TPS62870 datasheet(47/66 Pages) TI2

47 / 66 page

9.2.2.3 Selecting the Compensation Resistor

Use Equation 13 to calculate the recommended value of compensation resistor, RZ:

RZ= 1gm π× ∆IOUT+ILPP2 × LNɸ

4×τ×∆VOUT – 1 1+ TOLIND2+TOLτ2

(13)

RZ= 11.5×10–3 π×7.5+2.3422 ×110×10–91

4×12.5×10–6×17.25×10–3 – 1 1+ 20%2+30%2 =2.244kΩ

(14)

Rounding up, the closest standard value from the E24 series is 2.4kΩ.

9.2.2.4 Selecting the Output Capacitors

In practice, the total output capacitance is typically comprised of a combination of different capacitors, in which

larger capacitors provide the load current at lower frequencies and smaller capacitors provide the load current

at higher frequencies. The value, type, and location of the output capacitors are critical for correct operation. TI

recommends low-ESR multilayer ceramic capacitors with an X7R dielectric (or similar) for best performance.

The TPS6287x devices feature a butterfly layout with two GND pins on opposite sides of the package. This

allows the output capacitors to be placed symmetrically on the PCB such that the electromagnetic fields

generated cancel each other out, thereby reducing EMI.

The transient response of the converter is limited by one of two criteria:

• The slew rate of the current through the inductor, in which case, the feedback loop of the converter saturates.

• The maximum allowed ratio of converter bandwidth to switching frequency, in which the converter remains

in regulation (that is, the loop does not saturate). TI recommends a minimum ratio of four for typical

applications.

Which of the above criteria applies in any given application depends on the operating conditions and component

values used. Therefore, TI recommends that the user calculate the output capacitance for both cases, and select

the higher of the two values.

If the converter remains in regulation, the minimum output required capacitance is given by:

COUTmin reg = τ× 1+gm×RZ

2×π× LNɸ×fSW4 1+ TOLτ2+TOLIND2+TOLfSW2

(15)

COUTmin reg = 12.5×10–6× 1+1.5×10–3×2.4×103

2×π×110×10–91×2.25×1064 1+ 30%2+20%2+10%2 =203.2μF (16)

If the converter loop saturates, the minimum output capacitance is given by:

COUTmin sat = 1∆VOUT LNɸ× ∆IOUT+ILPP2 2

2×VOUT – ∆IOUT×tt2 1+TOLIND

(17)

COUTmin sat = 1

17.25×10–3 110×10

–91× 7.5+2.34222

2×0.75 – 7.5×1×10–6

2 1+20% =122.7μF (18)

In this case, choose COUT(min) = 203µF as the larger of the two values for the output capacitance.

www.ti.com

TPS62870, TPS62871, TPS62872, TPS62873

SLVSGC5E – JANUARY 2023 – REVISED OCTOBER 2025

Submit Document Feedback

Product Folder Links: TPS62870 TPS62871 TPS62872 TPS62873

TPS62870 Datasheet(PDF) 47 Page - Texas Instruments

TPS62870 Datasheet(HTML) 47 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 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

Datasheet Download

Link URL