A8447
High Voltage Step Down Regulator
Features and Benefits
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Wide input voltage range: 8 to 50 V
Integrated low R
DS(on)
DMOS switch
3 A continuous output current
Adjustable fixed off-time
Highly efficient
Adjustable output: 0.8 to 24 V
Small package with exposed thermal pad
Description
The A8447 is a 3 A, high efficiency general-purpose buck
regulator designed for a wide variety of applications. The output
voltage is adjustable from 0.8 to 24 V, based on a resistor divider
and the 0.8 V ± 3 % reference. External components include an
external clamping diode, inductor, and filter capacitor. The off-
time is determined by an external resistor to ground. It operates
in both continuous and discontinuous modes to maintain light
load regulation. An internal blanking circuit is used to filter
out transients due to the reverse recovery of the external clamp
diode. Typical blanking time is 200 ns.
This new device is ideal for various end products including
applications with 8 to 50 V input voltage range and require up
to 3 A output current, such as uninterruptible power supplies,
point of sale (POS) applications, and industrial applications
with 24 or 36 V bus.
Applications include:
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Printer power supplies
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Office automation equipment
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POS thermal, laser, photo, and inkjet printers
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Tape drives
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Industrial applications
Package: 8 pin SOIC with exposed thermal
pad (suffix LJ)
Approximate Scale 1:1
Typical Application
+42
V
CBOOT
0.01 μF
CIN2
BOOT
VIN
CIN1
0.22 μF
Efficiency vs. Output Current
90.0
88.0
86.0
84.0
82.0
80.0
78.0
76.0
74.0
72.0
70.0
0
500
1000
1500
2000
ENB
A8447
LX
L1
TSET
RTSET
54 k
GND
VBIAS
R1
2.87 k
FB
R2
910
CBYP
0.22 μF
V
OUT
3.3 V
3A
Efficiency %
D1
ESR
COUT
220 μF
25 V
V
OUT
(V)
5
3.3
2500
3000
I
OUT
(mA)
Data is for reference only. Efficiency data from circuit shown in left panel.
A8447-DS, Rev. 1
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
