BQ24100_08 Datasheet, PDF (18/38 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs (bqSWITCHER™)

bq24100, bq24103, bq24103A
bq24104, bq24105, bq24108, bq24109
bq24113, bq24113A, bq24115
SLUS606N – JUNE 2004 – REVISED NOVEMBER 2008 .................................................................................................................................................. www.ti.com
Timer Fault Recovery
As shown in FIGURE 10, bqSWITCHER provides a recovery method to deal with timer fault conditions. The
following summarizes this method.
Condition 1 V_I(BAT) above recharge threshold (V_OREG - V_RCH) and timeout fault occurs.
Recovery method: bqSWITCHER waits for the battery voltage to fall below the recharge threshold. This could
happen as a result of a load on the battery, self-discharge or battery removal. Once the battery falls below the
recharge threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or
CE toggle also clears the fault.
Condition 2 Charge voltage below recharge threshold (V_OREG – V_RCH) and timeout fault occurs
Recovery method: Under this scenario, the bqSWITCHER applies the I_DETECT current. 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, then the bqSWITCHER disables the I_DETECT
current and executes the recovery method described in Condition 1. Once the battery falls below the recharge
threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or CE toggle
also clears the fault.
Output Overvoltage Protection (Applies To All Versions)
The bqSWITCHER provides a built-in overvoltage protection to protect the device and other components against
damages if the battery voltage gets too high, as when the battery is suddenly removed. When an overvoltage
condition is detected, this feature turns off the PWM and STATx pins. The fault is cleared once V_IBAT drops to the
recharge threshold (V_OREG – V_RCH).
Functional Description for System-Controlled Version (bq2411x)
For applications requiring charge management under the host system control, the bqSWITCHER (bq2411x)
offers a number of control functions. The following section describes these functions.
Precharge And Fast-Charge Control
A low-level signal on the CMODE pin forces the bqSWITCHER to charge at the precharge rate set on the ISET2
pin. A high-level signal forces charge at fast-charge rate as set by the ISET1 pin. If the battery reaches the
voltage regulation level, V_OREG, the bqSWITCHER transitions to voltage regulation phase regardless of the status
of the CMODE input.
Charge Termination And Safety Timers
The charge timers and termination are disabled in the system-controlled versions of the bqSWITCHER. The host
system can use the CE input to enable or disable charge. When an overvoltage condition is detected, the
charger process stops, and all power FETs are turned off.
Inductor, Capacitor, and Sense Resistor Selection Guidelines
The bqSWITCHER provides internal loop compensation. With this scheme, best stability occurs when LC
resonant frequency, f_o is approximately 16 kHz (8 kHz to 32 kHz). Equation 9 can be used to calculate the value
of the output inductor and capacitor. Table 3 provides a summary of typical component values for various charge
rates.
Ǹ ^{f0 +} _2p
1
L_OUT
C_OUT
(9)
CHARGE CURRENT
Output inductor, L_OUT
Output capacitor, C_OUT
Sense resistor, R_(SNS)
Table 3. Output Components Summary
0.5 A
22 µH
4.7 µF
0.2 Ω
1A
10 µH
10 µF
0.1 Ω
2A
4.7 µH
22 µF (or 2 × 10 µF) ceramic
0.05 Ω
18
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