TPS62870 datasheet(18/66 Pages) TI2

18 / 66 page

During PWM-DCM operation, the device switches at a constant frequency and the inductor current is

discontinuous (see Figure 7-3). In this mode, the device controls the peak inductor current to maintain the

selected switching frequency while still being able to regulate the output.

Use Equation 2 to calculate the output current threshold at which the device enters PWM-DCM.

IOUTCCM−DCM = VIN–VOUT2LtON

(2)

with tON according Equation 1.

t1/f

SWt

Time

Figure 7-3. Discontinuous Conduction Mode (PWM-DCM) Current Waveform

During PFM-DCM operation, the device keeps the peak inductor current constant (at a level corresponding to the

minimum on time of the converter) and skips pulses to regulate the output (see Figure 7-4). The switching pulses

that occur during PFM-DCM operation are synchronized to the internal clock.

t1/fSWt

Time

t1/fSWt

Skipped Pulses

Minimum on-time

Figure 7-4. Discontinuous Conduction Mode (PFM-DCM) Current Waveform

Use Equation 3 to calculate the output current threshold at which the device changes from PWM-DCM to

PFM-DCM:

IOUTPFM−DCM =VIN×tON_min_PFM

2 × 1−VOUTVINL

(3)

with tON_min_PFM being the minimum on time in PFM-DCM of approximately 20ns.

Figure 7-5 shows how this threshold typically varies with VIN and VOUT for a switching frequency of 2.25MHz.

TPS62870, TPS62871, TPS62872, TPS62873

SLVSGC5E – JANUARY 2023 – REVISED OCTOBER 2025

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TPS62870 Datasheet(PDF) 18 Page - Texas Instruments