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

44 of 97

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ACT2861

30V Buck-Boost Charger with Integrated MOSFETs and OTG

®

bits OTG_BAT_ILIM[1:0] in register 0x10h scale the

current. See the Setting Charge Current section for

details on programming ICHG.

Table 8: OTG I2C Input Current Limit Setting

OTG_BAT_ILIM[1:0]

Register Setting

OTG Input Current

00

OTG Disabled

01

150% of ICHG

10

200% of ICHG

11

150% of ICHG

When the OTG output current exceeds the maximum

programmed value, the switching converter changes to

input constant current mode and regulates a fixed input

current. The OTG regulation mode can be monitored in

real time by I2C bit OTG_BATTERY_CC in register

0x20h. When this bit = 0, the IC is not in OTG constant

current mode. When this bit = 1, the IC is regulating in

input constant current mode. If the output drops below

3V, the IC assumes an output fault has occurred and

disables the output for 3s. It follows the same flow as an

output current fault.

OTG Mode VIN Over-Voltage Protection

When in OTG mode, the IC provides power out of the

IC’s input. An input voltage should not be applied during

OTG Mode. To detect a possible plug in of a higher sup-

ply on VIN during OTG mode, the IC detects an over-

voltage condition on VIN (OTG output) and immediately

stops switching. The OTG overvoltage threshold is fixed

at 108% of the programmed OTG voltage. If the OV

condition lasts for more than 100ms, the IC exits OTG

Mode and enters HIZ Mode.

OTG – Cord Compensation

ACT286x provides cord compensation at the OTG out-

put. This feature compensates for system level voltage

drops due to PCB, connector, and wiring resistances.

These resistances reduce the output voltage at the load.

The ACT286x features Cord Compensation which al-

lows the user to compensate for these system level re-

sistances by increasing the OTG voltage regulation set

point proportional to the OTG output current. The output

voltage increases linearly with increasing load current.

The I2C OTG_CORD_COMP[1:0] bits in register 0x0F

set the Cord Comp value.

The Cord Compensation value is normalized to RCS_IN =

10mΩ and a 2.4A OTG load current. It scales linearly

with changes in current sense resistance or load current.

Note that the RCS_IN resistor is both the charging input

current limit resistor and the OTG output current limit

resistor.

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Where VOTG_CORD_COMP is the I2C Cord Compensation

value of 100mV, 200mV, or 300mV per Table 9, IOTG is

the actual OTG output current in Amperes, and RCS_IN is

the current sense value in Ohms.

Table 9: OTG Cord Comp Setting

OTG_CORD_COMP[1:0]

Setting

Cord Comp

Value

Equivalent

System

Resistance

00

0 (Disabled)

0m

Ω

01

100mV

41.7m

Ω

10

200mV

83.3m

Ω

11

300mV

125.0m

Ω

Light Load Disable

The ACT2861 includes a Light Load Disable function in

OTG mode. This function disables OTG mode and puts

the IC into HIZ mode when the load drops very low. This

condition typically happens when the ACT2861 OTG

output is charging a portable device. When the portable

device is fully charged, the output current drops to 0A.

Light Load Disable minimizes battery current consump-

tion and extends battery life when the OTG output is not

needed.

Light Load Disable is available when the IC is operating

in OTG mode, the switcher is operating in buck mode,

VBAT is higher than VIN by a minimum of 0.5V, and the

OTG Output Voltage is less than 6V. Enable Light Load

Disable by setting I2C bit OTG_OFF_LOAD_EN in reg-

ister 0x0Eh = 1. Setting this bit = 0 disables the feature.

The minimum current is set to 5mA typical. The current

must be low for longer than the time set in I2C bit

OTG_OFF_DLY[1:0]. This time can programmed to 10s,

20s, or 30s.

Once the OTG state machine has detected a light load

condition, it enters the OTG_LL_DIS state. The IC must

exit OTG mode and re-enter OTG mode to restart the

converter. This is typically accomplished by toggling the

nOTG pin, but can also be accomplished via I2C.

OTG – Output Voltage DVS

The ACT2861 is ideally suited for many industry stand-

ard charging protocols such as USB PD3.0, QC2.0,