LIN D
O C
#:
1840
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O VA T I O N
P
R O D U C T I O N
D
A T A
S
H E E T
DESCRIPTION
The UC184xA family of control ICs
provides all the necessary features to
implement off-line fixed-frequency,
current-mode switching power supplies
with a minimum of external compo-
nents. The current mode architecture
demonstrates improved load regulation,
pulse-by-pulse current limiting and
inherent protection of the power supply
output switch. The IC includes: A
bandgap reference trimmed to ±1%
accuracy, an error amplifier, a current
sense comparator with internal clamp to
1V, a high current totem pole output
stage for fast switching of power
MOSFET's, and an externally program-
mable oscillator to set frequency and
maximum duty cycle. The under-
voltage lock-out is designed to operate
with 250µA typ. start-up current,
allowing an efficient bootstrap supply
voltage design. Available options for
this family of products, such as start-up
voltage hysteresis and duty cycle, are
summarized below in the Available
Options section. The UC184xA family
of control ICs is also available in 14-pin
SOIC package which makes the Power
Output Stage Collector and Ground pins
available.
K E Y F E AT U R E S
s
LOW START-UP CURRENT.
(0.5mA max.)
s
TRIMMED OSCILLATOR DISCHARGE
CURRENT.
(See Product Highlight)
p
OPTIMIZED FOR OFF-LINE AND DC-TO-DC
CONVERTERS.
p
AUTOMATIC FEED FORWARD
COMPENSATION.
p
PULSE-BY-PULSE CURRENT LIMITING.
p
ENHANCED LOAD RESPONSE
CHARACTERISTICS.
p
UNDER-VOLTAGE LOCKOUT WITH
HYSTERESIS.
p
DOUBLE PULSE SUPPRESSION.
p
HIGH-CURRENT TOTEM POLE OUTPUT.
p
INTERNALLY TRIMMED BANDGAP
REFERENCE.
p
500KHz OPERATION.
p
LOW R
O
ERROR AMPLIFIER.
PRODUCT HIGHLIGHT
C
OMPARISON
OF
UC384
X
A
VS
.
SG384
X
D
ISCHARGE
C
URRENT
A P P L I C AT I O N S
SG384x
Max. Limit
UC384xA
SG384x
Min. Limit
T
A
=25°C
s
ECONOMICAL OFF-LINE FLYBACK OR
FORWARD CONVERTERS.
s
DC-DC BUCK OR BOOST CONVERTERS.
s
LOW COST DC MOTOR CONTROL.
A
V A I L A B L E
O
P T I O N S
Part #
UCx842A
UCx843A
7.5
7.8
8.3
Mean
8.8
9.3
Start-Up Hysteresis Max. Duty
Voltage
Cycle
16V
8.4V
16V
8.4V
6V
0.8V
6V
0.8V
<100%
<100%
<50%
<50%
−3σ
+3σ
UCx844A
UCx845A
Discharge Current Distribution - mA
PA C K A G E O R D E R I N F O R M AT I O N
T
A
(°C)
0 to 70
-40 to 85
-55 to 125
M
Plastic DIP
8-pin
UC384xAM
UC284xAM
—
DM
Plastic SOIC
8-pin
UC384xADM
UC284xADM
—
D
Plastic SOIC
14-pin
UC384xAD
UC284xAD
—
Y
Ceramic DIP
8-pin
—
UC284xAY
UC184xAY
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. UC3842ADMT)
F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
Copyright © 1995
Rev. 1.2 12/95
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841
1
PRODUCT DATABOOK 1996/1997
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
A B S O L U T E M A X I M U M R AT I N G S
(Note 1)
PACKAGE PIN OUTS
COMP
V
FB
I
SENSE
R
T
/C
T
1
2
3
4
8
7
6
5
Supply Voltage (Low Impedance Source) (V
CC
) ......................................................... 30V
Supply Voltage (I
CC
< 30mA) .......................................................................... Self Limiting
Output Current ............................................................................................................. ±1A
Output Energy (Capacitive Load) ................................................................................. 5µJ
Analog Inputs (V
FB
& I
SENSE
) ........................................................................ -0.3V to +6.3V
Error Amp Output Sink Current ............................................................................... 10mA
Power Dissipation at T
A
= 25°C (M Package) .............................................................. 1W
Storage Temperature Range .................................................................... -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) ............................................................. 300°C
Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect
to Ground. Currents are positive into, negative out of the specified terminal. Pin
numbers refer to DIL packages only.
