MIC4685WREV MICREL [Micrel Semiconductor], MIC4685WREV Datasheet - Page 12

• Manufacturer Part Number: MIC4685WREV
• Description: 3A SPAK SuperSwitcher Buck Regulator
• Manufacturer: MICREL [Micrel Semiconductor]

Layout Considerations
Layout is very important when designing any switching
regulator. Rapidly changing currents, through the printed
circuit board traces and stray inductance, can generate
voltage transients which can cause problems.
To minimize stray inductance and ground loops, keep
trace lengths as short as possible. For example, keep
D1 close to pin 6 and pin 4, and Tab, keep L1 away from
sensitive node FB, and keep C
and Tab. See “ Applications Information: Thermal
Considerations ” for ground plane layout.
The feedback pin should be kept as far way from the
switching elements (usually L1 and D1) as possible.
A circuit with sample layouts are provided. See Figure 6.
Gerber files are available upon request.
Micrel, Inc.
January 2010
IN
(34V transient)
+4V to +30V
close to pin 2 and pin 4,
7-pin
SPAK
V
IN
C
IN
Figure 2. Critical Traces for Layout
2
5
IN
EN
MIC4685_R
GND
4,Tab
4, Tab
SW
BS
FB
1
6
3
12
D1
Bootstrap Diode
The bootstrap diode provides an external bias source
directly to the main pass element, this reduces V
allowing the MIC4685 to be used in very low head-room
applications i.e., 5V
Bootstrap diode not for use if V
Figure 2.
39µH
L1
C
OUT
R1
R2
V
GND
OUT
IN
to 3.3V
OUT
IN
exceeds 16V, V
with high efficiencies.
M9999-012610
MIC4685
SAT
IN
. See
thus