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UC1842A/3A/4A/5A
UC2842A/3A/4A/5A
UC3842A/3A/4A/5A
Current Mode PWM Controller
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
Optimized for Off-line and DC to DC
Converters
Low Start Up Current (<0.5mA)
Trimmed Oscillator Discharge Current
Automatic Feed Forward Compensation
Pulse-by-Pulse Current Limiting
Enhanced Load Response Characteristics
Under-Voltage Lockout With Hysteresis
Double Pulse Suppression
Part #
UVLO On
16.0V
8.5V
16.0V
8.5V
UVLO Off
10.0V
7.9V
10.0V
7.9V
Maximum Duty
Cycle
<100%
<100%
<50%
<50%
DESCRIPTION
The UC1842A/3A/4A/5A family of control ICs is a pin for pin compati-
ble improved version of the UC3842/3/4/5 family. Providing the nec-
essary features to control current mode switched mode power
supplies, this family has the following improved features. Start up cur-
rent is guaranteed to be less than 0.5mA. Oscillator discharge is
trimmed to 8.3mA. During under voltage lockout, the output stage
can sink at least 10mA at less than 1.2V for V
CC
over 5V.
The difference between members of this family are shown in the table
below.
High Current Totem Pole Output
UC1842A
Internally Trimmed Bandgap Reference
500kHz Operation
Low R
O
Error Amp
UC1843A
UC1844A
UC1845A
BLOCK DIAGRAM
Note 1: A/B A = DIL-8 Pin Number. B = SO-14 Pin Number.
Note 2: Toggle flip flop used only in 1844A and 1845A.
SLUS224A - SEPTEMBER 1994 - REVISED APRIL 2002
CONNECTION DIAGRAMS
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (Low Impedance Source) . . . . . . . . . . . . . . 30V
Supply Voltage (I
CC
mA) . . . . . . . . . . . . . . . . . . . . Self Limiting
Output Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
±
1A
Output Energy (Capacitive Load). . . . . . . . . . . . . . . . . . . . . 5µJ
Analog Inputs (Pins 2, 3). . . . . . . . . . . . . . . . . . . -0.3V to +6.3V
Error Amp Output Sink Current . . . . . . . . . . . . . . . . . . . . 10mA
Power Dissipation at T
A
≤
25°C (DIL-8) . . . . . . . . . . . . . . . . 1W
Storage Temperature Range . . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . 300°C
Note 1. All voltages are with respect to Ground, Pin 5. Currents
are positive into, negative out of the specified terminal. Consult
Packaging Section of Databook for thermal limitations and con-
siderations of packages. Pin numbers refer to DIL package only.
UC1842A/3A/4A/5A
UC2842A/3A/4A/5A
UC3842A/3A/4A/5A
PLCC-20, LCC-20
(TOP VIEW)
Q, L Packages
PACKAGE PIN FUNCTION
FUNCTION
PIN
N/C
1
Comp
2
N/C
3-4
V
FB
5
N/C
6
I
SENSE
7
N/C
8-9
R
T
/C
T
10
N/C
11
Pwr Gnd
12
Gnd
13
N/C
14
Output
15
N/C
16
V
C
17
V
CC
18
N/C
19
V
REF
20
SOIC-14 (TOP VIEW)
D Package
DIL-8, SOIC-8 (TOP VIEW)
J or N, D8 Package
SOIC-WIDE16 (TOP VIEW)
DW Package
N/C
N/C
COMP
VFB
ISENSE
RT/CT
N/C
N/C
1
2
3
4
5
6
7
8
16 N/C
15 VREF
14 VCC
13 VCC
12 OUTPUT
11 GND
10 PWRGND
9 N/C
2
UC1842A/3A/4A/5A
UC2842A/3A/4A/5A
UC3842A/3A/4A/5A
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for –55°C
≤
T
A
≤
125°C for the
UC184xA; –40°C
≤
T
A
≤
125°C for the UC284xAQ; –40°C
≤
T
A
≤
85°C for the UC284xA; 0
≤
T
A
≤
70°C for the UC384xA; V
CC
= 15V
(Note 5); R
T
= 10k; C
T
= 3.3nF; T
A
= T
J
; Pin numbers refer to DIL-8.
PARAMETER
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temp. Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Initial Accuracy
Voltage Stability
Temp. Stability
Amplitude
Discharge Current
Error Amp Section
Input Voltage
Input Bias Current
A
VOL
Unity Gain Bandwidth
PSRR
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
Current Sense Section
Gain
Maximum Input Signal
PSRR
Input Bias Current
Delay to Output
Output Section
Output Low Level
Output High Level
Rise Time
Fall Time
UVLO Saturation
TEST CONDITIONS
UC184xA\UC284xA
MIN. TYP. MAX.
4.95
5.00
6
6
0.2
5.05
20
25
0.4
5.1
UC384xA
UNITS
MIN. TYP. MAX.
4.90
5.00
6
6
0.2
5.10
20
25
0.4
5.18
V
mV
mV
mV/°C
V
µV
mV
mA
kHz
%
%
V
mA
mA
V
µA
dB
MHz
dB
mA
mA
V
V
V/V
V
dB
µA
ns
V
V
V
V
ns
ns
V
T
J
= 25°C, I
O
= 1mA
12
≤
V
IN 25V
1
≤
I
O
≤
20mA
(Note 2, Note 7)
Line, Load, Temp.