V
REF
V
CC
OUTPUT
GND
M & Y PACKAGE
(Top View)
COMP
V
FB
I
SENSE
R
T
/C
T
1
2
3
4
8
7
6
5
V
REF
V
CC
OUTPUT
GND
T H ER MAL DATA
M PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
DM PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
D PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
Y PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
130°C/W
120°C/W
165°C/W
95°C/W
COMP
N.C.
V
FB
N.C.
I
SENSE
N.C.
R
T
/C
T
DM PACKAGE
(Top View)
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
REF
N.C.
V
CC
V
C
OUTPUT
GND
PWR GND
D PACKAGE
(Top View)
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow
2
Copyright © 1995
Rev. 1.2 12/95
PRODUCT DATABOOK 1996/1997
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for UC384xA with 0°C
≤
T
A
≤
70°C, UC284xA with -40°C
≤
T
A
≤
85°C,
UC184xA with -55°C
≤
T
A
≤
125°C; V
CC
=15V; R
T
=10K; C
T
=3.3nF. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal
to the ambient temperature.)
Parameter
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Stability (Note 2 & 7)
Total Output Variation
Output Noise Voltage (Note 2)
Long Term Stability (Note 2)
Output Short Circuit Current
Symbol
Test Conditions
UC184xA/284xA
UC384xA
Units
Min. Typ. Max. Min. Typ. Max.
4.95 5.00 5.05 4.90 5.00 5.10
6
20
6
20
6
25
6
25
0.2 0.4
0.2 0.4
4.9
5.1 4.82
5.18
50
50
5
25
5
25
-30 -100 -180 -30 -100 -180
47
52
0.2
5
1.7
8.3
57
1
47
52
0.2
5
1.7
8.3
57
1
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
V
REF
T
J
= 25°C, I
L
= 1mA
12
≤
V
IN
≤
25V
1
≤
I
O
≤
20mA
Over Line, Load, and Temperature
10Hz
≤
f
≤
10kHz, T
J
= 25°C
T
A
= 125°C, t = 1000hrs
V
N
I
SC
Oscillator Section
Initial Accuracy (Note 6)
Voltage Stability
Temperature Stability (Note 2)
Amplitude (Note 2)
Discharge Current
T
J
= 25°C
12
≤
V
CC
≤
25V
T
MIN
≤
T
A
≤
T
MAX
T
J
= 25°C, V
PIN 4
= 2V
V
PIN 4
= 2V, T
MIN
≤
T
A
≤
T
MAX
V
PIN 1
= 2.5V
I
B
A
VOL
UGBW
PSRR
I
OL
I
OH
V
OH
V
OL
A
VOL
PSRR
I
B
T
pd
V
PIN 1
= 5V
12
≤
V
CC
≤
25V
V
PIN 3
= 0 to 2V
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
T
J
= 25°C, C
L
= 1nF
T
J
= 25°C, C
L
= 1nF
V
CC
= 5V, I
SINK
= 10mA
2
≤
V
O
≤
4V
T
j
= 25°C
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 V
REF
7.8
7.5
8.8
8.8
7.8
7.6
8.8
8.8
Error Amp Section
Input Voltage
Input Bias Current
Open Loop Gain
Unity Gain Bandwidth (Note 2)
Power Supply Rejection Ratio (Note 3)
Output Sink Current
Output Source Current
Output Voltage High Level
Output Voltage Low Level
2.45 2.50 2.55 2.42 2.50 2.58
-0.3
-1
-0.3
-2
65
90
65
90
0.7
1
0.7
1
60
70
60
70
2
6
2
6
-0.5 -0.8
-0.5 -0.8
5
6
5
6
0.7 1.1
0.7 1.1
2.85
0.9
3
1
70
-2
150
0.1
1.5
13.5
13.5
50
50
0.7
3.15 2.85
1.1 0.9
-10
300
0.4
2.2
13
12
150
150
1.2
3
1
70
-2
150
0.1
1.5
13.5
13.5
50
50
0.7
3.15
1.1
-10
300
0.4
2.2
Current Sense Section
Gain (Note 3 & 4)
Maximum Input Signal (Note 3)
Power Supply Rejection Ratio (Note 3)
Input Bias Current
Delay to Output (Note 2)
Output Section
Output Low Level
Output High Level
Rise Time (Note 2)
Fall Time (Note 2)
UVLO Saturation
V
OL
V
OH
T
R
T
F
V
SAT
13
12
150
150
1.2
(El ectrical Char acteris tics continu e next page.)
