UC3845BD Просмотр технического описания (PDF) - ON Semiconductor

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Компоненты Описание

производитель

UC3845BD

High Performance Current Mode Controllers

ON Semiconductor 

UC3844B, UC3845B, UC2844B, UC2845B

1.0nF

8(14)

10k

4(7)

2(3)

1(1)

UC3845B

7(12)

34V

Reference

2.5V R

R

Regulator

Internal

Bias

3.6V

+

−

Vref

UVLO

VCC

UVLO

+

−

Osc

+

T

0.5mA 2R

Error

Amplifier

R 1.0V

S

Q

R PWM

Latch

Current Sense

Comparator

5(9)

Vin = 15V

+

47

7(11)

1N5819

Output Load Regulation

(Open Loop Configuration)

IO (mA)

VO (V)

0

29.9

2

28.8

9

28.3

18

27.4

36

24.4

15 10

6(10)

1N5819

+

Connect to

5(8)

Pin 2 for

VO ≈ 2 (Vin)

+

47

R2

closed loop

operation.

3(5)

R1

ǒ Ǔ VO = 2.5

R2

R1

)

1

The capacitor’s equivalent series resistance must limit the Drive Output current to 1.0 A. An additional series resistor

may be required when using tantalum or other low ESR capacitors. The converter’s output can provide excellent line

and load regulation by connecting the R2/R1 resistor divider as shown.

Figure 31. Step−Up Charge Pump Converter

UC3845B

1.0nF

8(14)

10k

4(7)

2(3)

Reference

Regulator

2.5V

R

Internal

VCC

UVLO

+

−

R

Bias

3.6V

+

−

Vref

UVLO

Osc

+

T

0.5mA 2R

Error

Amplifier

R 1.0V

S

Q

R PWM

Latch

1(1)

Current Sense

Comparator

5(9)

7(12)

34V

Vin = 15V

Output Load Regulation

+

47

7(11)

IO (mA)

0

2

9

18

32

VO (V)

−14.4

−13.2

−12.5

−11.7

−10.6

15 10

6(10)

1N5819

VO ≈ −Vin

5(8)

1N5819

+ 47

3(5)

The capacitor’s equivalent series resistance must limit the Drive Output current to 1.0 A.

An additional series resistor may be required when using tantalum or other low ESR capacitors.

Figure 32. Voltage−Inverting Charge Pump Converter

http://onsemi.com

14

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