LMZ14201HTZXSLASHNOPB datasheet(23/31 Pages) TI1

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1.2

1.5

OUTPUT CURRENT (A)

VIN = 15V

VIN = 24V

VIN = 30V

VIN = 36V

VIN = 42V

Top View

VIN

COUT

VOUT

RENT

RON

CSS

GND

Thermal Vias

CIN

GND

RENB

CFF

RFBT

RFBB

GND Plane

EPAD

LMZ14201H

www.ti.com

SNVS690H – JANUARY 2011 – REVISED OCTOBER 2015

Layout Example (continued)

Figure 50. PCB Layout Guide

10.3 Power Dissipation and Board Thermal Requirements

For a design case of VIN = 24 V, VOUT = 12 V, IOUT = 1 A, TA (MAX) = 85°C , and TJUNCTION = 125°C, the device

must see a maximum junction-to-ambient thermal resistance of:

RθJA-MAX < (TJ-MAX – TA(MAX)) / PD

(20)

This RθJA-MAX will ensure that the junction temperature of the regulator does not exceed TJ-MAX in the particular

application ambient temperature.

To calculate the required RθJA-MAX we need to get an estimate for the power losses in the IC. Figure 51 is taken

from the Typical Characteristics section and shows the power dissipation of the LMZ14201H for VOUT = 12 V at

85°C TA.

Figure 51. Power Dissipation VOUT = 12 V, TA = 85°C

Using the 85°C TA power dissipation data as a conservative starting point, the power dissipation PD for VIN = 24

V and VOUT = 12 V is estimated to be 0.75 W. The necessary RθJA-MAX can now be calculated.

RθJA-MAX < (125°C - 85°C) / 0.75 W

(21)

RθJA-MAX < 53.3°C/W

(22)

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