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| LTC3371_15 Datasheet, PDF (20/26 Pages) Linear Technology – 4-Channel 8A Configurable Buck DC/DCs with Watchdog and Power-On Reset | |||
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LTC3371
Applications Information
PCB Considerations
When laying out the printed circuit board, the following list
should be followed to ensure proper operation of the LTC3371:
1. The exposed pad of the package (Pin 39) should connect
directly to a large ground plane to minimize thermal and
electrical impedance.
2. Each of the input supply pins should have a decoupling
capacitor.
3. The connections to the switching regulator input supply
pins and their respective decoupling capacitors should
be kept as short as possible. The GND side of these
capacitors should connect directly to the ground plane
of the part. These capacitors provide the AC current
to the internal power MOSFETs and their drivers. It is
important to minimize inductance from these capacitors
to the VIN pins of the LTC3371.
4. The switching power traces connecting SWA, SWB,
SWC, SWD, SWE, SWF, SWG, and SWH to the inductors
should be minimized to reduce radiated EMI and parasitic
coupling. Due to the large voltage swing of the switching
nodes, high input impedance sensitive nodes, such as the
feedback nodes, should be kept far away or shielded from
the switching nodes or poor performance could result.
5. The GND side of the switching regulator output capaci-
tors should connect directly to the thermal ground plane
of the part. Minimize the trace length from the output
capacitor to the inductor(s)/pin(s).
6. In a multiple power stage buck regulator application
the trace length of switch nodes to the inductor must
be kept equal to ensure proper operation.
7. Care should be taken to minimize capacitance on the
TEMP pin. If the TEMP voltage must drive more than
~30pF, then the pin should be isolated with a resistor
placed close to the pin of a value between 10k and 100k.
Keep in mind that any load on the isolation resistor will
create a proportional error.
Typical Applications
4 Ã 2A Quad Buck Application
2.25V TO 5.5V
22µF
1.2V
2A
2.2µH
47µF 232k
464k
VINA
VINB
SWA
SWB
FB1
VING
VINH
SWG
SWH
FB4
2.2µH
806k
649k
1.8V
2A
47µF
2.25V TO 5.5V
22µF
2.5V TO 5.5V
22µF
2.5V
2A
2.2µH
47µF 665k
309k
VINC
VINE
VIND
VINF
SWC
SWE
SWD
SWF
LTC3371
FB2
FB3
2.2µH
511k
162k
3.3V
2A
47µF
3.3V TO 5.5V
22µF
20
MICROPROCESSOR
CONTROL
EN1
VCC
EN2
EN3
EN4
RST1
PLL/MODE
RST2
C1
RST3
C2
RST4
C3
WDO
WDI
TEMP
RT
CT
402k
EXPOSED PAD
2.7V TO 5.5V
1M
10µF
MICROPROCESSOR
CONTROL
3371 TA02
For more information www.linear.com/LTC3371
3371fa
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