Details

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BUY UC3805N https://www.utsource.net/itm/p/483020.html

Parameter	Symbol	Min	Typical	Max	Unit	Conditions
Supply Voltage	Vcc	14	15	16	V
Operating Temperature	Toper	-40		85	°C
Storage Temperature	Tstg	-65		150	°C
Output Current (Source)	Iout	100	200	300	μA	Vcc = 15V
Output Current (Sink)	Iout	100	200	300	μA	Vcc = 15V
Frequency Range	fsw	100	500	1000	kHz
Duty Cycle	D	0.1	0.5	0.9
Reference Voltage	Vref	4.9	5.0	5.1	V
Error Amplifier Gain	Aea	100	200	300	V/V	Vcc = 15V, f = 1kHz
Error Amplifier Bandwidth	f3dB	1	10	100	kHz
Soft-Start Time	tss	100	200	300	μs	External capacitor, C = 0.1μF
Shutdown Current	Ishd	0.1	0.5	1	μA	Vcc = 15V, shutdown mode

Instructions for Using the UC3805N

1. Power Supply Connection:

   • Connect the supply voltage (Vcc) to pin 8.
   • Ground (GND) is connected to pin 4.

2. Output Configuration:

   • The output stage can be configured as either a totem-pole or open-collector configuration.
   • For totem-pole configuration, connect the output (pin 7) directly to the load.
   • For open-collector configuration, connect an external pull-up resistor from the output (pin 7) to Vcc.

3. Frequency Setting:

   • Set the switching frequency using an external resistor (Rt) and capacitor (Ct) connected between pins 6 and 7.
   • Use the formula ( f_ = frac{1.1}{R_t cdot C_t} ).

4. Duty Cycle Control:

   • Adjust the duty cycle by connecting a voltage divider network to the control input (pin 5).
   • The duty cycle can be varied from 0.1 to 0.9 by changing the voltage at this pin.

5. Reference Voltage:

   • The internal reference voltage (Vref) is available at pin 3.
   • Use this pin for setting the feedback voltage in the error amplifier.

6. Error Amplifier:

   • Connect the inverting input (pin 1) to the feedback network.
   • Connect the non-inverting input (pin 2) to the reference voltage (Vref).
   • The error amplifier gain and bandwidth can be adjusted using external components.

7. Soft-Start:

   • Implement soft-start by connecting an external capacitor (Css) to pin 6.
   • The soft-start time can be calculated using ( t_ = R_ cdot C_ ), where Rss is the internal resistor.

8. Shutdown:

   • To shut down the device, pull the shutdown pin (pin 1) low.
   • The shutdown current is very low, making it suitable for low-power applications.

9. Thermal Considerations:

   • Ensure adequate heat dissipation if operating at high temperatures or under high load conditions.
   • Use a heatsink if necessary.

10. Storage and Handling:

    • Store the device in a dry, cool place.
    • Handle with care to avoid static damage. Use ESD protection when handling the device.

(For reference only)