SC4602A データシートの表示（PDF） - Semtech Corporation

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SC4602A

High Efficiency Synchronous, Step Down Controller

Semtech Corporation 

SC4602A/B

POWER MANAGEMENT

Applications Information (Cont.)

Layout Guideline

In order to achieve optimal electrical, thermal and noise

performance for high frequency converters, special at-

tention must be paid to the PCB layouts. The goal of lay-

out optimization is to identify the high di/dt loops and

minimize them. The following guideline should be used to

ensure proper functions of the converters.

1. A ground plane is recommended to minimize noises

and copper losses, and maximize heat dissipation.

2. Start the PCB layout by placing the power compo-

nents first. Arrange the power circuit to achieve a

clean power flow route. Put all the connections on

one side of the PCB with wide copper filled areas if

possible.

3. The Vcc bypass capacitor should be placed next to

the Vcc and GND pins.

4. The trace connecting the feedback resistors to the

output should be short, direct and far away from the

noise sources such as the phase node and switching

components.

5. Minimize the traces between PDRV/NDRV and the

gates of the MOSFETs to reduce their impedance to

drive the MOSFETs.

6. Minimize the loop including input capacitors, top/bot-

tom MOSFETs. This loop passes high di/dt current.

Make sure the trace width is wide enough to reduce

copper losses in this loop.

7. The PHASE connection to P-MOSFET for current sens-

ing must use Kelvin connection.

8. Maximize the trace width of the loop connecting the

inductor, bottom MOSFET and the output capacitors.

9. Connect the ground of the feedback divider and the

compensation components directly to the GND pin

of the SC4602A/B by using a separate ground trace.

Then connect this pin to the ground of the output

capacitor as close as possible.

A Design Example: 3.3V to1.5V @6A application with SC4602B (NH020 footprint)

R15

1

C3

4.7u

R2

3.32K

C1

470p

C2

6.8n

R1

5.11k

U1

1 VCC

PDRV 8

2 SY NC/SLEEP NDRV 7

3 COMP

GND 6

4 VSENSE

PHASE 5

SC4602B

R11

100

ON / OF F

M1

R6

1.0

M2

R5

1.0

Vin = 3.3V

C10

C11

C12

C13

22u

22u

22u

22u

L1

1.6u

C7

C4

150u

22u

GND

1

2

3

4

5

ON/OFF 6

J1

Vo = 1.5V/6A

C9

3.3n

R8

169

R7

4.64k

R9

5.36k

1

2

3

4

5

J2

R10

TRIM

100

Figure 5. Schematic for 3.3V/1.5V@6A with SC4602B application

 2006 Semtech Corp.

14

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