ADP5063ACPZ-1-R7 datasheet(19/44 Pages) AD

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Data Sheet

ADP5063

Rev. 0 | Page 19 of 44

Trickle Charge Mode

A deeply discharged Li-Ion cell can exhibit a very low cell voltage,

making it unsafe to charge the cell at high current rates. The

ADP5063 charger uses a trickle charge mode to reset the battery

pack protection circuit and lift the cell voltage to a safe level for

fast charging. A cell with a voltage below VTRK_DEAD is charged

with the trickle mode current, ITRK_DEAD. During trickle charging

mode, the CHARGER_STATUS[2:0] bits are set.

During trickle charging, the ISO_Sx node is regulated to VISO_STRK

by the LDO and the battery isolation FET is off, which means

that the battery is isolated from the system power supply.

Trickle Charge Mode Timer

The duration of trickle charge mode is monitored to ensure that the

battery is revived from its deeply discharged state. If trickle charge

mode runs for longer than 60 minutes without the cell voltage

reaching VTRK_DEAD, a fault condition is assumed and charging stops.

The fault condition is asserted on the CHARGER_STATUS[2:0]

bits, allowing the user to initiate the fault recovery procedure

specified in the Fault Recovery section.

Weak Charge Mode (Constant Current)

When the battery voltage exceeds VTRK_DEAD but is less than

VWEAK, the charger switches to intermediate charge mode.

During the weak charge mode, the battery voltage is too low to

allow the full system to power up. Because of the low battery

level, the USB transceiver cannot be powered and, therefore,

cannot enumerate for more current from a USB host. Conse-

quently, the USB limit remains at 100 mA.

The system microcontroller may or may not be powered by the

charger output voltage (VISO_SFC), depending upon the amount

of current that the microcontroller and/or the system architecture

requires. When the ISO_Sx pins power the microcontroller, the

battery charge current (ICHG_WEAK) cannot be increased above

20 mA to ensure microcontroller operation (if doing so), nor

can ICHG_WEAK be increased above the 100 mA USB limit. There-

fore, set the battery charging current as follows:

•

Set the default 20 mA via the linear trickle charger branch (to

ensure that the microprocessor remains alive if powered by

the main charger output, ISO_Sx). Any residual current on

the main charger output, ISO_Sx, is used to charge the battery.

•

During weak current mode, other features may prevent the

weak charging current from reaching its full programmed

value. Isothermal charging mode or input current limiting

for USB compatibility can affect the programmed weak

charging current value under certain operating conditions.

During weak charging, the ISO_Sx node is regulated to

VISO_SFC by the battery isolation FET.

Fast Charge Mode (Constant Current)

When the battery voltage exceeds VTRK_DEAD and VWEAK, the charger

switches to fast charge mode, charging the battery with the constant

current, ICHG. During fast charge mode (constant current), the

CHARGER_STATUS[2:0] bits are set to 010.

During constant current mode, other features may prevent the

current, ICHG, from reaching its full programmed value. Isothermal

charging mode or input current limiting for USB compatibility

can affect the value of ICHG under certain operating conditions.

The voltage on ISO_Sx is regulated to stay at VISO_SFC by the

battery isolation FET when VISO_Bx < VISO_SFC.

Fast Charge Mode (Constant Voltage)

As the battery charges, its voltage rises and approaches the termi-

nation voltage, VTRM. The ADP5063 charger monitors the voltage

on the BAT_SNS pin to determine when charging should end.

However, the internal ESR of the battery pack combined with the

printed circuit board (PCB) and other parasitic series resis-

tances creates a voltage drop between the sense point at the

BAT_SNS pin and the cell terminal. To compensate for this

and to ensure a fully charged cell, the ADP5063 enters a constant

voltage charging mode when the termination voltage is detected

on the BAT_SNS pin. The ADP5063 reduces charge current

gradually as the cell continues to charge, maintaining a voltage of

VTRM on the BAT_SNS pin. During fast charge mode (constant

voltage), the CHARGER_ STATUS bits are set to 011.

Fast Charge Mode Timer

The duration of fast charge mode is monitored to ensure that

the battery is charging correctly. If the fast charge mode runs

for longer than tCHG without the voltage at the BAT_SNS pin

reaching VTRM, a fault condition is assumed and charging stops.

The fault condition is asserted on the CHARGER_STATUS[2:0]

bits, allowing the user to initiate the fault recovery procedure as

specified in the Fault Recovery section.

If the fast charge mode runs for longer than tCHG, and VTRM has

been reached on the BAT_SNS pin but the charge current has

not yet fallen below IEND, charging stops. No fault condition is

asserted in this circumstance, and charging resumes as normal

if the recharge threshold is breached.

Watchdog Timer

The ADP5063 charger features a programmable watchdog timer

function to ensure that charging is under the control of the pro-

cessor. The watchdog timer starts running when the ADP5063

charger determines that the processor should be operational,

that is, when the processor sets the RESET_WD bit for the first

time or when the battery voltage is greater than the weak battery

threshold, VWEAK. When the watchdog timer has been triggered,

it must be reset regularly within the watchdog timer period, tWD.

While in charger mode, if the watchdog timer expires without

being reset, the ADP5063 charger assumes that there is a software

problem and triggers the safety timer, tSAFE. For more information

see the Safety Timer section.

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