UC2845 datasheet(8/11 Pages) STMICROELECTRONICS

Part #	UC2845

Description	CURRENTMODE PWM CONTROLLER

PDF	11 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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8 / 11 page

Figure 11 : Off-line Flyback Regulator.

Power Supply Specifications

1. Input Voltage :

95 VAC to 130 VAC

(50 Hz/60 Hz)

2. Line Isolation :

3750 V

3. Switching Frequency :

40 KHz

4. Efficiency @ Full Load : 70 %

5. Output Voltage :

A. + 5 V,

± 5 % : 1 A to 4 A load

Ripple voltage : 50 mV P-P Max.

B. + 12 V,

± 3 % : 0.1 A to 0.3 A load

Ripple voltage : 100 mV P-P Max.

C. – 12 V,

± 3 % : 0.1 A to 0.3 A load

Ripple voltage : 100 mV P-P Max.

Figure 12 : Slope Compensation.

A fraction of the oscillator ramp can be resistively

summed with the current sense signal to provide

slope compensation for converters requiring duty

cycles over 50 %.

Note that capacitor, C, forms a filter with R2 to su-

press the leading edge switch spikes.

UC2842/3/4/5-UC3842/3/4/5

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UC2845 Datasheet(PDF) 8 Page - STMicroelectronics