MCP19035-AAAAESLASHMF datasheet(27/44 Pages) MICROCHIP

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 2012-2013 Microchip Technology Inc.

DS22326B-page 27

MCP19035

6.0

DESIGN EXAMPLE

This example illustrates the step-by-step design proce-

dure for a 12V to 1.8V synchronous buck converter

using the MCP19035 controller. To minimize the design

effort, Microchip provides a design tool that is used to

calculate the component values. See AN1452 - “Using

the MCP19035 Synchronous Buck Converter Design

Tool”

for further details (DS01452).

The electrical parameters are detailed in Table 6-1.

6.0.1

INDUCTOR SELECTION

The inductor must be sized for a typical ripple current

that is around 30% of maximum output current. The

inductor value calculated with Equation 5-1 is 1.16 µH.

To compensate against component tolerance, choose

the next higher standard value 1.5 µH (typically 20% for

high current inductors).

The peak current in the inductor can be calculated with

Equation 5-2, its value being 17.25A. The inductor

must sustain, without saturating, this peak current. To

maintain low-conduction losses, the DC resistance of

the inductor must be as low as possible. Table 6-2

shows some suitable inductors for this application.

TABLE 6-1:

DESIGN EXAMPLE ELECTRICAL SPECIFICATION

Parameter

Test Conditions

Min

Nominal

Max

Unit

Input Voltage (VIN)

Output Voltage (VOUT)0  IOUT  15A

—

1.8

—

Line Regulation

8.0V

 VIN  14V

—

0.5

Load Regulation

 IOUT  15A

—

0.5

Output ripple (VOUT_RIPPLE)IOUT = 15A

—

Input ripple (VIN_RIPPLE)IOUT =15A

—

0.3

Output overshoot

Step from 3.75A to 11.25A

—

100

Output undershoot

Step from 11.25A to 3.75A

—

100

Output current (IOUT)0

—

Efficiency

VIN =12V, IOUT = 10A

—

TABLE 6-2:

SUITABLE INDUCTORS FROM VARIOUS VENDORS

Vendor

Part Number

Inductance

(µH)

DCR

)

ISAT

(A)

Coilcraft®

XAL1010-152MEB

1.5

1.76

36.6

Wurth Elektronik®

7443320150

1.5

2.1

TDK - EPC®

B82559A0142A013

1.4

1.5

Bourns®

SRP1270-1R5M

1.5

2.1

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