BQ24070 Datasheet, PDF (19/26 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

bq24070
www.ti.com
SLUS694A – MARCH 2006 – REVISED MARCH 2006
FUNCTIONAL DESCRIPTIONS (continued)
V_{(SET−TREG)}
+
I_(OUT) R_(SET)
K_(SET)
(7)
All deglitch times also adjusted proportionally to t_(CHG-TREG).
Charge Termination and Recharge
The bq24070 monitors the voltage on the ISET1 pin, during voltage regulation, to determine when termination
should occur ©/10 – 250 mV). Once the termination threshold, I_(TERM), is detected the bq24070 terminates
charge. The resistor connected between the ISET1 and VSS, R_SET, programs the fast charge current level ©
level, V_ISET1 = 2.5 V) and thus the C/10 and C/25 current termination threshold level. The V_(TERM) and
K_(SET) parameters are specified in the specifications table. Note that this applies to both AC and USB charging.
I _(TERM)
+
V_(TERM) K_(SET)
R_SET
(8)
After charge termination, the bq24070 re-starts the charge once the voltage on the BAT pin falls below the V_(RCH)
threshold. This feature keeps the battery at full capacity at all times.
Sleep and Standby Modes
The bq24070 charger circuitry enters the low-power sleep mode if the input is removed from the circuit. This
feature prevents draining the battery into the bq24070 during the absence of input supply. Note that in sleep
mode, Q2 remains on (i.e., battery connected to the OUT pin) in order for the battery to continue supplying
power to the system.
The bq24070 enters the low-power standby mode if while input power is present, the CE input is low. In this
suspend mode, internal power FET Q1 (see Figure 4) is turned off, the BAT input is used to power the system
through the OUT pin. This feature is designed to limit the power drawn from the input supply (such as USB
suspend mode).
Charge Status Outputs
The open-drain (OD) STAT1 and STAT2 outputs indicate various charger operations as shown in Table 2.
These status pins can be used to drive LEDs or communicate to the host processor. Note that OFF indicates the
open-drain transistor is turned off. Note that this assumes CE = High.
Table 2. Status Pins Summary
CHARGE STATE
Precharge in progress
Fast charge in progress
Charge done
Charge suspend (temperature), timer fault, and sleep mode
STAT1
ON
ON
OFF
OFF
STAT2
ON
OFF
ON
OFF
PG, Outputs (Power Good)
The open-drain pin, PG, indicates when input power is present, and above the battery voltage. The
corresponding output turns ON (low) when exiting sleep mode (input voltage above battery voltage). This output
is turned off in the sleep mode (open drain). The PG pin can be used to drive an LED or communicate to the
host processor. Note that OFF indicates the open-drain transistor is turned off.
CE Input (Chip Enable)
The CE (chip enable) digital input is used to disable or enable the IC. A high-level signal on this pin enables the
chip, and a low-level signal disables the device and initiates the standby mode. The bq24070 enters the
low-power standby mode when the CE input is low with input present. In this suspend mode, internal power FET
Q1 (see block diagram) is turned off; the battery (BAT pin) is used to power the system via Q2 and the OUT pin.
This feature is designed to limit the power drawn from the input supply (such as USB suspend mode).
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