UC3842B, UC3843B,
UC2842B, UC2843B
High Performance
Current Mode Controllers
The UC3842B, UC3843B series are high performance fixed
frequency current mode controllers. They are specifically designed for
Off−Line and DC−DC converter applications offering the designer a
cost−effective solution with minimal external components. These
integrated circuits feature a trimmed oscillator for precise duty cycle
control, a temperature compensated reference, high gain error
amplifier, current sensing comparator, and a high current totem pole
output ideally suited for driving a power MOSFET.
Also included are protective features consisting of input and
reference undervoltage lockouts each with hysteresis, cycle−by−cycle
current limiting, programmable output deadtime, and a latch for single
pulse metering.
These devices are available in an 8−pin dual−in−line and surface
mount (SOIC−8) plastic package as well as the 14−pin plastic surface
mount (SOIC−14). The SOIC−14 package has separate power and
ground pins for the totem pole output stage.
The UCX842B has UVLO thresholds of 16 V (on) and 10 V (off),
ideally suited for off−line converters. The UCX843B is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).
Features
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8
1
PDIP−8
N SUFFIX
CASE 626
14
1
SOIC−14
D SUFFIX
CASE 751A
8
1
SOIC−8
D1 SUFFIX
CASE 751
•
•
•
•
•
•
•
•
•
•
Trimmed Oscillator for Precise Frequency Control
Oscillator Frequency Guaranteed at 250 kHz
Current Mode Operation to 500 kHz
Automatic Feed Forward Compensation
Latching PWM for Cycle−By−Cycle Current Limiting
Internally Trimmed Reference with Undervoltage Lockout
High Current Totem Pole Output
Undervoltage Lockout with Hysteresis
Low Startup and Operating Current
This is a Pb−Free and Halide−Free Device
V
CC
V
ref
8(14)
R
R
R
T
/C
T
4(7)
V
ref
Undervoltage
Lockout
Oscillator
Latching
PWM
+
-
PIN CONNECTIONS
Compensation
Voltage Feedback
Current Sense
R
T
/C
T
1
2
3
4
8
7
6
5
V
ref
V
CC
Output
GND
(Top View)
Compensation
NC
Voltage Feedback
NC
Current Sense
NC
R
T
/C
T
V
C
7(11)
Output
6(10)
Power
Ground
5(8)
Current
Sense
3(5) Input
1
2
3
4
5
6
7
14
13
12
11
10
9
8
7(12)
5.0V
Reference
V
CC
Undervoltage
Lockout
V
ref
NC
V
CC
V
C
Output
GND
Power Ground
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 17 of this data sheet.
Voltage
Feedback
Input
2(3)
Output
Compensation
1(1)
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 19 of this data sheet.
Error
Amplifier
GND
5(9)
Pin numbers in parenthesis are for the D suffix SOIC−14 package.
Figure 1. Simplified Block Diagram
©
Semiconductor Components Industries, LLC, 2013
September, 2013
−
Rev. 17
1
Publication Order Number:
UC3842B/D
UC3842B, UC3843B, UC2842B, UC2843B
MAXIMUM RATINGS
Rating
Bias and Driver Voltages (Zero Series Impedance, see also Total Device spec)
Total Power Supply and Zener Current
Output Current, Source or Sink
Output Energy (Capacitive Load per Cycle)
Current Sense, Voltage Feedback, V
ref
and Rt/Ct Inputs
Compensation
Output
Error Amp Output Sink Current
Power Dissipation and Thermal Characteristics
D Suffix, Plastic Package, SOIC−14 Case 751A
Maximum Power Dissipation @ T
A
= 25°C
Thermal Resistance, Junction−to−Air
D1 Suffix, Plastic Package, SOIC−8 Case 751
Maximum Power Dissipation @ T
A
= 25°C
Thermal Resistance, Junction−to−Air
N Suffix, Plastic Package, Case 626
Maximum Power Dissipation @ T
A
= 25°C
Thermal Resistance, Junction−to−Air
Operating Junction Temperature
Operating Ambient Temperature
UC3842B, UC3843B
UC2842B, UC2843B
UC2843D
UC3842BV, UC3843BV
Storage Temperature Range
Symbol
V
CC
, V
C
(I
CC
+ I
Z
)
I
O
W
V
in
V
comp
V
o
I
O
Value
30
30
1.0
5.0
−
0.3 to + 5.5
−
0.3 to + 7.2
−
0.3 to V
CC
or
V
C
+ 0.3
10
Unit
V
mA
A
mJ
V
V
V
mA
P
D
R
qJA
P
D
R
qJA
P
D
R
qJA
T
J
T
A
862
145
702
178
1.25
100
+150
0 to 70
−
25 to + 85
−40
to +85
−40
to +105
−
65 to +150
mW
°C/W
mW
°C/W
W
°C/W
°C
°C
T
stg
°C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. This device series contains ESD protection and exceeds the following tests:
Human Body Model 4000 V per JEDEC Standard JESD22-A114B
Machine Model Method 200 V per JEDEC Standard JESD22-A115-A
2. This device contains latch-up protection and exceeds 100 mA per JEDEC Standard JESD78
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2
UC3842B, UC3843B, UC2842B, UC2843B
ELECTRICAL CHARACTERISTICS
(V
CC
= 15 V [Note 3], 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 4], unless otherwise noted.)
