UC3842A, UC3843A, UC2842A, UC2843A
http://onsemi.com
4
ELECTRICAL CHARACTERISTICS (V
CC
= 15 V, [Note 4], R
T
= 10 k, C
T
= 3.3 nF, T
A
= T
low
to T
high
[Note 5],
unless otherwise noted.)
UC284XA UC384XA
Characteristics Symbol Min Typ Max Min Typ Max Unit
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 6 & 7) A
V
2.85 3.0 3.15 2.85 3.0 3.15 V/V
Maximum Current Sense Input Threshold (Note 6) V
th
0.9 1.0 1.1 0.9 1.0 1.1 V
Power Supply Rejection Ratio
V
CC
= 12 to 25 V (Note 6)
PSRR
− 70 − − 70 −
dB
Input Bias Current I
IB
− −2.0 −10 − −2.0 −10
A
Propagation Delay (Current Sense Input to Output) t
PLH(in/out)
− 150 300 − 150 300 ns
OUTPUT SECTION
Output Voltage
Low State (I
Sink
= 20 mA)
Low State (I
Sink
= 200 mA)
High State (I
Sink
= 20 mA)
High State (I
Sink
= 200 mA)
V
OL
V
OH
−
−
13
12
0.1
1.6
13.5
13.4
0.4
2.2
−
−
−
−
13
12
0.1
1.6
13.5
13.4
0.4
2.2
−
−
V
Output Voltage with UVLO Activated
V
CC
= 6.0 V, I
Sink
= 1.0 mA
V
OL(UVLO)
− 0.1 1.1 − 0.1 1.1
V
Output Voltage Rise Time (C
L
= 1.0 nF, T
J
= 25°C) t
r
− 50 150 − 50 150 ns
Output Voltage Fall Time (C
L
= 1.0 nF, T
J
= 25°C) t
f
− 50 150 − 50 150 ns
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold
UCX842A
UCX843A
V
th
15
7.8
16
8.4
17
9.0
14.5
7.8
16
8.4
17.5
9.0
V
Minimum Operating Voltage After Turn−On
UCX842A
UCX843A
V
CC(min)
9.0
7.0
10
7.6
11
8.2
8.5
7.0
10
7.6
11.5
8.2
V
PWM SECTION
Duty Cycle
Maximum
Minimum
DC
max
DC
min
94
−
96
−
−
0
94
−
96
−
−
0
%
TOTAL DEVICE
Power Supply Current (Note 4)
Startup:
(V
CC
= 6.5 V for UCX843A,
(V
CC
= 14 V for UCX842A) Operating
I
CC
−
−
0.5
12
1.0
17
−
−
0.5
12
1.0
17
mA
Power Supply Zener Voltage (I
CC
= 25 mA) V
Z
30 36 − 30 36 − V
4. Adjust V
CC
above the Startup threshold before setting to 15 V.
5. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
T
low
=0°C for UC3842A, UC3843A T
high
= +70°C for UC3842A, UC3843A
−25°C for UC2842A, UC2843A +85°C for UC2842A, UC2843A
6. This parameter is measured at the latch trip point with V
FB
= 0 V.
7. Comparator gain is defined as: A
V
V Output Compensation
V Current Sense Input
