ꢀꢁꢂ ꢃ ꢄ ꢃ ꢅ ꢀ ꢁꢂ ꢃꢄ ꢃꢆ
ꢀꢁꢄ ꢃ ꢄ ꢃ ꢅ ꢀ ꢁꢄ ꢃꢄ ꢃꢆ
SLUS221A – APRIL 2000 – REVISED MAY 2001
ꢇ ꢆꢈ ꢉꢊꢋ ꢌꢁ ꢆꢇ ꢍꢎ ꢌꢏ ꢌꢊ ꢐ
ꢁꢑ ꢉꢋ ꢐꢑ ꢎ ꢎꢊ ꢐ
FEATURES
DESCRIPTION
D
Independent 1% Reference
The UC3838 and the UC3838A family of magnetic
amplifier controllers contains the circuitry to
generate and amplify a low-level analog error
signal along with a high voltage-compliant current
source. This source provides the reset current
necessary to enable a magnetic amplifier to
regulate and control a power supply output in the
range of 2 A to 20 A.
D
Two Uncommitted, Identical Operational
Amplifiers
D
100-mA Reset Current Source With –120-V
Capability
D
5-V to 40-V Analog Operation
5-W DIP Package
D
The UC3838A originally was a parametric
improvement version of the UC3838 which since
has been used for both versions. There is no
difference between the UC3838A and UC3838
version.
BLOCK DIAGRAM
VCC 10
11 VM
By controlling the reset current to a magnetic
amplifier, this device defines the amount of
volt-seconds the magnetic amplifier blocks before
switching to the conducting state. Magnetic
amplifiers are ideal for post-regulators for
multiple-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
blocks a portion of this input waveform, allowing
just enough to pass to provide a regulated output.
With the UC3838/A, only the magnetic amplifier
coil, three diodes, and an output L-C filter are
necessary to implement a complete closed-loop
regulator.
2.5 V
REFERENCE
VREF
9
Ω
Ω
Ω
20
5 k
1 k
3.5 V
INV. IN
6
–
E/A
+
N.I. IN
E/A OUT
INV. IN
7
8
3
14 RESET
15 DR 1
16 DR 2
–
C/L
+
N.I. IN
2
1
C/L OUT
4
5
12
13
GND GND GND GND
UDG-97174
AVAILABLE OPTIONS
Packaged Devices
T
A
= T
J
SOIC Wide
(DW)
PDIP (N)
PLCC (Q)
UC2838DW
UC2838ADW
UC3838DW
UC3838ADW
UC2838N
UC2838AN
UC3838N
UC3838AN
UC2838Q
UC2838AQ
UC3838Q
UC3838AQ
–20°C to 85°C
0°C to 70°C
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