Datasheet

V
5 V Adapter
rated for 750 mA
IN
I
IN
V
SYS
I
BAT
I
SYS
bq24272
www.ti.com SLUSB09 –JUNE 2012
Figure 7. bq24272 V
IN
-DPM
Bad Source Detection
When a source is connected to IN, the bq24272 runs a Bad Source Detection procedure to determine if the
source is strong enough to provide some current to charge the battery. A current sink is turned on (75mA) for
32ms. If the source is valid after the 32ms (V
BADSOURCE
< V
IN
< V
OVP
), the buck converter starts up and normal
operation continues. If the supply voltage falls below V
BAD_SOURCE
during the detection, the current sink shuts off
for 2s and then retries, a single 128μs pulse is sent on the STAT and INT outputs and the STATx and FAULT_x
bits of the status registers and the battery/supply status registers are updated in the I
2
C. The detection circuits
retries continuously until either a new source is connected to the other input or a valid source is detected after
the detection time. If during normal operation the source falls to V
BAD_SOURCE
, the bq24272 turns off the PWM
converter, turns the battery FET and BGATE on, sends a single 128μs pulse is sent on the STAT and INT
outputs and the STATx and FAULT_x bits of the status registers and the battery/supply status registers are
updated in the I
2
C. Once a good source is detected, the STATx and FAULT_x bits are cleared and the device
returns to normal operation.
Input Over-Voltage Protection
The bq24272 provides over-voltage protection on the input that protects downstream circuitry. The built-in input
over-voltage protection to protect the device and other components against damage from overvoltage on the
input supply (Voltage from V
IN
to PGND). During normal operation, if V
IN
> V
OVP
, the bq24272 turns off the PWM
converter, turns the battery FET and BGATE on, sends a single 128μs pulse is sent on the STAT and INT
outputs and the STATx and FAULT_x bits of the status registers and the battery/supply status registers are
updated in the I
2
C. Once the OVP fault is removed, the STATx and FAULT_x bits are cleared and the device
returns to normal operation.
Charge Status Outputs (STAT, INT)
The STAT output is used to indicate operation conditions for bq24272. STAT is pulled low during charging when
EN_STAT bit in the control register (0x02h) is set to “1”. When charge is complete or disabled, STAT is high
impedance. When a fault occurs, a 128-µs pulse (interrupt) is sent out to notify the host. The status of STAT
during different operation conditions is summarized in Table 1. STAT drives an LED for visual indication or can
be connected to the logic rail for host communication. The EN_STAT bit in the control register (00H) is used to
enable/disable the charge status for STAT. The interrupt pulses are unaffected by EN_STAT and will always be
shown. The INT output is identical to STAT and is used to interface with a low voltage host processor.
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