10Hz
≤
f
≤
10kHz
T
J
= 25°C (Note 2)
T
A
= 125°C, 1000Hrs. (Note 2)
4.9
50
5
-100
52
0.2
5
1.7
8.3
4.82
50
5
-100
52
0.2
5
1.7
8.3
-30
T
J
= 25°C (Note 6)
12
≤
V
CC
≤
25V
T
MIN
≤
T
A
≤
T
MAX
(Note 2)
V
PIN 4
peak to peak (Note 2)
T
J
= 25°C, V
PIN 4
= 2V (Note 8)
V
PIN 4
= 2V (Note 8)
V
PIN 1
= 2.5V
2
≤
V
O
≤
4V
T
J
= 25°C (Note 2)
12
≤
V
CC
≤
25V
V
PIN 2
= 2.7V, V
PIN 1
= 1.1V
V
PIN 2
= 2.3V, V
PIN 1
= 5V
V
PIN 2
= 2.3V, R
L
= 15k to ground
V
PIN 2
= 2.7V, R
L
= 15k to Pin 8
(Note 3, Note 4)
V
PIN 1
= 5V (Note 3)
12
≤
V
CC
≤
25V (Note 3)
V
PIN 3
= 0 to 2V (Note 2)
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
T
J
= 25°C, C
L
= 1nF (Note 2)
T
J
= 25°C, C
L
= 1nF (Note 2)
V
CC
= 5V, I
SINK
= 10mA
47
25
-180
57
1
-30
47
25
-180
57
1
7.8
7.5
2.45
65
0.7
60
2
-0.5
5
8.8
8.8
2.55
-1
7.8
7.6
2.42
65
0.7
60
2
-0.5
5
8.8
8.8
2.58
-2
2.50
-0.3
90
1
70
6
-0.8
6
0.7
3
1
70
-2
150
0.1
15
13.5
13.5
50
50
0.7
1.1
3.15
1.1
-10
300
0.4
2.2
13
12
150
150
1.2
2.85
0.9
2.50
-0.3
90
1
70
6
-0.8
6
0.7
3
1
70
-2
150
0.1
15
13.5
13.5
50
50
0.7
1.1
3.15
1.1
-10
300
0.4
2.2
2.85
0.9
13
12
150
150
1.2
3
UC1842A/3A/4A/5A
UC2842A/3A/4A/5A
UC3842A/3A/4A/5A
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for –55°C
≤
T
A
≤
125°C for the
UC184xA; –40°C
≤
T
A
≤
125°C for the UC284xAQ; –40°C
≤
T
A
≤
85°C for the UC284xA; 0
≤
T
A
≤
70°C for the UC384xA; V
CC
= 15V
(Note 5); R
T
= 10k; C
T
= 3.3nF; T
A
= T
J
; Pin numbers refer to DIL-8.
PARAMETER
Under-Voltage Lockout Section
Start Threshold
Min. Operation Voltage After
Turn On
PWM Section
Maximum Duty Cycle
Minimum Duty Cycle
Total Standby Current
Start-Up Current
Operating Supply Current
V
CC
Zener Voltage
TEST CONDITIONS
UC184xA\UC284xA
MIN. TYP. MAX.
15
7.8
9
7.0
94
47
16
8.4
10
7.6
96
48
17
9.0
11
8.2
100
50
0
0.5
17
30
UC384xA
UNITS
MIN. TYP. MAX.
14.5
7.8
8.5
7.0
94
47
16
8.4
10
7.6
96
48
17.5
9.0
11.5
8.2
100
50
0
0.5
17
V
V
V
V
%
%
%
mA
mA
V
x842A/4A
x843A/5A
x842A/4A
x843A/5A
x842A/3A
x844A/5A
V
PIN 2
= V
PIN 3
= 0V
I
CC
= 25mA
30
0.3
11
34
0.3
11
34
Note 2:
Ensured by design, but not 100% production tested.
Note 3:
Parameter measured at trip point of latch with V
PIN2
= 0.
∆
VPIN 1
; 0 V
PIN 3
0.8V.
Note 4:
Gain defined as: A
=
∆
VPIN 3
Note 5:
Adjust V
CC
above the start threshold before setting at 15V.
Note 6:
Output frequency equals oscillator frequency for the UC1842A and UC1843A. Output frequency is one half oscillator fre-
quency for the UC1844A and UC1845A.
Note 7:
“Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:
VREF
(
max
)
−
VREF
(
min
)
.V
REF
(max) and V
REF
(min) are the maximum & minimum reference volt-
Temp Stability
=
TJ
(
max
)
−
TJ
(
min
)
age measured over the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at the extremes
in temperature.”
Note 8:
This parameter is measured with R
T
= 10k to V
REF
.This contributes approximately 300 A of current to the measurement.
The total current flowing into the R
T
/C
pin will be approximately 300
A higher than the measured value.
Error Amp Configuration
Error Amp can Source and Sink up to 0.5mA, and Sink up to 2mA.
4
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