UC3844

UC3844

Category: IC Chips

Specifications
SKU
12536147
Details

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Parameter Symbol Min Typ Max Unit Description
Supply Voltage Vcc 10.0 16.0 35.0 V Operating range of the supply voltage
Start-Up Current ISTART - 2.0 - mA Current required to start the IC
Operating Current IOP 2.5 3.5 4.5 mA Current required for normal operation
Shutdown Current ISD 50 75 100 μA Current consumption in shutdown mode
Oscillator Frequency fOSC 100 500 1000 kHz Range of the oscillator frequency
Reference Voltage VREF 4.95 5.0 5.05 V Stable reference voltage output
Error Amplifier Gain AEA 50 100 150 V/μA Gain of the error amplifier
Compensation Pin Output Current ICO 0.1 0.5 1.0 mA Maximum current from the compensation pin
PWM Comparator Input Voltage VCOMP 0.5 1.0 1.5 V Input voltage range for the PWM comparator
PWM Output Duty Cycle D 0 50 100 % Range of the PWM output duty cycle
Thermal Shutdown Temperature TSD 150 160 170 °C Temperature at which the IC shuts down to prevent damage

Instructions for Using the UC3844

  1. Supply Voltage (Vcc):

    • Ensure the supply voltage is within the specified range (10V to 35V) to avoid damage or improper operation.
  2. Start-Up Current (ISTART):

    • The IC requires a minimum start-up current of 2mA. Ensure the power supply can provide this current.
  3. Operating Current (IOP):

    • The operating current is typically 3.5mA. Design the power supply to handle this current continuously.
  4. Shutdown Current (ISD):

    • In shutdown mode, the IC consumes approximately 75μA. This is useful for low-power applications.
  5. Oscillator Frequency (fOSC):

    • Set the oscillator frequency using an external resistor and capacitor. The typical range is 100kHz to 1000kHz.
  6. Reference Voltage (VREF):

    • The stable reference voltage is 5.0V ± 1%. Use this for precise voltage regulation.
  7. Error Amplifier Gain (AEA):

    • The error amplifier gain is typically 100 V/μA. Adjust the feedback network to achieve the desired regulation.
  8. Compensation Pin Output Current (ICO):

    • The maximum current from the compensation pin is 1.0mA. Use this for loop compensation to stabilize the control loop.
  9. PWM Comparator Input Voltage (VCOMP):

    • The PWM comparator input voltage should be within 0.5V to 1.5V. This voltage determines the PWM duty cycle.
  10. PWM Output Duty Cycle (D):

    • The PWM output duty cycle can range from 0% to 100%. Use the feedback and control circuitry to set the desired duty cycle.
  11. Thermal Shutdown Temperature (TSD):

    • The IC will shut down if the temperature exceeds 160°C to prevent thermal damage. Ensure proper heat dissipation.

Additional Notes:

  • Always refer to the datasheet for detailed information and specific application notes.
  • Proper PCB layout and component selection are crucial for reliable operation.
  • Use appropriate decoupling capacitors near the Vcc pin to ensure stable operation.
(For reference only)

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