ACT8810 datasheet(45/54 Pages) ACTIVE-SEMI

45 / 54 page

ActivePath

TM CHARGER

ACT8810

Rev 9, 15-Nov-12

Innovative Power

- 45 -

www.active-semi.com

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

2CTM is a trademark of NXP.

ACIN CHGLEV

CHARGE

CURRENT

ICHG (mA)

PRECONDITION

CHARGE CURRENT

ICHG (mA)

90mA or ISET

(Smallest one)

90mA or 12%ISET

(Smallest one)

450mA or ISET

(Smallest one)

12% × ISET

50% × ISET

12% × ISET

ISET

12% × ISET

FUNCTIONAL DESCRIPTION CONT’D

two current-limited nSTAT0 and nSTAT1 outputs

that can directly drive LED indicators or provide a

logic-level status signal to the host microprocessor

Dynamic Charge Current Control (DCCC)

The

ACT8810's

ActivePath

Charger

features

Dynamic Charge Current Control (DCCC) circuitry,

which continuously monitors the input supply to

prevent input overload conditions. DCCC reduces

the charge current when the VSYS voltage

decreases to VDCCC and stops charging when VSYS

drops below VDCCC by 1.5% (typical).

The DCCC voltage threshold is programmed by

connecting a resistor from DCCC to GA according

to the following equation:

VDCCC = 2 × (IDCCC × RDCCC)

(2)

Where RDCCC is the value of the external resistor,

and IDCCC (100µA typical) is the value of the current

sourced from DCCC.

Given the tolerances of the RDCCC and IDCCC ,the

DCCC voltage threshold should be programmed to

be no less than 3.3V to prevent triggering the

UVLO, and to be no larger than 4.4V to prevent

engaging DCCC prematurely. A 19.1k (1%), or

18.7k (1%) resistor for RDCCC is recommended.

Charger Current Programming

The ACT8810's ActivePath charger features a

flexible charge current-programming scheme that

combines the convenience of internal charge

current programming with the flexibility of resistor

based charge current programming. Current limits

and charge current programming are managed as a

function of the ACIN and CHGLEV pins, in

combination with RISET, the resistance connected to

the ISET pin.

ACIN and CHGLEV Inputs

ACIN is a logic input that configures the current-limit

of ActivePath's linear regulator as well as that of the

battery charger. ACIN features a precise 1.25V

logic threshold, so that the input voltage detection

threshold may be adjusted with a simple resistive

voltage divider. This input also allows a simple, low-

cost dual-input charger switch to be implemented

with just a few, low-cost components.

When ACIN is driven to a logic high, the ActivePath

operates in “AC-Mode” and the charger charges at

the current programmed by RISET,

ISET (mA) = KISET × 1V/(RISET (kΩ) +0.031)

(3)

where KISET = 628 when CHGLEV is driven to a

logic high, and KISET = 314 when CHGLEV is driven

to a logic low.

When ACIN is driven to a logic-low, the ActivePath

circuitry operates in “USB-Mode”, which enforces a

maximum charge current setting of 500mA, if

CHGLEV is driven to a logic-high, or 100mA, if

CHGLEV is driven to a logic-low.

The ACT8810's charge current settings are

summarized in the table below:

Table 19:

ACIN and CHGLEV Inputs Table

Note that the actual charging current may be limited

to a current that is lower than the programmed fast

charge current due to the ACT8810’s internal

thermal

regulation

loop.

See

the

Thermal

Regulation

and Protection section for more

information.

Battery Temperature Monitoring

The

ACT8810

continuously

monitors

the

temperature of the battery pack by sensing the

resistance of its thermistor, and suspends charging

if the temperature of the battery pack exceeds the

safety limits.

In a typical application, shown in Figure 11, the TH

pin is connected to the battery pack's thermistor

input. The ACT8810 injects a 100µA current out of the

TH pin into the thermistor, so that the thermistor

resistance is monitored by comparing the voltage at

TH to the internal VTHH and VTHL thresholds of 0.5V

and 2.5V, respectively. When VTH > VTHL or VTH < VTHH

charging and the charge timers are suspended. When

VTH returns to the normal range, charging and the

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