LP2983 datasheet(16/25 Pages) TI1

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LP2983

SNVS170D – OCTOBER 2001 – REVISED APRIL 2016

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8.2.2.4 Estimating Junction Temperature

The EIA/JEDEC standard recommends the use of psi (

Ψ) thermal characteristics to estimate the junction

temperatures of surface mount devices on a typical PCB board application. These characteristics are not true

thermal resistance values, but rather package specific thermal characteristics that offer practical and relative

means of estimating junction temperatures. These psi metrics are determined to be significantly independent of

copper-spreading area. The key thermal characteristics (

ΨJT and ΨJB) are given in Thermal Information and are

used in accordance with Equation 4 or Equation 5.

TJ(MAX) = TTOP + (ΨJT × PD(MAX))

where

•

PD(MAX) is explained in Equation 3

•

TTOP is the temperature measured at the center-top of the device package.

(4)

TJ(MAX) = TBOARD + (ΨJB × PD(MAX))

where

•

PD(MAX) is explained in Equation 3.

•

TBOARD is the PCB surface temperature measured 1-mm from the device package and centered on the

package edge.

(5)

For more information about the thermal characteristics

ΨJT and ΨJB, see Semiconductor and IC Package

Thermal Metrics (SPRA953); for more information about measuring TTOP and TBOARD, see Using New Thermal

Metrics (SBVA025); and for more information about the EIA/JEDEC JESD51 PCB used for validating RθJA, see

Thermal Characteristics of Linear and Logic Packages Using JEDEC PCB Designs (SZZA017). These

application notes are available at www.ti.com.

8.2.3 Application Curves

Unless otherwise specified, CIN = 1 μF, COUT = 2.2 μF, VIN = VOUT(NOM) + 1, TA = 25°C, ON/OFF pin is tied to VIN..

Figure 25. Line Transient Response

Figure 26. Load Transient Response

9 Power Supply Recommendations

The LP2983 is designed to operate from an input voltage supply range between 2.2 V and 16 V. The input

voltage range provides adequate headroom for the device to have a regulated output. This input supply must be

well regulated. If the input supply is noisy, additional input capacitors with low ESR can help improve the output

noise and transient performance.

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