UC184xA/284xA/384xA

PRODUCT DA T ABOOK 1996/1997

Copyright © 1995

Rev. 1.2a 10/25

4

ELECTRICAL CHARACTERISTICS

(Con't.)

Under-Voltage Lockout Section

Parameter

Symbol

Test Conditions

Start Threshold

x842A/4A

x843A/5A

Min. Operation Voltage After Turn-On

x842A/4A

x843A/5A

UC384xA

Units

Min. Typ. Max. Min. Typ. Max.

UC184xA/284xA

15

16

17

14.5

16

17.5

V

7.8

8.4

9.0

7.8

8.4

9.0

V

9

10

11

8.5

10

11.5

V

7.0

7.6

8.2

7.0

7.6

8.2

V

PWM Section

Maximum Duty Cycle

x842A/3A

x844A/5A

Minimum Duty Cycle

94

96

100

94

96

100

%

47

48

50

47

48

50

%

00

%

Total Standby Section

Start-Up Current

Operating Supply Current

I

CC

Zener Voltage

V

Z

I

0.3

0.5

0.3

0.5

mA

11

17

11

17

mA

30

35

30

35

V

BLOCK DIAGRAM

** - POWER GROUND and GROUND are internally connected for 8 pin packages.

*** - Toggle flip flop used only in x844A and x845A series.

Notes: 2. These parameters, although guaranteed, are not 100% tested in

production.

3. Parameter measured at trip point of latch with V

VFB

= 0.

4. Gain defined as: A

; 0

≤ V

5. Adjust V

6. Output frequency equals oscillator frequency for the UC1842A

and UC1843A. Output frequency is one half oscillator frequency

for the UC1844A and UC1845A.

7. "Temperature stability, sometimes referred to as average temperature

coefficient, is described by the equation:

Temp Stability =

V

voltage measured over the appropriate temperature range. Note that

the extremes in voltage do not necessarily occur at the extremes in

temperature."

V

REF

(max.) - V

REF

(min.)

T

J

(max.) - T

J

(min.)

∆ V

COMP

∆ V

ISENSE

UVLO

S / R

5V

Ref

Internal

Bias

34V

Error Amp

1V

Current Sense

Comparator

PWM

Latch

S

R

R

Oscillator

2R

**

T

***

V

REF

Good Logic

2.5V

UVLO

16V (1842A/4A)

8.4V (1843A/5A)

Hysteresis

6V (1842A/4A)

0.8V (1843A/5A)

COMP

CURRENT SENSE

V

FB

R

GROUND

*

V

CC

V

REF

5.0V

50mA

V

C

*

OUTPUT

POWER GROUND**