a4403geu-t Allegro MicroSystems, Inc., a4403geu-t Datasheet - Page 13

• Manufacturer Part Number: a4403geu-t
• Description: Valley Current Mode Control Buck Converter
• Manufacturer: Allegro MicroSystems, Inc.

To avoid ground offset issues in the output voltage, it is highly
recommended that the ground-referenced feedback resistor R6
should be connected directly to the GND connection of the
A4403. In other words, the R6 ground return should avoid the use
of the internal ground plane.
All ground-referenced support components (C5 and the DIS
switch) should also be located as close to the GND connection as
possible. A “local quiet” ground plane around these components
can be implemented; however, this ground plane should have a
high impedance connection to the star ground connection of the
power stages, as referenced below.
The sense resistor connections should be connected in a Kelvin
circuit (see figure 3) to the corresponding pins on the A4403
A4403
Figure 5. FET on-cycle current conduction paths
Input
Voltage
C
IN
VIN
Q
Star Connection
Figure 4. Ground plane configurations
R
Local ‘quiet’
Ground Plane
LX
D
A4403 Support
Components
Switch
C
OUT
L
C5
Valley Current Mode Control Buck Converter
R6
V
R
OUT
LOAD
GND
A4403
SGND
Thermal Vias
(ISEN and SGND). Note that it is imperative that the PCB traces
between the sense resistor pads and the sense connections are as
short as possible to minimize the effects of leakage inductance.
In noisy systems, it is highly recommended that an R-C filter be
used to filter the signal produced across the ISEN pin. See the
Sense Resistor section and the Typical Application schematic.
If an internal ground plane is used, it is recommended that it
does not overlap the switching node, LX, to avoid the possibility
of noise pick up. To minimize the possibility of noise injection
issues, it is recommended to isolate the ground plane around the
high impedance nodes, such as FB and SS.
Figure 6. FET off-cycle current conduction paths
Input
Voltage
Power Circuitry
Cin
R
D
C
Star Connection
IN
Internal Ground Plane
Cout
VIN
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
Q
Star Connection
R
LX
D
C
OUT
L
R
V
LOAD
OUT
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