Datasheet

UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
electrical characteristics, T
A
= –40_C to 125_C, V
CC
= 15 V (see Note 1), R
T
= 10 kΩ, C
T
= 3.3 nF, and
T
A
= T
J
(unless otherwise stated)
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
PWM Section
Maximum duty cycle
UC2842A, UC2843A 94 96 100
%
Maximum duty cycle
UC2844A, UC2845A 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
V
CC
internal zener voltage I
CC
= 25 mA 30 34 V
NOTES: 1. Adjust V
CC
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 =
V
REF
(max) – V
REF
(min)
T
J
(max) – T
J
(min)
. V
REF
(max) and V
REF
(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 UC2842A and UC2843A. Output frequency is one half oscillator frequency for the
UC2844A and UC2845A.
5. This parameter is measured with R
T
= 10 kΩ to V
REF
. This contributes approximately 300 µA of current to the measurement. The total
current flowing into the R
T/C
pin will be approximately 300 µA higher than the measured value.
6. Parameter measured at trip point of latch with V
FB
at 0 V.
7. Gain is defined by:
A =
DV
COMP
DV
SENSE
; 0 v V
SENSE
v 0.8 V.
PA
RAMETER MEASUREMENT INFORMATION
Error Amp can source and sink up to 0.5 mA, and sink up to 2 mA.
Figure 1. Error Amp Configuration