Datasheet

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FUNCTIONAL DESCRIPTION
BatteryVoltage,
V
(BAT)
Charge
Complete
Status,
Charger
Off
VoltageRegulationand
ChargeTermination
Phase
PRE-CHARGE
CURRENT AND
TERMINATION
THRESHOLD
BatteryCurrent,
I
(BAT)
DONE
DONE
T
(CHG)
V
O(REG)
FAST-CHARGE
CURRENT
I I
O(PRECHG), (TERM)
I
O(OUT)
Current
Regulation
Phase
Pre-
Conditioning
Phase
v
(LOWV)
T
(PRECHG)
bq2406x
SLUS689A – JUNE 2006 – REVISED OCTOBER 2006
The charge current is programmable using external components (R
ISET
resistor). The charge process starts
when an external input power is connected to the system, the charger is enabled by CE = LO and the battery
voltage is below the recharge threshold, V(BAT) < V
(RCH)
. When the charge cycle starts a safety timer is
activated, if the safety timer function is enabled. The safety timer timeout value is set by an external resistor
connected to TMR pin.
When the charger is enabled two control loops modulate the battery switch drain to source impedance to limit
the BAT pin current to the programmed charge current value (charge current loop) or to regulate the BAT pin
voltage to the programmed charge voltage value (charge voltage loop). If V(BAT) < V(LOWV) (3 V typical) the
BAT pin current is internally set to 10% of the programmed charge current value.
A typical charge profile is shown below, for an operation condition that does not cause the IC junction
temperature to exceed T
J(REG)
, (112 ° C typical).
Figure 13. Charging Profile With T
J(REG)
If the operating conditions cause the IC junction temperature to exceed T
J(REG)
, the charge cycle is modified,
with the activation of the integrated thermal control loop. The thermal control loop is activated when an internal
voltage reference, which is inversely proportional to the IC junction temperature, is lower than a fixed,
temperature stable internal voltage. The thermal loop overrides the other charger control loops and reduces the
charge current until the IC junction temperature returns to T
J(REG)
, effectively regulating the IC junction
temperature.
9
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