BQ24700_14 Datasheet, PDF (23/32 Pages) Texas Instruments – NOTEBOOK PC BATTERY CHARGE CONTROLLER

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bq24700, bq24701
NOTEBOOK PC BATTERY CHARGE CONTROLLER
AND SELECTOR WITH DPM
SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002
APPLICATION INFORMATION
smart learn cycles when adapter power is present
Smart learn cycles can be conducted when adapter power is present by asserting and maintaining the ACSEL
pin low. The adapter power can be reselected at the end of the learn cycle by a setting ACSEL to a logic high,
provided that adapter power is present. Battery charging is suspended while selected as the system power
source.
When selecting the battery as the system primary power source, the adapter power select MOSFET turns off,
in a break-before-make fashion, before the battery select MOSFET turns on. To ensure that this happens under
all load conditions, the system voltage (load voltage) can be monitored through a resistor divider on the VS pin.
This function provides protection against switching over to battery power if the adapter selector switch were
shorted and adapter power present. This function can be eliminated by grounding the VS pin. During the
transition period from battery to adapter or adapter to battery, power is supplied to the system through the body
diode of the battery select switch.
battery depletion detection
The bq24700/bq24701 provides the host controller with a battery depletion discrete, the ALARM pin, to alert
the host when a depleted battery condition occurs. The battery depletion level is set by the voltage applied to
the BATDEP pin through a voltage divider network. The ALARM output asserts high and remains high as long
as the battery deplete condition exists regardless of the power source selected.
For the bq24700, the host controller must take appropriate action during a battery deplete condition to select
the proper power source. The bq24700 remains on the selected power source. The bq24700, however,
automatically reverts over to adapter power, provided the adapter is present, during a deep discharge state. The
battery is considered as being in a deep discharge state when the battery voltage is less than (0.8 × depleted
level).
The bq24701 automatically switches back to adapter power if a battery deplete condition exists, provided that
the adapter is present. Feature sets for the bq24700 and bq24701 are detailed in Table 1.
Table 1. Available Options
Condition
–40 C TA 85 C
Battery as Power Source
Battery removal
Battery reinserted
ac as Power Source
AC removal
AC reinserted
Depleted Battery Condition
Battery as power source
AC as power source
ALARM Signal Active
Selector Operation
bq24700PW
bq24701PW
Automatically selects ac
Selection based on selector inputs
Automatically selects ac
Battery is selected when ac is
removed
Automatically selects battery
Selection based on selector inputs
Automatically selects battery
Selection based on selector inputs
Sends ALARM signal
Sends ALARM signal
Automatically selects ac
Sends ALARM signal
Sends ALARM signal
Depleted battery condition
Depleted battery condition
Selector inputs do not match selector outputs
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