Datasheet

TPS65217A, TPS65217B, TPS65217C, TPS65217D
www.ti.com SLVSB64F –NOVEMBER 2011–REVISED APRIL 2013
Charge Termination
When the charging current drops below the termination current threshold, the charger is turned off. The value of
the termination current threshold can be set in register CHGCONFIG3 using bits TERMIF[1:0]. The termination
current has a default setting of 7.5% of the ICHRG[1:0] setting.
Charge termination is disabled by default and can be enabled by setting the TERM bit or the CHGCONFIG1
register to 1. When termination is disabled, the device goes through the pre-charge, fast-charge and CV phases,
then remains in the CV phase. The charger behaves like an LDO with an output voltage equal to V
OREG
, able to
source current up to I
CHG
or I
IN-MAX
, whichever is less. Battery detection is not performed.
NOTE
Termination current threshold is not a tightly controlled parameter. Using the lowest setting
(2.5% of nominal charge current) is not recommended because the minimum termination
current can be very close to 0. Any leakage on the battery-side may cause the termination
not to trigger and charging to time-out eventually.
Battery Detection and Recharge
Whenever the battery voltage falls below V
RCH
, I
BAT(DET)
is pulled from the battery for a duration t
DET
to determine
if the battery has been removed. If the voltage on the BAT pin remains above V
LOWV
, it indicates that the battery
is still connected. If the charger is enabled (CH_EN = 1), a new battery charging cycle begins.
If the BAT pin voltage falls below V
LOWV
in the battery detection test, it indicates that the battery has been
removed. The device then checks for battery insertion: it turns on the charging path and sources I
PRECHG
out of
the BAT pin for duration t
DET
. If the voltage does not rise above V
RCH
, it indicates that a battery has been
inserted, and a new charge cycle can begin. If, however, the voltage does rise above V
RCH
, it is possible that a
fully charged battery has been inserted. To check for this, I
BAT(DET)
is pulled from the battery for t
DET
and if the
voltage falls below V
LOWV
, no battery is present. The battery detection cycle continues until the device detects a
battery or the charger is disabled.
When the battery is removed from the system the charger will also flag a BATTEMP error indicating that the TS
input is not connected to a thermistor.
Safety Timer
The TPS65217 hosts internal safety timer for the pre-charge and fast-charge phases to prevent potential damage
to either the battery or the system. The default fast-charge time can be changed in register CHGCONFIG1 and
the precharge time in CHGCONFIG3. The timer functions can be disabled by resetting the TMR_EN bit of the
CHGCONFIG1 register to 0. Note that both timers are disabled when charge termination is disabled (TERM = 0).
Dynamic Timer Function
Under some circumstances the charger current is reduced to react to changes in the system load or junction
temperature. The two events that can reduce the charging current are:
• The system load current increases, and the DPM loop reduces the available charging current.
• The device has entered thermal regulation because the IC junction temperature has exceeded T
J(REG)
.
In each of these events, the timer is clocked with half frequency to extend the charger time by a factor of 2 and
charger termination is disabled. Normal operation resumes after IC junction temperature has cooled off and/or
the system load drops to a level where enough current is available to charge the battery at the desired charge
rate. This feature is enabled by default and can be disabled by resetting the DYNTMR bit in the CHGCONFIG2
register to 0. A modified charge cycle with the thermal loop active is shown in Figure 10.
Timer Fault
A timer fault occurs if:
• If the battery voltage does not exceed V
LOWV
in time t
PRECHG
during pre-charging.
• If the battery current does not reach I
TERM
in fast charge before the safetimer expires. Fast-charge time is
measured from the beginning of the fast charge cycle.
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