BQ24630 Datasheet, PDF (21/33 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Lithium Phosphate Battery Charger with System Power Selector and Low Iq

bq24630
www.ti.com
SLUS894 – JANUARY 2010
For example, 103AT NTC thermistor is used to monitor the battery pack temperature. Select T_COOL = 0ºC, T_WARM
= 60ºC. From the calculation and select standard 5% resistor value. We can get R_T1 = 2.2kΩ, R_T2 = 6.8kΩ, and
T_COLD is -17ºC (target -20ºC); T_HOT is 77ºC (target 75ºC), and T_CUT-OFF is 86ºC (target 80ºC). A small RC filter is
suggested to protect TS pin from system-level ESD.
Timer Fault Recovery
The bq24630 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 bq24630 applies the IFAULT 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 bq24630 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 bq24630 has a valid VCC input ( not in UVLO or ACOV or SLEEP mode). The PG pin can be
used to drive an LED or communicate to the host processor.
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 pulldown resistor on the
CE pin, so if CE is floated the charge will not turn on.
INDUCTOR, CAPACITOR, AND SENSE RESISTOR SELECTION GUIDELINES
The bq24630 provides internal loop compensation. With this scheme, best stability occurs when the LC resonant
frequency, f_o, is approximately 10kHz – 15kHz per Equation 9:
1
f_o =
2p L_o C_o
(9)
Table 2 provides a summary of typical LC components for various charge currents
Table 2. Typical Inductor, Capacitor, and Sense Resistor Values as a Function of Charge Current
CHARGE CURRENT
Output Inductor Lo
Output Capacitor Co
Sense Resistor
2A
8.2 mH
20 mF
10 mΩ
4A
8.2 mH
20 mF
10 mΩ
6A
5.6 mH
30 mF
10 mΩ
8A
4.7 mH
40 mF
10 mΩ
10A
4.7 mH
40 mF
10 mΩ
CHARGE STATUS OUTPUTS
The open-drain STAT1 and STAT2 outputs indicate various charger operations as shown in Table 3. These
status pins can be used to drive LEDs or communicate with the host processor. Note that OFF indicates that the
open-drain transistor is turned off.
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