UC3844, 45 UC2844, 45
ELECTRICAL CHARACTERISTICS
(VCC = 15 V, [Note 2], RT = 10 k, CT = 3.3 nF, TA = Tlow to Thigh [Note 3],
unless otherwise noted,)
UC284X
Characteristics
ERROR AMPLIFIER SECTION
Voltage Feedback Input (VO = 2.5 V)
Input Bias Current (VFB = 2.7 V)
Open Loop Voltage Gain (VO = 2.0 V to 4.0 V)
Unity Gain Bandwidth (TJ = 25°C)
Power Supply Rejection Ratio (VCC = 12 V to 25 V)
Output Current
Sink (VO = 1.1 V, VFB = 2.7 V)
Source (VO = 5.0 V, VFB = 2.3 V)
Output Voltage Swing
High State (RL = 15 k to ground, VFB = 2.3 V)
Low State (RL = 15 k to Vref, VFB = 2.7 V)
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 4 & 5)
Maximum Current Sense Input Threshold (Note 4)
Power Supply Rejection Ratio
VCC = 12 V to 25 V (Note 4)
Input Bias Current
Propagation Delay (Current Sense Input to Output)
OUTPUT SECTION
Output Voltage
Low State (ISink = 20 mA)
(ISink = 200 mA)
High State (ISink = 20 mA)
(ISink = 200 mA)
Output Voltage with UVLO Activated
VCC = 6.0 V, ISink = 1.0 mA
Output Voltage Rise Time (CL = 1.0 nF, TJ = 25°C)
Output Voltage Fall Time (CL = 1.0 nF, TJ = 25°C)
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold
UCX844
UCX845
Minimum Operating Voltage After Turn–On
UCX844
UCX845
PWM SECTION
Duty Cycle
Maximum
Minimum
TOTAL DEVICE
Power Supply Current (Note 2)
Startup:
(VCC = 6.5 V for UCX845A,
(VCC
14 V for UCX844) Operating
Power Supply Zener Voltage (ICC = 25 mA)
ICC
–
–
VZ
30
0.5
12
36
1.0
17
–
–
–
30
0.5
12
36
1.0
17
–
V
mA
%
DCmax
DCmin
46
–
48
–
50
0
47
–
48
–
50
0
Vth
15
7.8
VCC(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
VOL
VOH
VOL(UVLO)
–
tr
tf
–
–
0.1
50
50
1.1
150
150
–
–
–
0.1
50
50
1.1
150
150
ns
ns
–
–
12
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
AV
Vth
PSRR
–
IIB
tPLH(IN/OUT)
–
–
70
–2.0
150
–
–10
300
–
–
–
70
–2.0
150
–
–10
300
µA
ns
2.85
0.9
3.0
1.0
3.15
1.1
2.85
0.9
3.0
1.0
3.15
1.1
V/V
V
dB
VFB
IIB
AVOL
BW
PSRR
ISink
ISource
VOH
VOL
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
2.58
–2.0
–
–
–
–
–
V
–
1.1
V
µA
dB
MHz
dB
mA
Symbol
Min
Typ
Max
Min
UC384X
Typ
Max
Unit
NOTES:
2. Adjust VCC above the Startup threshold before setting to 15 V.
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible
Tlow =
–20°C
for UC3844, UC3845
Thigh = +70°C for UC3844, UC3845
Tlow =
–25°C for UC2844, UC2845
Thigh =
+85°C for UC2844, UC2845
4. This parameter is measured at the latch trip point with VFB = 0 V.
∆V
Output Compensation
5. Comparator gain is defined as: AV
∆V
Current Sense Input
MOTOROLA ANALOG IC DEVICE DATA
3
ONSEMI [ ON SEMICONDUCTOR ]
