ACT2861 datasheet(37/97 Pages) QORVO

37 / 97 page

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

37 of 97

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ACT2861

30V Buck-Boost Charger with Integrated MOSFETs and OTG

From Input

Supply

RCS_IN

RILIM

RISRP

RISRN

CISR

ISRN

ISRP

VIN

ILIM

RCS_COMP

CCS_COMP

Figure 12: Input Current Circuitry

The current sense resistor and ILIM resistor set the IILIM

current.

��= 1000��2��

��∗��_��

Where RILIM is the resistor from the ILIM pin to AGND

and RCS_IN is the current sense resistor value in ohms.

The term 1000V^2/A is a constant with the units

volts^2/Ampere.

The current sense resistor, RCS_IN, has the same limita-

tions as RCS_OUT. At lower charging currents, additional

RC compensation must be placed in parallel with ROLIM.

Table 4 is also valid for the input current limit circuitry.

The input current limit circuitry, RISRP = RISRN = 30.1ohm

and CISR also have the same input filter requirements as

the charge circuitry.

If the system operates in input current limit mode, the

INPUT_IINLIM_STATUS bit in register 0x03h goes high.

While the input current limit is active, both the Low Bat-

tery Safety Timer and Fast Charge Safety Timer run at

a half speed to increase the overall safety timer timeout.

The actual input current can also be externally meas-

ured with the ILIM pin. The ILIM voltage is directly pro-

portional to the charging current. The following equation

calculates the actual input current.

��=��2��

Where IILIM is the hardware programmed input current

limit in amps and VILIM is the voltage measured at the

ILIM pin.

Note that the input current in charge mode becomes the

output current in OTG mode.

Charging – Minimum Input Voltage Limit

The input voltage limit feature is used to prevent the

charger from overloading USB or weak input power

sources. If the input voltage drops due to an overloaded

input source, the ACT2861 starts regulating the mini-

mum programmed input voltage to prevent the voltage

from dropping farther. When in charge mode, this effec-

tively lowers the charge current to maintain a minimum

input voltage.

The minimum input voltage threshold is programmable

between 4V and 16.7V in 100mV steps via I2C bits VIN-

LIM[6:0] in register 0x16h. The following equation sets

the minimum input voltage threshold.

��=4.0��+0.1��∗��[6:0]

Where VINLIM[6:0] is the decimal equivalent of the

value in this register. For example, to prevent a 12V in-

put source from dropping below 9V, VINLIM[6:0] =

0110010b (50 decimal), the minimum input voltage =

4.0V + 0.1V * 50 = 9.0V.

If system is in input voltage limit, the INPUT_VIN-

LIM_STATUS bit in register 0x03h goes high.

While the input voltage limit is active, both the Low Bat-

tery Safety Timer and Fast Charge Safety Timer run at

a half speed to increase the overall safety timer timeout.

Battery Thermal Control

The ACT2861 TH pin can be used to monitor the battery

temperature. An NTC resistor connected between TH

and AGND provides temperature information. Battery

temperature monitoring is valid in both Charge mode

and OTG mode. If the battery temperature is outside the

programmed upper and lower thresholds, the charger

reports a fault and stops charging.

The ACT2861 provides two temperature monitoring al-

gorithms. The first is the comprehensive industry stand-

ard JEITA compliance. The second is a simple I2C reg-

ister based high and low temperature threshold. To en-

able either method, I2C bit DIS_TH in register 0x01h

MUST be set to 0. If this bit is set to 1, the TH input is

ignored. If thermal monitoring is not required, either con-

nect a 10kΩ resistor between the TH pin and AGND or

write a 1 into DIS_TH.

Figure 13 shows the TH pin internal circuitry. When

thermal monitoring is enabled, the constant current

source flows through the external NTC resistor, which

gives a voltage vs temperature curve. The internal com-

parators give the ACT2861 information about the bat-

tery’s operating temperature.

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