BQ24050 Datasheet, PDF (20/37 Pages) Texas Instruments – 800mA Single Cell Li-Ion Battery Charger With Automatic Adaptor/USB Detection

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SLUS940A – SEPTEMBER 2009 – REVISED SEPTEMBER 2009.................................................................................................................................... www.ti.com
Power Good Indication (PG)
After application of a 5V source, the input voltage rises above the UVLO and sleep thresholds (V_IN>V_OUT+V_DT),
but is less than OVP (V_IN<V_OVP), then the PG FET turns on and provides a low impedance path to ground. SEE
Figure 5, Figure 6, and Figure 18.
CHG Pin Indication
The charge pin has an internal open drain FET which is on (pulls down to V_SS) during the first charge only
(independent of TTDM) and is turned off once the battery reaches voltage regulation and the charge current
tapers to the termination threshold set by the PRE-TERM resistor.
The charge pin will be high impedance in sleep mode and OVP (if PG is high impedance) and return to its
previous state once the condition is removed.
Cycling input power, pulling the TS pin low and releasing or entering pre-charge mode will cause the CHG pin to
reset and is considered the start of a first charge.
CHG and PG LED Pull-up Source
For host monitoring, a pull-up resistor is used between the "STATUS" pin and the V_CC of the host and for a visual
indication a resistor in series with an LED is connected between the "STATUS" pin and a power source. If the
CHG or PG source is capable of exceeding 7V, a 6.2V zener should be used to clamp the voltage. If the source
is the OUT pin, note that as the battery changes voltage, the brightness of the LEDs vary.
Charging State
1st Charge
Refresh Charge
OVP
SLEEP
TEMP FAULT
CHG FET/LED
ON
OFF
ON for 1st Charge
V_IN Power Good State
UVLO
PG FET/LED
SLEEP Mode
OFF
OVP Mode
Normal Input (V_OUT + V_DT < V_IN <
V_OUP)
ON
PG is independent of chip disable (bq24055, V_TS = 0V)
Input DPM Mode (V_IN-DPM or IN-DPM)
The IN-DPM feature is used to detect an input source voltage that is folding back (voltage dropping), reaching its
current limit due to an excessive load. When the input voltage drops to the V_IN-DPM threshold the internal pass
FET starts to reduce the current until there is no further drop in voltage at the input. This would prevent a source
with voltage less than V_IN-DPM to power the out pin. This works well with current limited adaptors and USB ports
as long as the nominal voltage is above 4.3V and 4.4V respectively. This is an added safety feature that helps
protect the source from excessive loads.
OUT
The Charger’s OUT pin provides current to the battery and to the system, if present. This IC can be used to
charge the battery plus power the system, charge just the battery or just power the system (TTDM) assuming the
loads do not exceed the available current. The OUT pin is a current limited source and is inherently protected
against shorts. If the system load ever exceeds the output programmed current threshold, the output will be
discharged unless there is sufficient capacitance or a charged battery present to supplement the excessive load.
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