TC2575 datasheet(16/25 Pages) TELCOM

16 / 25 page

TC2575

1.0A Step-Down Switching Regulator

TC2575-1 3/13/00

Thermal Analysis and Design

The following procedure must be performed to deter-

mine whether or not a heatsink will be required. First

determine:

1. PD (max) – maximum regulator power dissipation in the

application.

2. TA (max) – maximum ambient temperature in the

application.

3. TJ (max) – maximum allowed junction temperature

(125

°C for the TC2575). For a conservative design, the

maximum junction temperature should not exceed 110

°C

to assure safe operation. For every additional 10

°C tem-

perature rise that the junction must withstand, the estimated

operating lifetime of the component is halved.

ΘJC – package thermal resistance junction–case.

ΘJA – package thermal resistance junction–

ambient.

(Refer to Absolute Maximum Ratings on this data sheet

ΘJC and ΘJA values).

The following formula is to calculate the approximate

total power dissipated by the TC2575:

PD = (VIN x IQ ) + d x ILOAD x VSAT

where d is the duty cycle and for buck converter

d =

tON

VOUT

VIN

IQ (quiescent current) and VSAT can be found in the

TC2575 data sheet,

VIN is minimum input voltage applied,

VOUT is the regulator output voltage,

ILOAD is the load current.

The dynamic switching losses during turn–on and turn–

off can be neglected if a proper type catch diode is used.

Packages (Free–Standing)

For a free–standing application when no heatsink is

used, the junction temperature can be determined by the

following expression:

TJ = (ΘJA ) (PD ) + TA

where (

ΘJA )(PD ) represents the junction temperature

rise caused by the dissipated power and TA is the maxi-

mum ambient temperature.

Some Aspects That can Influence

Thermal Design

It should be noted that the package thermal resistance

and the junction temperature rise numbers are all approxi-

mate, and there are many factors that will affect these

numbers, such as PC board size, shape, thickness, physical

position, location, board temperature, as well as whether the

surrounding air is moving or still.

Other factors are trace width, total printed circuit copper

area, copper thickness, single– or double–sided, multilayer

board, the amount of solder on the board or even color of the

traces.

The size, quantity and spacing of other components on

the board can also influence its effectiveness to dissipate

the heat.

Figure 8. Inverting Buck-Boost Regulator Using the TC2575 (12V)

Develops –12V @ 0.35A

1N5819

100

µH

Output

GND

Feedback

12 to 25V

Unregulated

DC Input

ON/OFF

+VIN

–12V @ 0.35A

Regulated

Output

TC2575

(12V)

COUT

1800

µF/

16V

CIN

100

µF

/50V

TC2575 数据表(PDF) 16 Page - TelCom Semiconductor, Inc

TC2575 数据表(HTML) 16 Page - TelCom Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

数据表下载