L1 =

5V x (75V ± 5V)

0.5A x 300 kHz x 75V

= 31 PH

(

)

(

)

(

)

OUT

OUT

IN max

RIPPLE

S

IN max

V

V

V

L1

I

F

V

´

-

=

´

´

0 mA

1/Fs

9

3

T

12

1

580

10

300

10

R

135

10

-

-

æ

ö

æ

ö

-

´

ç

÷

ç

÷

´

è

ø

è

ø

=

´

LM5576, LM5576-Q1

SNVS447I – JANUARY 2007 – REVISED APRIL 2013

www.ti.com

Thermal Protection

Internal Thermal Shutdown circuitry is provided to protect the integrated circuit in the event the maximum junction

temperature is exceeded. When activated, typically at 165°C, the controller is forced into a low power reset state,

disabling the output driver and the bias regulator. This feature is provided to prevent catastrophic failures from

accidental device overheating.

Application Information

EXTERNAL COMPONENTS

The procedure for calculating the external components is illustrated with the following design example. The Bill of

Materials for this design is listed in Table 1. The circuit shown in Figure 9 is configured for the following

specifications:

•

•

•

Fs = 300kHz

•

Minimum load current (for CCM) = 250mA

•

Maximum load current = 3A

losses. Operation at 300kHz was selected for this example as a reasonable compromise for both small size and

(7)

The nearest standard value of 21k

L1

The inductor value is determined based on the operating frequency, load current, ripple current, and the

Figure 16. Inductor Current Waveform

than twice the minimum load current, or 0.5Ap-p. Using this value of ripple current, the value of inductor (L1) is

calculated using the following:

(8)

(9)

14

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