ml4894 Microsemi Corporation, ml4894 Datasheet - Page 9

• Manufacturer Part Number: ml4894
• Description: Synchronous Buck Controller
• Manufacturer: Microsemi Corporation

LAYOUT
A typical application circuit is shown in Figure 6.
Proximity of passive devices and adequate power and
ground planes are critical for reliable operation of the
circuit. In general, use the top layer for the high current
connections and the bottom layer for the quiet
connections such as GND, feedback and current sense.
Some more specific guidelines follow.
1. The connection from the current sense resistor to the
2. The trace lengths from the buck regulator’s input
3. The high current ground paths need to be kept separate
I
located as close to the lead of the resistor as possible.
The trace length from the sense resistor to the ML4894
should be kept as short as possible and away from
switching components and their traces.
capacitor to the switching MOSFET, from the MOSFETs
to the inductor, from the synchronous rectifier MOSFET
to the sense resistor, and from the inductor to the
output capacitor should all be as short as possible.
from the signal ground paths. The GND connection
should be made at a single-point star ground. It is very
important that the ground for the ML4894 ground pin
(pin 5) be made using a separate trace.
SENSE
V IN
pin should be made by a separate trace and
22 F
C1
1 F
C4
22 F
C2
22 F
C3
1
2
3
4
V REG
V FB
I SENSE
SHDN
Figure 6. 5V, 3A DC/DC Converter Circuit
ML4894
N DRV
P DRV
GND
V IN
8
7
6
5
IRF7403
IRF7406
Q2
Q1
4. Concentrating on keeping the current sense and high
5. The V
6. Remote sensing the output for improved load
current connections short as well as keeping the
switching components and traces away from the
sensitive analog components and traces during layout
will eliminate the majority of problems created by a
poor layout.
close to the ML4894 for adequate filtering of the IC’s
internal bias voltage.
regulation can be implemented with the ML4894. The
output can be remote sensed by using the top of the
external resistor divider as the remote sense point.
REG
25m
R1
39 H
and bypass capacitor needs to be located
L1
100 F
C6
100 F
C7
100 F
C8
ML4894
V OUT
+
–
5V
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