UC1525A/27AUC2525A/27AUC3525A/27ARegulating Pulse Width ModulatorsFEATURES• 8 to 35V Operation• 5.1V Reference Trimmed to±1%• 100Hz to 500kHz OscillatorRange• Separate Oscillator SyncTerminal• Adjustable Deadtime Control• Internal Soft-Start• Pulse-by-Pulse Shutdown• Input Undervoltage Lockoutwith Hysteresis• Latching PWM to PreventMultiple Pulses• Dual Source/Sink OutputDriversDESCRIPTIONThe UC1525A/1527A series of pulse width modulator integrated circuits are de-signed to offer improved performance and lowered external parts count when usedin designing all types of switching power supplies. The on-chip +5.1V reference istrimmed to ±1% and the input common-mode range of the error amplifier includesthe reference voltage, eliminating external resistors. A sync input to the oscillatorallows multiple units to be slaved or a single unit to be synchronized to an externalsystem clock. A single resistor between the CT and the discharge terminals pro-vides a wide range of dead-time adjustment. These devices also feature built-insoft-start circuitry with only an external timing capacitor required. A shutdown termi-nal controls both the soft-start circuitry and the output stages, providing instantane-ous turn off through the PWM latch with pulsed shutdown, as well as soft-startrecycle with longer shutdown commands. These functions are also controlled byan undervoltage lockout which keeps the outputs off and the soft-start capacitordischarged for sub-normal input voltages. This lockout circuitry includes approxi-mately 500mV of hysteresis for jitter-free operation. Another feature of these PWMcircuits is a latch following the comparator. Once a PWM pulse has been termi-nated for any reason, the outputs will remain off for the duration of the period. Thelatch is reset with each clock pulse. The output stages are totem-pole designs ca-pable of sourcing or sinking in excess of 200mA. The UC1525A output stage fea-tures NOR logic, giving a LOW output for an OFF state. The UC1527A utilizes ORlogic which results in a HIGH output level when OFF.BLOCK DIAGRAM2/96ABSOLUTE MAXIMUM RATINGS (Note 1)Supply Voltage, (+VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40VCollector Supply Voltage (VC) . . . . . . . . . . . . . . . . . . . . . . +40VLogic Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +5.5VAnalog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +VINOutput Current, Source or Sink . . . . . . . . . . . . . . . . . . . 500mAReference Output Current . . . . . . . . . . . . . . . . . . . . . . . . 50mAOscillator Charging Current . . . . . . . . . . . . . . . . . . . . . . . . 5mAPower Dissipation at TA = +25°C (Note 2) . . . . . . . . . . 1000mWPower Dissipation at TC = +25°C (Note 2). . . . . . . . . . 2000mWOperating Junction Temperature . . . . . . . . . . . -55°C to +150°CStorage Temperature Range . . . . . . . . . . . . . . -65°C to +150°CLead Temperature (Soldering, 10 seconds). . . . . . . . . . +300°CNote 1: Values beyond which damage may occur.Note 2: Consult packaging Section of Databook for thermallimitations and considerations of package.UC1525A/27AUC2525A/27AUC3525A/27ARECOMMENDED OPERATING CONDITIONS(Note 3)Input Voltage (+VIN) . . . . . . . . . . . . . . . . . . . . . . . . +8V to +35VCollector Supply Voltage (VC) . . . . . . . . . . . . . . +4.5V to +35VSink/Source Load Current (steady state) . . . . . . . . 0 to 100mASink/Source Load Current (peak). . . . . . . . . . . . . . 0 to 400mAReference Load Current. . . . . . . . . . . . . . . . . . . . . . 0 to 20mAOscillator Frequency Range. . . . . . . . . . . . . . 100Hz to 400kHzOscillator Timing Resistor. . . . . . . . . . . . . . . . . . . 2kΩ to 150kΩOscillator Timing Capacitor. . . . . . . . . . . . . . . . .001µF to 0.1µFDead Time Resistor Range . . . . . . . . . . . . . . . . . . . . 0 to 500ΩOperating Ambient Temperature Range UC1525A, UC1527A. . . . . . . . . . . . . . . . . . -55°C to +125°C UC2525A, UC2527A. . . . . . . . . . . . . . . . . . . -25°C to +85°C UC3525A, UC3527A. . . . . . . . . . . . . . . . . . . . . 0°C to +70°CNote 3: Range over which the device is functional andparameter limits are guaranteed.CONNECTION DIAGRAMSDIL-16 (TOP VIEW)J or N PackagePLCC-20, LCC-20 (TOP VIEW)Q, L PackagePACKAGE PIN FUNCTIONFUNCTION PINN/C 1Inv. Input 2N.I. Input 3SYNC 4OSC. output 5N/C 6CT 7RT 8Discharge 9Softstart 10N/C 11Compensation 12Shutdown 13Output A 14Ground 15N/C 16VC 17Output B 18+VIN 19VREF 202ELECTRICAL CHARACTERISTICS:PARAMETER TEST CONDITIONSUC1525A/UC2525AUC1527A/UC2527AUC3525AUC3527AUNITSMIN TYP MAX MIN TYP MAXReference SectionOutput Voltage TJ = 25°C 5.05 5.10 5.15 5.00 5.10 5.20 VLine Regulation VIN = 8 to 35V 10 20 10 20 mVLoad Regulation IL = 0 to 20mA 20 50 20 50 mVTemperature Stability (Note 5) Over Operating Range 20 50 20 50Total Output Variation (Note 5) Line, Load, and Temperature 5.00 5.20 4.95 5.25 VShorter Circuit Current VREF = 0, TJ = 25°C 80 100 80 100 mAOutput Noise Voltage (Note 5) 10Hz ≤ 10kHz, TJ = 25°C 40 200 40 200 µVrmsLong Term Stability (Note 5) TJ = 125°C 20 50 20 50 mVOscillator Section (Note 6)Initial Accuracy (Notes 5 & 6) TJ = 25°C ± 2 ± 6 ± 2 ± 6%Voltage Stability (Notes 5 & 6) VIN = 8 to 35V ± 0.3 ± 1 ± 1 ± 2%Temperature Stability (Note 5) Over Operating Range ± 3 ± 6 ± 3 ± 6%Minimum Frequency RT = 200kΩΩ, CT = 0.1µµF120120HzMaximum Frequency RT = 2kΩΩ, CT = 470pF 400 400 kHzCurrent Mirror IRT = 2mA 1.7 2.0 2.2 1.7 2.0 2.2 mAClock Amplitude (Notes 5 & 6) 3.0 3.5 3.0 3.5 VClock Width (Notes 5 & 6) TJ = 25°C 0.3 0.5 1.0 0.3 0.5 1.0 µsSync Threshold 1.2 2.0 2.8 1.2 2.0 2.8 VSync Input Current Sync Voltage = 3.5V 1.0 2.5 1.0 2.5 mAError Amplifier Section (VCM = 5.1V)Input Offset Voltage 0.5 5 2 10 mVInput Bias Current 1 10 1 10 µAInput Offset Current 1 1 µADC Open Loop Gain RL ≥≥ 10MΩΩ 60 75 60 75 dBGain-Bandwidth Product (Note 5)AV = 0dB, TJ = 25°C 12 12 MHzDC Transconductance (Notes 5 & 7)TJ = 25°°C, 30kΩΩ ≤≤ RL ≤≤ …
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