TPS7A1106PDRVR datasheet(21/37 Pages) TI1

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Rated Output

Current

Output Current Limited

by Dropout

Output Current Limited

by Thermals

Limited by

Minimum VIN

Limited by

Maximum VIN

VIN ± VOUT (V)

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SBVS316 – SEPTEMBER 2018

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Application Information (continued)

8.1.8 Estimating Junction Temperature

The JEDEC standard now recommends the use of psi (Ψ) thermal metrics to estimate the junction temperatures

of the LDO when in-circuit on a typical PCB board application. These metrics are not strictly speaking thermal

resistances, but rather offer practical and relative means of estimating junction temperatures. These psi metrics

are determined to be significantly independent of the copper-spreading area. The key thermal metrics (ΨJT and

ΨJB) are used in accordance with Equation 6 and are given in the Electrical Characteristics table.

ΨJT : TJ = TT + ΨJT × PD and ΨJB : TJ = TB + ΨJB × PD

where:

•

PD is the power dissipated as explained in Equation 3

•

TT is the temperature at the center-top of the device package

•

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

edge

(6)

8.1.9 Recommended Area for Continuous Operation

The operational area of an LDO is limited by the dropout voltage, output current, junction temperature, and input

voltage. The recommended area for continuous operation for a linear regulator is shown in Figure 36 and can be

separated into the following regions:

•

Dropout voltage limits the minimum differential voltage between the input and the output (VIN – VOUT) at a

given output current level; see the Dropout Voltage section for more details.

•

The rated output current limits the maximum recommended output current level. Exceeding this rating causes

the device to fall out of specification.

•

The rated junction temperature limits the maximum junction temperature of the device. Exceeding this rating

causes the device to fall out of specification and reduces long-term reliability.

–

Equation 5 provides the shape of the slope. The slope is nonlinear because the maximum rated junction

temperature of the LDO is controlled by the power dissipation across the LDO, thus when VIN – VOUT

increases the output current must decrease.

•

The rated input voltage range governs both the minimum and maximum of VIN – VOUT.

Figure 36. Continuous Operation Diagram With Description of Regions

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