ACT2861 datasheet(36/97 Pages) QORVO

36 / 97 page

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

36 of 97

www.qorvo.com

ACT2861

30V Buck-Boost Charger with Integrated MOSFETs and OTG

Table 4: Charge Current Component Selection

Switching Frequency = 125kHz

IOLIM

(A)

RCS

(mΩ)

ROLIM

(kΩ)

RCS_COMP

(kΩ)

CCS_COMP

(nF)

330

1.5

330

Switching Frequency = 250kHz, 500kHz, 1MHz

IOLIM

(A)

RCS

(mΩ)

ROLIM

(kΩ)

RCS_COMP

(kΩ)

CCS_COMP

(nF)

1.5

100

To eliminate noise in the current measurement circuit,

the current sense voltage must be filtered. The recom-

mended values are ROSRP = ROSRN = 30.1ohm and

COSR = 100nF. These values can be scaled up or down,

but ROSRP must be between 20ohm and 50ohm, and

the resulting filter cutoff frequency must be between

20kHz and 30kHz.

The actual charge current can be measured with the

OLIM pin. The OLIM voltage is directly proportional to

the charging current. The following equation calculates

the charging current.

��=��2��

Where IOLIM is the hardware programmed 100%

charging current in amps and VOLIM is the voltage

measured at the OLIM pin.

Note that the output current in charge mode becomes

the input current in OTG mode.

Charging – Dead Battery, Short Circuit, and

Precharge Currents

The charger operates at reduced currents when the bat-

tery voltage is low. This protects the battery chemistry

and prepares it for fast charging. When in the

SCOND_DB mode, the charger supplies a fixed 10mA

of charge current.

When in the SCOND mode, the charger supplies the

“short battery” current, ISHRT. ISHRT is a fixed percent-

age

ICHG

which

set

the

I2C

bits

VBAT_SHORT_CURRENT in register 0x0Bh.

When in the PCOND mode (precharge), the charger

supplies the “precharge” current, IPRECHG. IPRECHG

is a fixed percentage of ICHG which is set by the I2C

bits IPRECHG in register 0x19h. IPRECHG can set the

precharge current from 5% to 20% of the ICHG.

Charging - Maximum Input Current Limit

In Charge mode, the IC features an input current limit

circuit to meet maximum input current limitations for

USB sources and to avoid over loading weak input volt-

age sources. Figure 12 shows that the input current lim-

iting circuitry is identical to the charge current setting

circuitry. When the input current reaches current limit,

the ACT2861 control circuitry starts regulating the max-

imum input current. When in charge mode, this effec-

tively lowers the charge current to maintain the maxi-

mum programmed input current. The maximum allowa-

ble input current is 5A. The actual input current limit,

IIN_LIM can be scaled from 1% to 100% of IILIM in 1%

steps. The following equation defines the final input cur-

rent limit.

��_��=��∗��[6:0]

Where IILIM is the hardware programmed current limit

and INLIM[6:0] is the scaling factor. INLIM[6:0] is the

decimal equivalent value in this register. For example, if

IILIM, is programmed to 5A and INLIM[6:0] = 0111100b

(60% decimal), the final charge current = 5A * 0.60 = 3A.

Note that INLIM[6:0] is a 7 bit register and can be pro-

grammed between 0x00h and 0x7Fh (0% and 127%). If

a value of 0x00h is written to the register, the register

retains 0x00h, but the IC sets the input current to 1%. If

a value above 0x64h (100%) is written to the register,

the IC retains the written value, but sets the input cur-

rent to 100%.

Input current limit can be set by the ILIM pin and

IINLIM[6:0] registers.

ACT2861 Datasheet(PDF) 36 Page - Qorvo, Inc

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