
www.ti.com
Battery Voltage Regulation
Charge Termination and Recharge
Sleep Mode
PG Output
TPS65014
SLVS551 – DECEMBER 2004
DETAILED DESCRIPTION (continued)
The voltage regulation feedback is through the VBAT pin. This pin is tied directly to the positive side of the
battery pack. The TPS65014 monitors the battery-pack voltage between the VBAT and AGND pins. The
TPS65014 is offered in a fixed-voltage version of 4.2 V.
As a safety backup, the TPS65014 also monitors the charge time in the fast-charge mode. If taper current is not
detected within this time period, t(CHG), the TPS65014 turns off the charger and indicates FAULT in the
CHGSTATUS register. In the case of a FAULT condition, the TPS65014 reduces the current to I(DETECT). I(DETECT)
is used to detect a battery replacement condition. Fault condition is cleared by POR via the serial interface. Note
that the safety timer is reset if the TPS65014 is forced out of the voltage regulation mode. The fast-charge timer
is disabled by default to allow charging during normal operation of the end equipment. It is enabled via the
CHGCONFIG register.
The TPS65014 monitors the charging current during the voltage regulation phase. Once the taper threshold,
I(TAPER), is detected, the TPS65014 initiates the taper timer, t(TAPER). Charge is terminated after the timer expires.
The TPS65014 resets the taper timer in the event that the charge current returns above the taper threshold,
I(TAPER). After a charge termination, the TPS65014 restarts the charge once the voltage on the VBAT pin falls
below the V(RCH) threshold. This feature keeps the battery at full capacity at all times. The fast charge timer and
the taper timer must be enabled by programming CHGCONFIG(5)=1. A thermal suspend suspends the
fast-charge and taper timers.
In addition to the taper current detection, the TPS65014 terminates charge in the event that the charge current
falls below the I(TERM) threshold. This feature allows for quick recognition of a battery removal condition. When a
full battery is replaced with an empty battery, the TPS65014 detects that the VBAT voltage is below the recharge
threshold and starts charging the new battery. The taper and termination bits are cleared in the CHGSTATUS
register and if the INT pin is still active due to these two interrupt sources, then it is de-asserted. Depending on
the transient seen at the VCC pin, all registers may be set to their default values and require reprogramming with
any nondefault values required, such as enabling the fast-charge timer and taper termination; this should only
happen if VCC drops below approximately 2 V.
The TPS65014 charger enters the low-power sleep mode if both input sources are removed from the circuit. This
feature prevents draining the battery during the absence of input power.
The open-drain, power-good (PG) output indicates when a valid power supply is present for the charger. This can
be either from the ac adapter input or from the USB. The output turns ON when a valid voltage is detected. A
valid voltage is detected whenever the voltage on either pin AC or pin USB rises above the voltage on VBAT
plus 100 mV. This output is turned off in the sleep mode. The PG pin can be used to drive an LED or
communicate to the host processor. A voltage greater than the V(CHGOVLO) threshold (typ 7 V) at the AC input is
not valid and does not activate the PG output. The PG output is held in high impedance state if the charger is in
reset by programming CHGCONFIG(6)=1.
The PG output can also be programmed via the LED1_ON and LED1_PER registers in the serial interface. It can
then be programmed to be permanently on, off, or to blink with defined on- and period-times. PG is controlled per
default via the charger.
21