UC3844B, UC3845B, UC2844B, UC2845B
ELECTRICAL CHARACTERISTICS
(V
CC
= 15 V [Note 4], R
T
= 10 k, C
T
= 3.3 nF. For typical values T
A
= 25°C, for min/max values
T
A
is the operating ambient temperature range that applies [Note 5], unless otherwise noted.)
UC284XB
Characteristic
ERROR AMPLIFIER SECTION
Voltage Feedback Input (V
O
= 2.5 V)
Input Bias Current (V
FB
= 5.0 V)
Open Loop Voltage Gain (V
O
= 2.0 V to 4.0 V)
Unity Gain Bandwidth (T
J
= 25°C)
Power Supply Rejection Ratio (V
CC
= 12 V to 25 V)
Output Current
Sink (V
O
= 1.1 V, V
FB
= 2.7 V)
Source (V
O
= 5.0 V, V
FB
= 2.3 V)
Output Voltage Swing
High State (R
L
= 15 k to ground, V
FB
= 2.3 V)
Low State (R
L
= 15 k to V
ref
, V
FB
= 2.7 V)
(UC284XB, UC384XB)
(UC384XBV)
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 6 & 7)
(UC284XB, UC384XB)
(UC384XBV)
Maximum Current Sense Input Threshold (Note 6)
(UC284XB, UC384XB)
(UC384XBV)
Power Supply Rejection Ratio
(V
CC
= 12 V to 25 V) (Note 6)
Input Bias Current
Propagation Delay (Current Sense Input to Output)
OUTPUT SECTION
Output Voltage
Low State (I
Sink
= 20 mA)
(I
Sink
= 200 mA, UC284XB, UC384XB)
(I
Sink
= 200 mA, UC384XBV)
High State (I
Source
= 20 mA, UC284XB, UC384XB)
(I
Source
= 20 mA, UC384XBV)
(I
Source
= 200 mA)
Output Voltage with UVLO Activated (V
CC
= 6.0 V, I
Sink
= 1.0 mA)
Output Voltage Rise Time (C
L
= 1.0 nF, T
J
= 25°C)
Output Voltage Fall Time (C
L
= 1.0 nF, T
J
= 25°C)
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold
UCX844B, BV
UCX845B, BV
Minimum Operating Voltage After Turn−On
UCX844B, BV
UCX845B, BV
V
th
15
7.8
V
CC(min)
9.0
7.0
10
7.6
11
8.2
8.5
7.0
10
7.6
11.5
8.2
16
8.4
17
9.0
14.5
7.8
16
8.4
17.5
9.0
V
V
V
V
OL
−
−
−
13
−
12
−
−
−
0.1
1.6
−
13.5
−
13.4
0.1
50
50
0.4
2.2
−
−
−
−
1.1
150
150
−
−
−
13
12.9
12
−
−
−
0.1
1.6
1.6
13.5
−
13.4
0.1
50
50
0.4
2.2
2.3
−
−
−
1.1
150
150
V
ns
ns
A
V
2.85
−
V
th
0.9
−
PSRR
I
IB
t
PLH(In/Out)
−
−
−
1.0
−
70
− 2.0
150
1.1
−
−
−10
300
0.9
0.85
−
−
−
1.0
1.0
70
− 2.0
150
1.1
1.1
−
−10
300
dB
mA
ns
3.0
−
3.15
−
2.85
2.85
3.0
3.0
3.15
3.25
V
V/V
V
FB
I
IB
A
VOL
BW
PSRR
I
Sink
I
Source
V
OH
V
OL
2.45
−
65
0.7
60
2.0
− 0.5
5.0
−
−
2.5
− 0.1
90
1.0
70
12
−1.0
6.2
0.8
−
2.55
−1.0
−
−
−
−
−
−
1.1
−
2.42
−
65
0.7
60
2.0
− 0.5
5.0
−
−
2.5
− 0.1
90
1.0
70
12
−1.0
6.2
0.8
0.8
2.58
− 2.0
−
−
−
−
−
V
−
1.1
1.2
V
mA
dB
MHz
dB
mA
Symbol
Min
Typ
Max
UC384XB, XBV
Min
Typ
Max
Unit
V
OH
V
OL(UVLO)
t
r
t
f
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
high
= + 70°C for UC3844B, UC3845B
T
low
= 0°C for UC3844B, UC3845B
= − 25°C for UC2844B, UC2845B
= + 85°C for UC2844B, UC2845B
= − 40°C for UC3844BV, UC3845BV
= +105°C for UC3844BV, UC3845BV
6. This parameter is measured at the latch trip point with V
FB
= 0 V.
7. Comparator gain is defined as: A
V
=
DV
Output/Compensation
DV
Current Sense Input
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