Copyright © 1995
Rev. 1.2 12/95
3
PRODUCT DATABOOK 1996/1997
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
ELECTRICAL CHARACTERISTICS
Parameter
Under-Voltage Lockout Section
Start Threshold
Min. Operation Voltage After Turn-On
x842A/4A
x843A/5A
x842A/4A
x843A/5A
x842A/3A
x844A/5A
(Con't.)
Symbol
Test Conditions
UC184xA/284xA
UC384xA
Units
Min. Typ. Max. 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
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
PWM Section
Maximum Duty Cycle
Minimum Duty Cycle
Total Standby Section
Start-Up Current
Operating Supply Current
Zener Voltage
I
CC
V
Z
0.3
11
35
0.3
11
35
I
CC
= 25mA
30
Notes: 2. These parameters, although guaranteed, are not 100% tested in
production.
3. Parameter measured at trip point of latch with V
VFB
= 0.
4. Gain defined as: A
VOL
=
∆
V
COMP
; 0
≤
V
ISENSE
≤
0.8V.
∆
V
ISENSE
7. "Temperature stability, sometimes referred to as average temperature
coefficient, is described by the equation:
V
REF
(max.) - V
REF
(min.)
Temp Stability =
T
J
(max.) - T
J
(min.)
V
REF
(max.) & V
REF
(min.) are the maximum & minimum reference
voltage measured over the appropriate temperature range. Note that
the extremes in voltage do not necessarily occur at the extremes in
temperature."
5. Adjust V
CC
above the start threshold before setting at 15V.
6. Output frequency equals oscillator frequency for the UC1842A
and UC1843A. Output frequency is one half oscillator frequency
for the UC1844A and UC1845A.
BLOCK DIAGRAM
V
CC
*
34V
UVLO
Hysteresis
6V (1842A/4A)
0.8V (1843A/5A)
GROUND
**
UVLO
16V (1842A/4A)
8.4V (1843A/5A)
2.5V
S/R
5V
Ref
Internal
Bias
V
REF
5.0V
50mA
V
REF
Good Logic
R
T
/C
T
Oscillator
***
Error Amp
V
FB
COMP
CURRENT SENSE
2R
R
1V
S
R
Current Sense
Comparator
PWM
Latch
T
*
V
C
OUTPUT
**
POWER GROUND
* - V
CC
and V
C
are internally connected for 8 pin packages.
** - POWER GROUND and GROUND are internally connected for 8 pin packages.
*** - Toggle flip flop used only in x844A and x845A series.
4
Copyright © 1995
Rev. 1.2 12/95
PRODUCT DATABOOK 1996/1997
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
CHARACTERISTIC CURVES
FIGURE 1.
— OSCILLATOR FREQUENCY vs. TIMING
RESISTOR
V
REF
8
Oscillator Frequency - (Hz)
1M
C
T
= 1nF
R
T
R
T
/C
T
4
C
T
GROUND 5
C
T
= 2.2nF
100k
10k
C
T
= 4.7nF
For R
T
> 5k, f
»
0
300
1.0k
3.0k
10.0k
30.0k
100k
1.72
R
T
C
T
Note: Output drive frequency is half the oscillator frequency for
the UCx844A/5A devices.
R
T
- (ohms)
FIGURE 2.
— MAXIMUM DUTY CYCLE vs. TIMING RESISTOR
100.0
Maximum Duty Cycle - (%)
80.0
60.0
40.0
20.0
0
300
1.0k
3.0k
10.0k
30.0k
100k
R
T
- (ohms)
Copyright © 1995
Rev. 1.2 12/95
5
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