ACT2861 datasheet(46/97 Pages) QORVO

46 / 97 page

Data Sheet Rev. F, April 2022 | Subject to change without notice

46 of 97

www.qorvo.com

ACT2861

30V Buck-Boost Charger with Integrated MOSFETs and OTG

or similar dielectrics is not recommended. Input capaci-

tor placement is critical for proper operation. The input

capacitor must be placed as close to the IC as possible.

The traces from VBAT to the capacitor and from the ca-

pacitor to PGND should as short and wide as possible.

OTG – Output Capacitor Selection

Note that the OTG COUT capacitors are also the charg-

ing input capacitors. They are connected to VIN. The

output capacitance must be a combination of ceramic

and bulk capacitance.

Table 11 gives the required capacitor values for stability.

Note that the table has two output capacitor options:

Standard Capacitance and Minimum Capacitance.

The Standard Capacitance design requires more over-

all capacitance, but places no restriction on the bulk

capacitor ESR. The Minimum Capacitance design re-

sults in an overall smaller design, but places restrictions

on the ESR. The capacitor values can be increased

without limit.

Note that the Ceramic and Bulk capacitor values are

recommended “Capacitor Values”. When choosing the

ceramic capacitors, use X5R or X7R dielectrics and be

sure to consider the capacitor’s tolerance and DC bias

effects. Use of Y5U, Z5U, or similar dielectrics is not

recommended. The 22uF capacitor must have at least

9uF of effective capacitance for stability. The 47uF ca-

pacitor must have 19uF of capacitance. The bulk capac-

itors do not have DC bias effects.

Output ceramic capacitor placement is critical for proper

operation. The output capacitor must be placed as close

to the IC as possible. The traces from VIN to the capac-

itor and from the capacitor to PGND should as short and

wide as possible. The bulk capacitor should be placed

to the left of the current sense resistor. Refer to the Lay-

out Guidelines selection and to the EVK layout for

additional details.

OTG - Inductor Selection

The buck-boost regulator utilizes current-mode control

and a proprietary compensation scheme to simultane-

ously compensate the buck, buck-boost, and boost

modes of operation. The ACT2861 compensation re-

quires a fixed inductor value that is matched to the

switching frequency. Table 9 gives the required inductor

value. Choose an inductor with a low DC-resistance,

and avoid inductor saturation by choosing inductors with

DC ratings that exceed the maximum output current by

at least 30%. The inductor value must be within +30%

to -30% across all operating conditions.

OTG - Compensation

The ACT2861 operates in three switching modes: buck,

buck-boost, and boost mode depending on the input

and output voltage ratios. The IC contains a proprietary

compensation scheme to simultaneously compensate

all three switching modes. The compensation values

are directly tied to the switching frequency and required

inductor value. Table 9 provides the required compen-

sation values. Figure 16 shows the OTG compensation

components.

Table 11: OTG Inductor and Compensation

Standard Capacitance Design

Minimum Capacitance Design

Switching

Frequency

Inductor

Min / Typ / Max

(uH)

CICOMP1

(nF)

CICOMP2

(nF)

RICOMP

Ω)

Ceramic

Capacitor

(uF)

Bulk

Capacitor

(uF)

Bulk

Capacitor

ESR

Ω)

Ceramic

Capacitor

(uF)

Bulk

Capacitor

(uF)

Bulk

Capacitor

ESR

Ω)

125Khz

29 / 42 / 55

8.2

20.0

1000

N/A

470

30 - 100

250Khz

15 / 22 / 29

3.9

20.0

470

N/A

220

50 - 200

500KHz

7 / 10 / 13

2.2

20.0

220

N/A

100

50 - 200

1MHZ

4 / 5.6 / 7.28

1.0

20.0

100

N/A

100

50 - 200

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