MCP1602 datasheet(15/26 Pages) MICROCHIP

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DS22061A-page 15

MCP1602

Table 5-1 contains the recommend range for the output

capacitor value.

5.6

Inductor Selection

For most applications an inductor value of 4.7 µH is

recommended to achieve a good balance between

converter load transient response and minimized

noise. There are many different magnetic core

materials and package options to select from. That

decision is based on size, cost, and acceptable

radiated energy levels. Toroid and shielded ferrite pot

cores will have low radiated energy, but tend to be

larger and higher in cost.

The value of inductance is selected to achieve a

desired amount of ripple current. It is reasonable to

assume a ripple current that is 20% of the maximum

load current. The larger the amount of ripple current

allowed, the larger the output capacitor value becomes

to meet ripple voltage specifications. The inductor

ripple

current

can

calculated

according

Equation 5-4.

EQUATION 5-4:

When considering inductor ratings, the maximum DC

current rating of the inductor should be at least equal to

the maximum load current, plus one half the peak-to-

peak inductor ripple current (1/2 *

ΔI

L). The inductor DC

resistance adds to the total converter power loss. An

inductor with a low DC resistance allows for higher

converter efficiency.

5.7

Thermal Calculations

The MCP1602 is available in two different packages

(MSOP and 3x3 DFN). By calculating the power

dissipation

and

applying

the

package

thermal

resistance, (

JA),

the

junction

temperature

estimated.

The

maximum

continuous

junction

temperature rating for the MCP1602 is +125oC.

To quickly estimate the internal power dissipation for

the switching buck regulator, an empirical calculation

using measured efficiency can be used. Given the

measured efficiency, the internal power dissipation is

estimated by:

EQUATION 5-5:

The difference between the first term, input power

dissipation, and the second term, power delivered, is

the internal power dissipation. This is an estimate

assuming that most of the power lost is internal to the

MCP1602. There is some percentage of power lost in

the buck inductor, with very little loss in the input and

output capacitors.

TABLE 5-1:

CAPACITOR VALUE RANGE

CIN

COUT

Minimum

4.7 µF

Maximum

—

22 µF

TABLE 5-2:

MCP1602 RECOMMENDED

INDUCTORS

Part

Number

Value

(µH)

DCR

(max)

ISAT

(A)

Size

WxLxH (mm)

Coiltronics®

SD10

3.3

0.108

1.31

5.2x5.2x1.0

SD10

4.7

0.154

1.08

5.2x5.2x1.0

SD10

6.2

0.218

0.92

5.2x5.2x1.0

SD12

3.3

0.104

1.42

5.2x5.2x1.2

SD12

4.7

0.118

1.29

5.2x5.2x1.2

SD12

6.2

0.170

1.08

5.2x5.2x1.2

ΔI

OUT

-------------------

OUT

-------------

–

⎝⎠

⎛⎞

Where:

FSW

Switching Frequency

Wurth Elektronik®

WE-TPC

Type S

3.6

0.085

1.10

3.8x3.8x1.65

WE-TPC

Type S

4.7

0.105

0.90

3.8x3.8x1.65

WE-TPC

Type S

6.8

0.156

0.75

3.8x3.8x1.65

WE-TPC

Type M

3.3

0.065

1.80

4.8x4.8x1.8

WE-TPC

Type M

4.7

0.082

1.65

4.8x4.8x1.8

WE-TPC

Type M

6.8

0.100

1.25

4.8x4.8x1.8

TABLE 5-2:

MCP1602 RECOMMENDED

INDUCTORS (CONTINUED)

Part

Number

Value

(µH)

DCR

(max)

ISAT

(A)

Size

WxLxH (mm)

OUT

Efficiency

-------------------------------

⎝⎠

⎛⎞

OUT

()

–

Dis

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