EC9301A datasheet(13/16 Pages) E-CMOS

13 / 16 page

E-CMOS Corp. (www.ecmos.com.tw)

Page 13 of 16

5J22N Rev. F001

3A 150KHz PWM Buck DC/DC Converter

EC9301A

Function Description(Cont.)

noise of this circuit and improves efficiency. A ground

plane is recommended to connect input capacitor, output

capacitor, and GND pin of the EC9301A.

In the EC9301A buck regulator circuit, the two major

power dissipating components are the EC9301A and

output inductor. The total power dissipation of converter

circuit can be measured by input power minus output

power.

Ptotal _loss = V IN × IIN

– V O × IO

The power dissipation of inductor can be approximately

calculated by output current and DCR of inductor.

Pinductor _loss= IO 2 × Rinductor × 1.1

The junction to ambient temperature can be got from

power dissipation in the EC9301A and thermal impedance

from junction to ambient.

T (jun-amb) =(Ptotalloss

–Pinductorloss)× ΘJA

The maximum junction temperature of EC9301A is 145°C,

which limits the maximum load current capability. Please

see the thermal de-rating curves for the maximum load

current of the EC9301A under different ambient

temperatures.

The thermal performance of the EC9301A is trongly

affected by the PCB layout. Extra care should be taken

by users during the design process to nsure that the IC

will operate under the recommended environmental

conditions.

Several layout tips are listed below for the best electric

and thermal performance.

1. Do not use thermal relief connection to the VIN and

the GND pin. Pour a maximized copper area to the GND

pin and the VIN pin to help thermal dissipation.

2. Input capacitor should be connected to the VIN pin

and the GND pin as close as possible.

3. Make the current trace from VOUT pins to L to the

GND as short as possible.

4. Pour copper plane on all unused board area and

connect it to stable DC nodes, like VIN, GND, or VOUT.

5. Keep sensitive signal traces such as trace connecting

FB pin away from the VOUT pins.

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