BQ24090_12 Datasheet, PDF (20/34 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion and Li-Pol Battery Charger

bq24090, bq24091
bq24092, bq24093
bq24095
SLUS968D – JANUARY 2010 – REVISED DECEMBER 2012
www.ti.com
TS
The bq2409x family contains an NTC monitoring function. The TS function for bq24090, bq24091 and bq24095
follow the classic temperature range and disable charge when the battery temperature outside of the 0°C and
45°C operating temperature window. The TS function for bq24092 and bq24093 are designed to follow the new
JEITA temperature standard for Li-Ion and Li-Pol batteries. There are now four thresholds, 60°C, 45°C, 10°C,
and 0°C. Normal operation occurs between 10°C and 45°C. If between 0°C and 10°C the charge current level is
cut in half and if between 45°C and 60°C the regulation voltage is reduced to 4.1Vmax, see Figure 21.
The bq2409x family has devices to monitor 10k and 100k NTC thermistors. The bq24090/2/5 are designed to
work with a 10k NTC. For these devices, the TS feature is implemented using an internal 50μA current source to
bias the thermistor (designed for use with a 10k NTC β = 3370 (SEMITEC 103AT-2 or Mitsubishi TH05-3H103F)
connected from the TS pin to V_SS. If this feature is not needed, a fixed 10k can be placed between TS and V_SS to
allow normal operation. This may be done if the host is monitoring the thermistor and then the host would
determine when to pull the TS pin low to disable charge. The bq24091/3 are designed to work with a 100k NTC.
For these devices, the TS feature is implemented using an internal 5μA current source to bias the thermistor
(designed for use with a 100k NTC β = 3370) connected from the TS pin to V_SS. If this feature is not needed, a
fixed 100k can be placed between TS and V_SS to allow normal operation. This may be done if the host is
monitoring the thermistor and then the host would determine when to pull the TS pin low to disable charge.
The TS pin has two additional features, when the TS pin is pulled low or floated/driven high. A low disables
charge (similar to a high on the BAT_EN feature) and a high puts the charger in TTDM.
Above 60°C or below 0°C the charge is disabled. Once the thermistor reaches ≈–10°C the TS current folds back
to keep a cold thermistor (between –10°C and –50°C) from placing the IC in the TTDM mode. If the TS pin is
pulled low into disable mode, the current is reduced to ≈30μA, see Figure 19. Since the I_TS current is fixed along
with the temperature thresholds, it is not possible to use thermistor values other than the 10k or 100k (depending
on the IC) NTC (at 25°C).
Termination and Timer Disable Mode (TTDM) -TS pin high
The battery charger is in TTDM when the TS pin goes high from removing the thermistor (removing battery
pack/floating the TS pin) or by pulling the TS pin up to the TTDM threshold.
When entering TTDM, the 10 hour safety timer is held in reset and termination is disabled. A battery detect
routine is run to see if the battery was removed or not. If the battery was removed then the CHG pin will go to its
high impedance state if not already there. If a battery is detected the CHG pin does not change states until the
current tapers to the termination threshold, where the CHG pin goes to its high impedance state if not already
there (the regulated output will remain on).
The charging profile does not change (still has pre-charge, fast-charge constant current and constant voltage
modes). This implies the battery is still charged safely and the current is allowed to taper to zero.
When coming out of TTDM, the battery detect routine is run and if a battery is detected, then a new charge cycle
begins and the CHG LED turns on.
If TTDM is not desired upon removing the battery with the thermistor, one can add a 237k resistor between TS
and V_SS to disable TTDM. This keeps the current source from driving the TS pin into TTDM. This creates ≈0.1°C
error at hot and a ≈3°C error at cold.
Timers
The pre-charge timer is set to 30 minutes. The pre-charge current, can be programmed to off-set any system
load, making sure that the 30 minutes is adequate.
The fast charge timer is fixed at 10 hours and can be increased real time by going into thermal regulation, IN-
DPM or if in USB current limit. The timer clock slows by a factor of 2, resulting in a clock than counts half as fast
when in these modes. If either the 30 minute or ten hour timer times out, the charging is terminated and the CHG
pin goes high impedance if not already in that state. The timer is reset by disabling the IC, cycling power or going
into and out of TTDM.
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