MP2110 – 3A SYNCHRONOUS BUCK CONVERTER WITH INPUT CURRENT LIMIT

MP2110 Rev. 1.11

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13

9/26/2014

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equivalent series resistance (ESR) value of the

output capacitor.

Using ceramic capacitors, the impedance at the

switching frequency is dominated by the

capacitance. The output voltage ripple is mainly

caused by the capacitance. For simplification,

the output voltage ripple can be estimated by:

OUT

OUT

OUT

2

S1

IN

VV

ΔV1

8f

L

C3

V

⎛⎞

=× −

⎜⎟

×× ×

⎝⎠

In the case of tantalum or electrolytic capacitors,

the ESR dominates the impedance at the

switching frequency. For simplification, the

output ripple can be approximated to:

OUT

OUT

OUT

ESR

IN

S1

VV

ΔV1

R

fL

V

⎛⎞

=× −

×

⎜⎟

×

⎝⎠

The characteristics of the output capacitor also

affect the stability of the regulation system.

PC Board Layout

PCB layout is very important to achieve stable

operation. For best results, follow these

guidelines and use Figure 2 as reference:

1) Use large ground plane directly connect to

PGND pin. Add vias near the PGND pin if

bottom layer is ground plane.

2) Place the ceramic input capacitor close to

SYSIN/REGIN and PGND pins. Keep the

connection

of

input

capacitor

and

SYSIN/REGIN pin as short and wide as

possible.

3) Route SW away from sensitive analog

areas such as FB, OUT pins. It’s not

recommended to route SW trace under

chip’s bottom side.

4) Place the feedback resistors close to chip

to ensure the trace which connects to FB

pin as short as possible.

C2

C3

VOUT

VOUT

Top Layer

Bottom Layer

GND

SYSIN

GND

GND

REGIN

C2A

R6

R1

R2

C4

R4

C1

C1A

C3

C3A

L1

Figure 2: PCB Layout

Design Example

Below is a design example following the

application guidelines for the specifications:

Table 4—Design Example

5V

3.6V

3A

The detailed application schematic is shown in

Figure 3. The typical performance and circuit

waveforms have been shown in the Typical

Performance Characteristics section. For more

device applications, please refer to the related

Evaluation Board Datasheet.