TPS62933O datasheet(29/47 Pages) TI

29 / 47 page

Equation 23. Using the design example values, IOUT_MAX = 3 A, CIN_EFF = 2 × 3.45 = 6.9 μF, and fSW = 500 kHz,

yields an input voltage ripple of 222 mV and a RMS input ripple current of 1.22 A.

OUT _ MAX

ESR _ MAX

0.25

)

(23)

where

• RESR_MAX = maximum series resistance of the input capacitor. It is approximately 1.5 mΩ of two capacitors in

paralleled.

9.2.2.10 Feedforward Capacitor CFF Selection

In some cases, a feedforward capacitor can be used across RFBT to improve the load transient response or

improve the loop phase margin. This is especially true when values of RFBT > 100 kΩ are used. Large values

of RFBT in combination with the parasitic capacitance at the FB pin can create a small signal pole that interferes

with the loop stability. A CFF helps mitigate this effect. Use lower values to determine if any advantage is gained

by the use of a CFF capacitor.

The Optimizing Transient Response of Internally Compensated DC-DC Converters with Feedforward Capacitor

Application Report is helpful when experimenting with a feedforward capacitor.

For this example design, a 10-pF capacitor C9 can be mounted to boost load transient performance.

9.2.2.11 Maximum Ambient Temperature

As with any power conversion device, the TPS62933 dissipates internal power while operating. The effect of

this power dissipation is to raise the internal temperature of the converter above ambient. The internal die

temperature (TJ) is a function of the following:

• Ambient temperature

• Power loss

• Effective thermal resistance, RθJA, of the device

• PCB combination

The maximum internal die temperature for the TPS62933 must be limited to 150°C. This establishes a limit on

the maximum device power dissipation and, therefore, the load current. Equation 24 shows the relationships

between the important parameters. It is easy to see that larger ambient temperatures (TA) and larger values

of RθJA reduce the maximum available output current. The converter efficiency can be estimated by using

the curves provided in this data sheet. Note that these curves include the power loss in the inductor. If the

desired operating conditions cannot be found in one of the curves, then interpolation can be used to estimate

the efficiency. Alternatively, the EVM can be adjusted to match the desired application requirements and the

efficiency can be measured directly. The correct value of RθJA is more difficult to estimate. As stated in the

Semiconductor and IC Package Thermal Metrics Application Report, the value of RθJA given in the Thermal

Information table is not valid for design purposes and must not be used to estimate the thermal performance of

the application. The values reported in that table were measured under a specific set of conditions that are rarely

obtained in an actual application. The data given for RθJC(bott) and ΨJT can be useful when determining thermal

performance. See the Semiconductor and IC Package Thermal Metrics Application Report for more information

and the resources given at the end of this section.

OUT _ MAX

OUT

(T -T )

(24)

where

• ŋ = efficiency

The effective RθJA is a critical parameter and depends on many factors such as the following:

• Power dissipation

www.ti.com

TPS62933

SLUSEA4A – JUNE 2021 – REVISED DECEMBER 2021

Submit Document Feedback

Product Folder Links: TPS62933

TPS62933O Datasheet(PDF) 29 Page - Texas Instruments

TPS62933O Datasheet(HTML) 29 Page - Texas Instruments

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 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Datasheet Download

Link URL