Details

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BUY UC3843AL https://www.utsource.net/itm/p/1552969.html
TVS BI-DIRECTIONAL 36V 600W SMB

Parameter	Symbol	Min	Typical	Max	Unit
Supply Voltage	Vcc	8.0	-	40.0	V
Operating Current	ICC	-	1.5	-	mA
Start-Up Current	ISTR	-	1.0	-	mA
Reference Voltage	Vref	2.500	-	2.575	V
Error Amplifier Transconductance	GM	-	6.0	-	mA/V
Oscillator Frequency Range	fOSC	1.0	-	500.0	kHz
Slope Compensation Current	ISLOPE	-	0.2	-	μA
Maximum Duty Cycle	DMAX	-	95%	-	%
Shutdown Pin Threshold	VSHDN	1.0	-	1.4	V
Soft-Start Capacitance	CSS	-	1.0	-	nF
Maximum Output Current	IOUT	-	1.0	-	A
Operating Temperature	Toper	-40	-	125	°C
Storage Temperature	Tstg	-65	-	150	°C

Instructions for Using UC3843AL

1. Power Supply (Vcc):

   • Ensure the supply voltage is within the range of 8.0V to 40.0V.
   • Use a bypass capacitor (typically 0.1μF) between Vcc and ground to filter out noise.

2. Start-Up Circuit:

   • The IC starts up when the voltage on the Vcc pin exceeds the start-up threshold.
   • The start-up current is typically 1.0mA, so ensure the power supply can handle this initial surge.

3. Reference Voltage (Vref):

   • The internal reference voltage is nominally 2.5V and is used as a stable reference for the error amplifier.

4. Error Amplifier:

   • Connect the feedback signal to the inverting input of the error amplifier.
   • The non-inverting input is connected to the reference voltage (Vref).

5. Oscillator:

   • Set the oscillator frequency using an external resistor (RT) and capacitor (CT).
   • The formula for calculating the frequency is ( f_ = frac{1.1}{R_T cdot C_T} ).

6. Slope Compensation:

   • For high duty cycle applications, use slope compensation to prevent subharmonic oscillation.
   • The slope compensation current is typically 0.2μA.

7. Maximum Duty Cycle:

   • The maximum duty cycle is 95%. Ensure the control loop is designed to avoid exceeding this limit.

8. Shutdown Pin:

   • The shutdown pin can be used to disable the IC by pulling it low (below 1.0V).
   • To enable the IC, keep the shutdown pin above 1.4V.

9. Soft-Start:

   • Connect a capacitor to the soft-start pin to gradually increase the output voltage during startup.
   • A typical value for the soft-start capacitor is 1.0nF.

10. Output Stage:

    • The output stage is capable of driving an external MOSFET or other power devices.
    • Ensure the load does not exceed the maximum output current of 1.0A.

11. Thermal Considerations:

    • The operating temperature range is from -40°C to 125°C.
    • The storage temperature range is from -65°C to 150°C.
    • Use proper heat sinking if the IC is expected to dissipate significant power.

12. Layout Guidelines:

    • Keep the layout compact to minimize parasitic inductances and capacitances.
    • Place decoupling capacitors close to the IC to reduce noise and improve stability.

By following these instructions, you can ensure reliable operation of the UC3843AL in your power supply design.

(For reference only)