3.9V, Pin 8=0V -1 3.9 2.5 3.9 % % 4.35 2.3 kHz V 2.5 V 2.5 V 3.9 V 2.5 1.3 1.5 1.3 1.5 mA Input Offset Voltage 0.5 5 0.5 10 mV Input Bias Current -0.6 -1 -0.6 -2 µA Input Offset Current 40 250 40 250 nA Error Amp Section Common Mode Range VIN=8V to 40V 0 Open Loop Voltage Gain ∆VO=1.2 to 3V, VCM=2V 80 Unity Gain Bandwidth TJ=25°C (Note 2) CMRR VCM=0V to 38V, VIN=40V VIN-2V 0 105 80 0.7 1.0 75 100 VIN-2V V 105 dB 0.7 1.0 MHz 75 100 dB PSRR VIN=8V to 40V 80 105 80 105 dB Output Sink Current VID=-15mV to -5V, VPIN 7=1.2V 2 6 2 6 mA Output Source Current VID=15mV to 5V, VPIN 7=2.5V -0.4 -0.5 -0.4 -0.5 mA High Level Output Voltage RL=(Pin 7) 15kΩ 4.3 4.6 4.3 4.6 V Low Level Output Voltage 0.7 1 2.5 2.75 3.0 1.1 1.2 0.7 1 V 2.5 2.75 3.0 V 1.1 1.2 25 mV Current Sense Amplifier Section Amplifier Gain VPIN 3=0V, Pin 1 Open (Notes 3 & 4) Maximum Differential Input Pin 1 Open (Note 3) Signal (VPIN 4-VPIN 3) RL (Pin 7)=15kW Input Offset Voltage VPIN 1=0.5V, Pin 7 Open (Note 3) CMRR VCM=1V to 12V 60 60 PSRR VIN=8V to 40V Input Bias Current VPIN 1=0.5V, Pin 7 Open (Note 3) Input Offset Current VPIN 1=0.5V, Pin 7 Open (Note 3) Input Common Mode Range Delay to Outputs 5 83 0.08 60 -10 0.5 0.55 -10 -30 350 400 250 VIN 0 dB -10 µA 1 µA VIN-3 V 200 500 ns 0.5 0.55 V -10 -30 µA 350 400 mV VIN V 0.08 500 dB 84 0 200 V 83 -2.5 1 VIN-3 0 5 60 84 -2.5 TJ=25°C, (Note 2) 25 Current Limit Adjust Section Current Limit Offset VPIN 3=0V, VPIN 4=0V, Pin 7 Open (Note 3) Input Bias Current 0.45 VPIN 5=VREF, VPIN 6=0V 0.45 Shutdown Terminal Section Threshold Voltage 250 Input Voltage Range Minimum Latching Current 0 (Note 6) (IPIN 1) 3.0 3 1.5 3.0 1.5 mA UC1846/7 UC2846/7 UC3846/7 (Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C ELECTRICAL CHARACTERISTICS (cont.) to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15V, RT=10k, CT=4.7nF, TA=TJ.) UC1846/UC1847 PARAMETER TEST CONDITIONS UC2846/UC2847 MIN. TYP. MAX. UC3846/UC3847 MIN. TYP. MAX. UNITS Shutdown Terminal Section (cont.) Maximum Non-Latching (Note 7) Current (IPIN 1) Delay to Outputs TJ=25°C (Note 2) 1.5 0.8 1.5 0.8 mA 300 600 300 600 ns Output Section Collector-Emitter Voltage 40 Collector Leakage Current VC=40V (Note 5) Output Low Level ISINK=20mA V 200 µA 0.1 0.4 V 0.4 2.1 V 200 ISINK=100mA Output High Level 40 0.1 0.4 0.4 2.1 ISOURCE=20mA 13 13.5 ISOURCE=100mA 12 13.5 13 13.5 12 13.5 V V Rise Time CL=1nF, TJ=25°C (Note 2) 50 300 50 300 ns Fall Time CL=1nF, TJ=25°C (Note 2) 50 300 50 300 ns Start-Up Threshold 7.7 8.0 7.7 8.0 V Threshold Hysteresis 0.75 Under-Voltage Lockout Section 0.75 V Total Standby Current Supply Current 17 21 17 21 mA Note 2. These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production. Note 3. Parameter measured at trip point of latch with VPIN 5 = VREF, VPIN 6 = 0V. ∆ VPIN 7 ; ∆ VPIN 4 = 0 to 1.0V. Note 4. Amplifier gain defined as: G= ∆ VPIN 4 Note 5. Applies to UC1846/UC2846/UC3846 only due to polarity of outputs. Note 6. Current into Pin 1 guaranteed to latch circuit in shutdown state. Note 7. Current into Pin 1 guaranteed not to latch circuit in shutdown state. APPLICATIONS DATA Oscillator Circuit ID Output deadtime is determined by the external capacitor, CT, according to the formula: τd (µs) = 145CT (µf ) . ID − 3.6 ID = Oscillator discharge current at 25°C is typically 7.5. RT (kΩ) For large values of RT: τd (µs) ≈ 145CT (µf ). 2.2 Oscillator frequency is approximated by the formula: fT (kHz) ≈ . RT (kΩ)• CT (µf ) 4 UC1846/7 UC2846/7 UC3846/7 APPLICATIONS DATA (cont.) Error Amp Gain and Phase vs Frequency Error Amp Output Configuration Error Amp Open-Logic D.C. Gain vs Load Resistance Parallel Operation 5 UC1846/7 UC2846/7 UC3846/7 APPLICATIONS DATA (cont.) Pulse by Pulse Current Limiting R2 VREF − 0.5 R1 + R2 Peak Current (IS) is determined by the formula: IS = 3RS Soft Start and Shutdown /Restart Functions 6 UC1846/7 UC2846/7 UC3846/7 APPLICATIONS DATA (cont.) Current Sense Amp Connection A small RC filter may be required in some applications to reduce switch transients. Differential input allows remote, noise free sensing. UC1846 Open Loop Test Circuit UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603)424-3460 7 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 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