UC284XB, UC2843D
Characteristics
REFERENCE SECTION
Reference Output Voltage (I
O
= 1.0 mA, T
J
= 25°C)
Line Regulation (V
CC
= 12 V to 25 V)
Load Regulation (I
O
= 1.0 mA to 20 mA)
Temperature Stability
Total Output Variation over Line, Load, and Temperature
UC284XB
UC2843D
Output Noise Voltage (f = 10 Hz to 10 kHz, T
J
= 25°C)
Long Term Stability (T
A
= 125°C for 1000 Hours)
Output Short Circuit Current
OSCILLATOR SECTION
Frequency
T
J
= 25°C
T
A
= T
low
to T
high
T
J
= 25°C (R
T
= 6.2 k, C
T
= 1.0 nF)
Frequency Change with Voltage (V
CC
= 12 V to 25 V)
Frequency Change with Temperature, T
A
= T
low
to T
high
Oscillator Voltage Swing (Peak−to−Peak)
Discharge Current (V
OSC
= 2.0 V)
T
J
= 25°C, T
A
= T
low
to T
high
f
OSC
49
48
225
−
−
−
7.8
7.5
−
2.45
2.42
−
65
0.7
60
2.0
−
0.5
5.0
−
−
52
−
250
0.2
1.0
1.6
8.3
−
−
2.5
2.5
−
0.1
90
1.0
70
12
−1.0
6.2
0.8
−
55
56
275
1.0
−
−
8.8
8.8
−
2.55
2.58
−1.0
−
−
−
−
−
−
1.1
−
49
48
225
−
−
−
7.8
7.6
7.2
2.42
−
65
0.7
60
2.0
−
0.5
5.0
−
−
52
−
250
0.2
0.5
1.6
8.3
−
−
2.5
−
0.1
90
1.0
70
12
−1.0
6.2
0.8
0.8
55
56
275
1.0
−
−
8.8
8.8
8.8
2.58
−
2.0
−
−
−
−
−
−
1.1
1.2
kHz
V
ref
Reg
line
Reg
load
T
S
V
ref
4.95
−
−
−
4.9
4.82
−
−
−
30
5.0
2.0
3.0
0.2
−
−
50
5.0
−
85
5.05
20
25
−
5.1
5.18
−
−
−180
4.9
−
−
−
4.82
−
−
−
30
5.0
2.0
3.0
0.2
−
50
5.0
−
85
5.1
20
25
−
5.18
−
−
−180
V
mV
mV
mV/°C
V
Symbol
Min
Typ
Max
UC384XB, XBV
Min
Typ
Max
Unit
V
n
S
I
SC
mV
mV
mA
Df
OSC
/DV
Df
OSC
/DT
V
OSC
I
dischg
%
%
V
mA
UC284XB, UC384XB
UC2843D, UC384XBV
UC284XB
UC2843D
V
FB
I
IB
A
VOL
BW
PSRR
I
Sink
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
UC2843D, UC384XBV
V
mA
dB
MHz
dB
mA
I
Source
V
OH
V
OL
V
3. Adjust V
CC
above the Startup threshold before setting to 15 V.
4. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
T
low
= 0°C for UC3842B, UC3843B;
−25°C
for UC2842B, UC2843B;
−40°C
for UC3842BV, UC3843BV, UC2843D
T
high
= +70°C for UC3842B, UC3843B; +85°C for UC2842B, UC2843B, UC2843D; +105°C for UC3842BV, UC3843BV
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3
UC3842B, UC3843B, UC2842B, UC2843B
ELECTRICAL CHARACTERISTICS
(V
CC
= 15 V [Note 7], R
T
= 10 k, C
T
= 3.3 nF. For typical values T
A
= 25°C, for min/max values
UC284XB, UC2843D
Characteristics
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 5 and 6)
UC2843D, UC284XB, UC384XB
UC384XBV
Maximum Current Sense Input Threshold (Note 5)
UC2843D, UC284XB, UC384XB
UC384XBV
Power Supply Rejection Ratio (V
CC
= 12 V to 25 V, Note 5)
Input Bias Current
Propagation Delay (Current Sense Input to Output)
OUTPUT SECTION
Output Voltage
Low State (I
Sink
= 20 mA)
(I
Sink
= 200 mA)
High State
(I
Source
= 20 mA)
(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 (V
CC
)
UCX842B, BV
UCX843B, BV, D
UCX842B, BV
UCX843B, BV, D
V
th
15
7.8
9.0
7.0
16
8.4
10
7.6
17
9.0
11
8.2
14.5
7.8
8.5
7.0
16
8.4
10
7.6
17.5
9.0
11.5
8.2
V
V
OL(UVLO)
t
r
t
f
V
OL
V
OH
−
−
−
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
13.5
13.4
0.1
50
50
0.4
2.2
2.3
−
−
−
1.1
150
150
V
A
V
2.85
−
0.9
−
−
−
−
3.0
−
1.0
−
70
−
2.0
150
3.15
−
1.1
−
−
−10
300
2.85
2.85
0.9
0.85
−
−
−
3.0
3.0
1.0
1.0
70
−
2.0
150
3.15
3.25
1.1
1.1
−
−10
300
V/V
Symbol
Min
Typ
Max
UC384XB, XBV
Min
Typ
Max
Unit
T
A
is the operating ambient temperature range that applies [Note 8], unless otherwise noted.)
