BQ24600_1 Datasheet, PDF (17/31 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Li-Ion or Li-Polymer Battery Charger with Low Iq

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VREF
bq24600
TS
RT 1
RT 2
RTH
103AT
bq24600
SLUS891 – FEBRUARY 2010
Figure 15. TS Resistor Network
Timer Fault Recovery
The bq24600 provides a recovery method to deal with timer fault conditions. The following summarizes this
method:
Condition 1: The battery voltage is above the recharge threshold and a timeout fault occurs.
Recovery Method: The timer fault will clear when the battery voltage falls below the recharge threshold, and
battery detection will begin. Taking CE low or a POR condition will also clear the fault.
Condition 2: The battery voltage is below the recharge threshold and a timeout fault occurs.
Recovery Method: Under this scenario, the bq24600 applies the I_FAULT current to the battery. This small current
is used to detect a battery removal condition and remains on as long as the battery voltage stays below the
recharge threshold. If the battery voltage goes above the recharge threshold, the bq24600 disables the fault
current and executes the recovery method described in Condition 1. Taking CE low or a POR condition will also
clear the fault.
PG Output
The open drain PG(power good) output indicates whether the VCC voltage is valid or not. The open drain FET
turns on whenever bq24600 has a valid VCC input (not in UVLO or ACOV or SLEEP mode). The PGpin can be
used to drive an LED or communicate to the host processor. It can also be used to drive ACFET and BATFET.
CE (Charge Enable)
The CE digital input is used to disable or enable the charge process. A high-level signal on this pin enables
charge, provided all the other conditions for charge are met (see Enabling and Disabling Charge). A high to
low transition on this pin also resets all timers and fault conditions. There is an internal 1 MΩ pull-down resistor
on the CE pin, so if CE is floated the charge will not turn on.
Inductor, Capacitor, and Sense Resistor Selection Guidelines
The bq24600 provides internal loop compensation. With this scheme, best stability occurs when the LC resonant
frequency, f_o, is approximately 17 kHz – 25 kHz for bq24600, per Equation 8:
1
f_o =
2p L_o C_o
(8)
Table 2 provides a summary of typical LC components for various charge currents.
Copyright © 2010, Texas Instruments Incorporated
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