Load

Transient

Line

Transient

VIN

VOUT

NOM

~90%

~85%

VERROR

Power-Down

~2.25V

~1.55V

~1.25V

~1.25V

~2.50V

~2.50V

Power-Up

LP38512

SNOSAU7F – NOVEMBER 2007 – REVISED APRIL 2013

www.ti.com

Figure 24. ERROR Flag Operation, biased from VIN

POWER DISSIPATION/HEATSINKING

A heatsink may be required depending on the maximum power dissipation (PD(MAX)), maximum ambient

temperature (TA(MAX)) of the application, and the thermal resistance (θJA) of the package. Under all possible

conditions, the junction temperature (TJ) must be within the range specified in the Operating Ratings. The total

power dissipation of the device is given by:

PD = ( (VIN−VOUT) x IOUT) + (VIN x IGND)

where IGND is the operating ground current of the device (specified under Electrical Characteristics).

The maximum allowable junction temperature rise (

ΔTJ) depends on the maximum expected ambient

temperature (TA(MAX)) of the application, and the maximum allowable junction temperature (TJ(MAX)):

ΔTJ = TJ(MAX)− TA(MAX)

The maximum allowable value for junction to ambient Thermal Resistance,

θJA, can be calculated using the

formula:

θJA = ΔTJ / PD(MAX)

HEATSINKING DDPAK/TO-263 PACKAGE

The DDPAK/TO-263 and the PFM packages use the copper plane on the PCB as a heatsink. The tab, or DAP,

of these packages are soldered to the copper plane for heat sinking. Figure 25 shows a curve for the

θJA of

DDPAK/TO-263 package for different copper area sizes, using a typical PCB with 1 ounce copper and no solder

mask over the copper area for heat sinking.

12

Submit Documentation Feedback

Copyright © 2007–2013, Texas Instruments Incorporated

Product Folder Links: LP38512