UC1842A-EP, UC1843A-EP, UC1844A-EP, UC1845A-EP

CURRENT-MODE PWM CONTROLLER

SGLS134B – SEPTEMBER 2002 – REVISED APRIL 2003

5

POST OFFICE BOX 655303

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

PWM Section

Maximum duty cycle

UC1842A, UC1843A

94

96

100

%

Maximum duty cycle

UC1844A, UC1845A

47

48

50

%

Minimum duty cycle

0

%

Total Standby Current

Start-up current

0.3

0.5

mA

Operating supply current

FB = 0 V,

SENSE = 0 V

11

17

mA

VCC internal zener voltage

ICC = 25 mA

30

34

V

NOTES:

1. Adjust VCC above the start threshold before setting at 15 V.

2. Not production tested.

3. Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:

Temp Stability =

VREF (max) – VREF (min)

TJ (max) – TJ (min)

. VREF (max) and VREF (min) are the maximum and minimum reference voltage

measured over the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at the extremes in

temperature.

4. Output frequency equals oscillator frequency for the UC1842A and UC1843A. Output frequency is one half oscillator frequency for

the UC1844A and UC1845A.

5. This parameter is measured with RT = 10 kΩ to VREF. This contributes approximately 300 µA of current to the measurement. The

total current flowing into the RT/C pin will be approximately 300 µA higher than the measured value.

6. Parameter measured at trip point of latch with VFB at 0 V.

7. Gain is defined by:

A =

DVCOMP

DVSENSE

; 0

v VSENSE v 0.8 V.

PARAMETER MEASUREMENT INFORMATION

Error Amp can source and sink up to 0.5 mA, and sink up to 2 mA.

Figure 1. Error Amp Configuration