bq24030, bq24031, bq24032,
bq24032A, bq24035, bq24038, bq24039
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SLUS618C–AUGUST 2004–REVISED JUNE 2005
Charge Termination and Recharge
The bqTINY-III monitors the voltage on the ISET1 pin, during voltage regulation, to determine when termination
should occur (C/10 – 250 mV, C/25 – 100 mV). Once the termination threshold, I(TERM), is detected the bqTINY-III
terminates charge. The resistor connected between the ISET1 and VSS, RSET, programs the fast charge current
level (C level, VISET1 = 2.5 V) and thus the C/10 and C/25 current termination threshold levels. The V(TERM) and
K(SET) parameters are specified in the specifications table. Note that this applies to both AC and USB charging.
V
K
(SET)
(TERM)
I
+
(TERM)
R
SET
(8)
After charge termination, the bqTINY-III re-starts the charge once the voltage on the OUT pin falls below the
V(RCH) threshold. This feature keeps the battery at full capacity at all times.
LDO Regulator
The bqTINY-III provides a 3.3-V LDO regulator. This regulator is typically used to power USB transceiver or
drivers in portable applications. Note that this LDO is only enabled when either AC or USB inputs are present. If
the CE pin is low (chip disabled) and AC or USB is present, the LDO is powered by the battery. This is to ensure
low input current when the chip is disabled.
Sleep and Standby Modes
The bqTINY-III charger circuitry enters the low-power sleep mode if both AC and USB are removed from the
circuit. This feature prevents draining the battery into the bqTINY-III during the absence of input supplies. 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 bqTINY-III enters the low-power standby mode if while AC or USB is present, the CE input is low. In this
suspend mode, internal power FETs Q1 and Q3 (see the block diagram) are turned off, the BAT input is used to
power the system through OUT pin, and the LDO remains on (powered from output). This feature is designed to
limit the power drawn from the input supplies (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
STAT1
ON
STAT2
ON
Fast charge in progress
ON
OFF
ON
Charge done
OFF
OFF
Charge suspend (temperature), timer fault, and sleep mode
OFF
ACPG, USBPG Outputs (Power Good), bq24030/1/2/2A/5/9
The two open-drain pins, ACPG, USBPG (AC and USB power good), indicate when the AC adapter or USB port
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 ACPG,
USBPG pins can be used to drive an LED or communicate to the host processor. Note that OFF indicates the
open-drain transistor is turned off.
PG Output (Power Good), bq24038
The open-drain pin PG indicates when either the AC adapter or USB port is present and above the battery
voltage. This output is turned off in sleep mode (open drain). The PG pin can be used to drive a LED or
communicate with the host processor.
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