V
th
V
PSRR
I
IB
t
PLH(In/Out)
dB
mA
ns
UC284XB, UC384XB
UC384XBV, UC2843D
UC284XB, UC384XB
UC384XBV, UC2843D
V
ns
ns
Minimum Operating Voltage After Turn−On (V
CC
)
V
CC(min)
V
PWM SECTION
Duty Cycle
Maximum UC284XB, UC384XB, UC2843D
Maximum
UC384XBV
Minimum
TOTAL DEVICE
Power Supply Current
Startup (V
CC
= 6.5 V for UCX843B, UC2843D
Startup
V
CC
14 V for UCX842B, BV)
(Note 7)
Power Supply Zener Voltage (I
CC
= 25 mA)
5. This parameter is measured at the latch trip point with V
FB
= 0 V.
6. Comparator gain is defined as: A
V
DV
Output Compensation
7. Adjust V
CC
above the Startup threshold before setting to 15 V.
8. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
T
low
= 0°C for UC3842B, UC3843B;
−25°C
for UC2842B, UC2843B;
−40°C
for UC3842BV, UC3843BV, UC2843D
T
high
= +70°C for UC3842B, UC3843B; +85°C for UC2842B, UC2843B, UC2843D; +105°C for UC3842BV, UC3843BV
DV
Current Sense Input
DC
(max)
DC
(min)
94
−
−
96
−
−
−
−
0
94
93
−
96
96
−
−
−
0
%
I
CC
+ I
C
−
−
0.3
12
36
0.5
17
−
−
−
30
0.3
12
36
0.5
17
−
mA
V
Z
30
V
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4
UC3842B, UC3843B, UC2842B, UC2843B
80
% DT, PERCENT OUTPUT DEADTIME
50
R T, TIMING RESISTOR (k
Ω
)
20
8.0
5.0
2.0
0.8
10 k
V
CC
= 15 V
T
A
= 25°C
20 k
50 k
100 k
200 k
500 k
f
OSC
, OSCILLATOR FREQUENCY (kHz)
1.0 M
100
1. C
T
= 10 nF
50 2. C
T
= 5.0 nF
3. C
T
= 2.0 nF
4. C
T
= 1.0 nF
20 5. C
T
= 500 pF
6. C
T
= 200 pF
10 7. C
T
= 100 pF
5.0
2.0
1.0
10 k
20 k
4
3
2
1
5
6
7
V
CC
= 15 V
T
A
= 25°C
50 k
100 k
200 k
500 k
f
OSC
, OSCILLATOR FREQUENCY (kHz)
1.0 M
Figure 2. Timing Resistor
versus Oscillator Frequency
Figure 3. Output Deadtime
versus Oscillator Frequency
9.0
I dischg , DISCHARGE CURRENT (mA)
V
CC
= 15 V
V
OSC
= 2.0 V
8.5
D max , MAXIMUM OUTPUT DUTY CYCLE (%)
100
90
80
70
60
50
40
0.8
I
dischg
= 8.54 mA
8.0
7.5
V
CC
= 15 V
C
T
= 3.3 nF
T
A
= 25°C
1.0
2.0
3.0
4.0
R
T
, TIMING RESISTOR (kW)
5.0 6.0 7.0 8.0
7.0
- 55
- 25
0
25
50
75
T
A
, AMBIENT TEMPERATURE (°C)
100
125
Figure 4. Oscillator Discharge Current
versus Temperature
Figure 5. Maximum Output Duty Cycle
versus Timing Resistor
2.55 V
V
CC
= 15 V
A
V
= -1.0
T
A
= 25°C
20 mV/DIV
3.0 V
V
CC
= 15 V
A
V
= -1.0
T
A
= 25°C
20 mV/DIV
1.0
ms/DIV
2.50 V
2.5 V
2.45 V
0.5
ms/DIV
2.0 V
Figure 6. Error Amp Small Signal
Transient Response
Figure 7. Error Amp Large Signal
Transient Response
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5
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