UC1838A
UC2838A
UC3838A
Magnetic Amplifier Controller
FEATURES
Independent 1% Reference
Two Uncommitted, Identical
Operational Amplifiers
100mA Reset Current Source
with 120V Capability
5V to 40V Analog Operation
5W DIL Package
10
VCC
VREF
9
2.5V
REFERENCE
INV. IN
8
E/A OUT
3
INV. IN
6
7
N.I. IN
2
1
N.I. IN
C/L OUT
C/L
E/A
3.5V
15 DR 1
16 DR 2
RESET
14
VM
11
5
12
13
4
GND GND GND GND
20
1k
5k
BLOCK DIAGRAM
04/99
UDG-97174
DESCRIPTION
The UC1838A family of magnetic amplifier controllers contains the circuitry to gen-
erate and amplify a low-level analog error signal along with a high volt-
age-compliant current source. This source will provide the reset current necessary
to enable a magnetic amplifier to regulate and control a power supply output in the
range of 2A to 20A.
By controlling the reset current to a magnetic amplifier, this device will define the
amount of volt-seconds the magnetic amplifier will block before switching to the
conducting state. Magnetic amplifiers are ideal for post-regulators for multi-
ple-output power supplies where each output can be independently controlled with
efficiencies up to 99%. With a square or pulse-width-modulated input voltage, a
magnetic amplifier will block a portion of this input waveform, allowing just enough
to pass to provide a regulated output. With the UC1838A, only the magnetic ampli-
fier coil, three diodes, and an output L-C filter are necessary to implement a com-
plete closed-loop regulator.
The UC1838A contains a precision 2.5V reference, two uncommitted high-gain op
amps and a high-gain PNP-equivalent current source which can deliver up to
100mA of magnetic amplifier reset current and with 120 volt capability.
These devices are available in a plastic "bat-wing" DIP for operation over a 20C
to +85C temperature range and, with reduced power, in a hermetically sealed
cerdip for 55C to +125C operation. Surface mount versions are also available.
This improved "A" version replaced the non "A" version formerly introduced.
2
UC1838A
UC2838A
UC3838A
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
40V
Magnetic Amp. Source Voltage, V
M . . . . . . . . . . . . . . . . . . . . . . . .
40V
Reset Output Voltage, V
R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
120V
Total Current Source Voltage, V
M
- V
R . . . . . . . . . . . . . . . . . .
140V
Amplifier Input Range . . . . . . . . . . . . . . . . . . . . . . 0.3V to V
CC
Reset Input Current, I
DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10mA
Power Dissipation at T
A
= 25C
Q, N, DP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W
J, L Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W
Power Dissipation at T (leads/case) = 25C
Q, N, DP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5W
J, L Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W
Operating Temperature Range . . . . . . . . . . . . 55C to +125C
Storage Temperature Range . . . . . . . . . . . . . 65C to +150C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . . 300C
Note: All voltages are with respect to ground pins. All currents
are positive into the specified terminal. Consult Packaging
section of Databook for thermal limitations and considerations
of package.
DR 2
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
DR 1
Reset
Gnd
Gnd
V
M
V
CC
V
REF
C/L Out
C/L N.I. In
C/L INV. In
Gnd
Gnd
E/A Inv. In
E/A N.I. In
E/A Out
CONNECTION DIAGRAMS
DIL-16, SOIC-16 (TOP VIEW)
J or N Package, DP Package
3
18
17
16
N/C
1
2
20 19
15
14
4
5
6
7
8
9
11
10
12 13
C/L Out
C/L N.I. In
DR2
DR1
Reset
N/C
N/C
GND
V
M
C/L Inv. In
GND
N/C
N/C
E/A Inv. In
V
CC
V
REF
N/C
E/A N.I. In
E/A Out
PLCC-20, LCC-20 (TOP VIEW)
Q, L Packages
Note: All four ground pins must be connected to a common
ground
TEMPERATURE RANGE
PACKAGE
UC1838AJ
55
C to +125
C
Ceramic Dip
UC1838AL
CLCC
UC2838ADP
20
C to +85
C
Power SOIC
UC2838AN
Plastic Dip
UC2838AQ
PLCC
UC3838ADP
0
C to +70
C
Power SOIC
UC3838AN
Plastic Dip
UC3838AQ
PLCC
ORDERING INFORMATION
3
UC1838A
UC2838A
UC3838A
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for T
A
= 55C to +125C for the
UC1838A, 20C to +85C for the UC2838A, and 0C to +70C for the UC3838A, V
CC
= 20V, V
M
= 5V, T
A
= T
J.
PARAMETER
TEST CONDITIONS
UC1838A / UC2838A
UC3838A
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
Reference Section
Supply Current
V
CC
= V
M
= 40V
4
8
4
8
mA
Reference Output
T
A
= 25C
2.47
2.5
2.53
2.45
2.5
2.55
V
Line Regulation
V
CC
= 5 to 30V
1
5
1
10
mV
Load Regulation
I
O
= 0 to 2mA
5
20
5
20
mV
Short Circuit Current
V
REF
= 0V
30
60
30
60
mA
Temperature Stability*
Over Operating Temp. Range
15
25
10
25
mV
Amplifier Section (Each Amplifier)
Offset Voltage
V
CM
= 2.5V
5
10
mV
Input Bias Current
V
IN
= 0V
1
1
A
Input Offset Current
100
100
nA
Minimum Output Swing
0.4
18
0.4
18
V
Output Sink Current
V
O
= 5V
1
10
30
1
10
30
mA
Output Source Current
V
O
= 0V
1
10
20
1
10
20
mA
A
VOL
V
O
= 1 to 11V
100
120
100
120
dB
C
MRR
V
IN
= 1 to 11V
70
80
70
80
dB
P
SRR
V
CC
= 10 to 20V
70
100
70
100
dB
Gain Bandwidth*
0.6
0.8
0.6
0.8
MHz
Reset Drive Section
Input Leakage
V
DR
= 40V
10
10
A
Output Leakage
V
R
= 120V
100
100
A
Input Current
I
R
= 50mA
1
2
1
2
mA
Maximum Reset Current
I
DR
= 3mA
100
120
200
100
120
200
mA
Transconductance
I
R
= 10 to 50mA
.03
.042
.055
.03
.042
.055
A/V
* These parameters are guaranteed by design but not 100% tested in production.
TYPICAL APPLICATION
+12V, 4A output with switching frequency = 50 kHz.
4
UC1838A
UC2838A
UC3838A
APPLICATION INFORMATION
Figure 1. Amplifier open loop response.
Figure 2. Reset driver-input current.
Figure 5. Reset driver-input voltage.
Figure 3. Reset driver-output impedance.
Figure 6. Reference temperature coefficient.
UNITRODE CORPORATION
7 CONTINENTAL BLVD. MERRIMACK, NH 03054
TEL. (603) 424-2410 FAX (603) 424-3460
Figure 4. Reset driver response.
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Copyright
1999, Texas Instruments Incorporated
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