LTC3371 datasheet(20/26 Pages) LINER

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LTC3371

3371fb

For more information www.linear.com/LTC3371

APPLICATIONS INFORMATION

PCB Considerations

When laying out the printed circuit board, the following list

shouldbefollowedtoensureproperoperationoftheLTC3371:

1. Theexposedpadofthepackage(Pin39)shouldconnect

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. Theconnectionstotheswitchingregulatorinputsupply

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

importanttominimizeinductancefromthesecapacitors

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

shouldbeminimizedtoreduceradiatedEMIandparasitic

coupling. Due to the large voltage swing of the switching

nodes,highinputimpedancesensitivenodes,suchasthe

feedbacknodes,shouldbekeptfarawayorshieldedfrom

the switching nodes or poor performance could result.

5. The GND side of the switching regulator output capaci-

torsshouldconnectdirectlytothethermalgroundplane

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

LTC3371

EXPOSED PAD

2.2µH

VINA

VINB

SWA

SWB

FB1

VING

VINH

SWG

SWH

FB4

VINC

VIND

SWC

SWD

FB2

VINE

VINF

SWE

SWF

FB3

3371 TA02

2.2µH

806k

649k

232k

464k

22µF

2.25V TO 5.5V

1.8V

1.2V

47µF

22µF

2.25V TO 5.5V

402k

EN1

EN2

EN3

EN4

PLL/MODE

VCC

RST1

RST2

RST3

RST4

WDO

WDI

TEMP

MICROPROCESSOR

CONTROL

2.7V TO 5.5V

MICROPROCESSOR

CONTROL

10µF

2.2µH

511k

162k

665k

309k

22µF

2.5V TO 5.5V

3.3V

2.5V

47µF

22µF

3.3V TO 5.5V

4 × 2A Quad Buck Application

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