UC3844B, UC3845B, UC2844B, UC2845B
ELECTRICAL CHARACTERISTICS (V = 15 V [Note 7], R = 10 k, C = 3.3 nF. For typical values T = 25°C, for min/max values
CC
T
T
A
T is the operating ambient temperature range that applies [Note 8], unless otherwise noted.)
A
UC284xB
UC384xB, xBV,
NCV384xBV
Characteristic
Symbol
Min
Typ
Max
Min
Typ
Max
Unit
OSCILLATOR SECTION
Discharge Current (V
= 2.0 V)
T = 25°C
(UC284XB, UC384XB)
(UC384XBV)
I
dischg
7.8
7.5
−
8.3
−
−
8.8
8.8
−
7.8
7.6
7.2
8.3
−
−
8.8
8.8
8.8
mA
OSC
J
T = T to T
A
low
high
ERROR AMPLIFIER SECTION
Voltage Feedback Input (V = 2.5 V)
V
2.45
−
2.5
− 0.1
90
2.55
−1.0
−
2.42
−
2.5
− 0.1
90
2.58
− 2.0
−
V
mA
O
FB
Input Bias Current (V = 5.0 V)
I
IB
FB
Open Loop Voltage Gain (V = 2.0 V to 4.0 V)
A
VOL
65
65
dB
O
Unity Gain Bandwidth (T = 25°C)
BW
0.7
60
1.0
70
−
0.7
60
1.0
70
−
MHz
dB
J
Power Supply Rejection Ratio (V = 12 V to 25 V)
PSRR
−
−
CC
Output Current − Sink (V = 1.1 V, V = 2.7 V)
I
Sink
2.0
− 0.5
12
−1.0
−
−
2.0
− 0.5
12
−1.0
−
−
mA
O
FB
Output Current − Source (V = 5.0 V, V = 2.3 V)
I
O
FB
Source
Output Voltage Swing
High State (R = 15 k to ground, V = 2.3 V)
V
V
OH
5.0
6.2
−
5.0
6.2
−
L
FB
Low State (R = 15 k to V , V = 2.7 V)
V
OL
L
ref FB
(UC284XB, UC384XB)
(UC384XBV)
−
−
0.8
−
1.1
−
−
−
0.8
0.8
1.1
1.2
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 9 & 10)
(UC284XB, UC384XB)
A
V/V
V
V
2.85
−
3.0
−
3.15
−
2.85
2.85
3.0
3.0
3.15
3.25
(UC384XBV)
Maximum Current Sense Input Threshold (Note 9)
(UC284XB, UC384XB)
V
th
0.9
−
1.0
−
1.1
−
0.9
0.85
1.0
1.0
1.1
1.1
(UC384XBV)
Power Supply Rejection Ratio (V = 12 V to 25 V) (Note 9)
PSRR
−
−
−
70
−
−
−
−
70
−
dB
mA
ns
CC
Input Bias Current
I
− 2.0
150
−10
300
− 2.0
150
−10
300
IB
PLH(In/Out)
Propagation Delay (Current Sense Input to Output)
t
OUTPUT SECTION
Output Voltage
V
Low State (I
= 20 mA)
= 200 mA, UC284XB, UC384XB)
= 200 mA, UC384XBV)
= 20 mA, UC284XB, UC384XB)
= 20 mA, UC384XBV)
= 200 mA)
V
−
−
−
13
−
12
0.1
1.6
−
13.5
−
0.4
2.2
−
−
−
−
−
−
13
12.9
12
0.1
1.6
1.6
13.5
−
0.4
2.2
2.3
−
−
−
Sink
OL
(I
Sink
(I
Sink
High State(I
V
OH
Source
Source
Source
(I
(I
13.4
−
13.4
Output Voltage with UVLO Activated (V = 6.0 V, I
= 1.0 mA)
V
−
−
−
0.1
50
50
1.1
150
150
−
−
−
0.1
50
50
1.1
150
150
V
CC
Sink
OL(UVLO)
Output Voltage Rise Time (C = 1.0 nF, T = 25°C)
t
r
ns
ns
L
J
Output Voltage Fall Time (C = 1.0 nF, T = 25°C)
t
f
L
J
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold
UCX844B, BV
UCX845B, BV
V
15
7.8
16
8.4
17
9.0
14.5
7.8
16
8.4
17.5
9.0
V
V
th
Minimum Operating Voltage After Turn−On
UCX844B, BV
UCX845B, BV
V
9.0
7.0
10
7.6
11
8.2
8.5
7.0
10
7.6
11.5
8.2
CC(min)
7. Adjust V above the Startup threshold before setting to 15 V.
CC
8. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
T
= 0°C for UC3844B, UC3845B
T
= + 70°C for UC3844B, UC3845B
= + 85°C for UC2844B, UC2845B
= +105°C for UC3844BV, UC3845BV
= +125°C for NCV384xBV
low
high
= − 25°C for UC2844B, UC2845B
= − 40°C for UC384xBV, NCV384xBV
9. This parameter is measured at the latch trip point with V = 0 V.
10.Comparator gain is defined as: A =
FB
DV Output/Compensation
DV Current Sense Input
V
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