ACT3704YH-T データシートの表示（PDF） - Active-Semi, Inc

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ACT3704YH-T

12V Linear-Mode Battery Charger for Li+/Li-polymer Cells

Active-Semi, Inc 

ACT3704

Rev2, 26-Jul-07

Top-Off State

In the TOP-OFF state, the cell is charged in con-

stant-voltage (CV) mode, with the charge current

limited by the internal chemistry of the cell, decreas-

ing as charging continues.

If the ACT3704 state machine does not complete a

charging cycle before the TOP-OFF Timeout period

(TTOPOFF) expires, then a damaged cell is detected

and the state machine jumps to the TIMEOUT-

FAULT State.

The TOP-OFF Timeout period is default to 60mins

with a 2.2nF CTIMER capacitor, or it can be increased

with a larger value external capacitor. See the

Safety Timers section for more information.

In TOP-OFF state, nSTAT indicates charge com-

plete but charge current still continues. After another

delay of 60mins, then charging stops and charge

current becomes zero. When the battery voltage

drops below the charge restart voltage, the charging

process will start again.

End of Charge State

In the End of Charge (EOC) state, the ACT3704

presents a high-impedance to the battery, allowing

the cell to “relax” and minimize battery leakage cur-

rent. The ACT3704 continues to monitor the cell

voltage, however, so that it can reinitiate charging

cycles as necessary to ensure that the cell remains

fully charged.

Charge Restart

Under normal operation, the state machine initiates

a new charging cycle by jumping to the NORMAL

CHARGE state when VBAT drops below the Charge

Termination Threshold by more than the Charge Re-

start Threshold of 100mV (typ).

Timeout-Fault State

In TIMEOUT-FAULT state, both nSTAT and nEOC

indicators are OFF, or high-Z.

For a logic-level indication, simply connect a resistor

from each output to an appropriate voltage supply.

Reverse Battery & Shutdown

The ACT3704 includes internal circuitry that elimi-

nates the need for series blocking diodes, reducing

solution size and cost as well as dropout voltage

relative to conventional battery chargers. When VIN

goes below the ACT3704’s under voltage-lockout

(UVLO) voltage, or when VIN drops below VBAT, the

ACT3704 automatically goes into SUSPEND mode

and reconfigures its power switch to minimize cur-

rent drain from the battery.

Safety Timers

The ACT3704 has several internal charge safety

timers, for each of the PRECONDITION and NOR-

MAL charge states as well as TOPOFF timeout pe-

riod. If any of these timers expire before charge suc-

cessfully proceeds through the associated state, the

ACT3704 enters the TIMEOUT-FAULT state. The

TIMEOUT-FAULT state can only be reset by power-

cycling the ACT3704.

Each of these timers are internally set according to

the following ratios:

TPRECONDITION = 1 ×TO

(9)

TNORMAL = 1.5 ×TO

(10)

TTOTAL = 3 × TO

(11)

All the timers could be set by an external capacitor

by (CTIMER in nF) where TO is given by:

TO = 9 × CTIMER ±15%

(12)

When operating in thermal regulation mode the

timeout periods are extended in order to compen-

sate for the effect of the reduced charging current

on total charge time. In order to ensure a safe

charge, the maximum timeout periods are limited to

2x the room temperature values.

Charge and EOC Status Outputs

nSTAT and nEOC are open-drain outputs that sink

current when asserted and are high-Z otherwise. For

more information regarding the state of nSTAT and

nEOC throughout the entire charging cycle, see Ta-

ble 3. These outputs have internal 7mA current lim-

its, and are capable of directly driving LEDs, without

the need of current-limiting resistors or other exter-

nal circuitry, for a visual charge-status indication. To

drive an LED, simply connect the LED between

each pin and an appropriate supply (typically VIN).

Innovative Products. Active Solutions.

- 10 -

www.active-semi.com

Copyright © 2007 Active-Semi, Inc.

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