BQ32000 Datasheet, PDF (5/20 Pages) Texas Instruments – REAL-TIME CLOCK (RTC)

bq32000
www.ti.com................................................................................................................................................... SLUS900B – DECEMBER 2008 – REVISED JUNE 2009
DEVICE INFORMATION
IRQ Function
The IRQ pin of the bq32000 functions as a general-purpose output or a frequency test output. The function of
IRQ is configurable in the device register space by setting the FT, FTF, and OUT bits. On initial power cycles,
the OUT bit is set to one, and the FTF and FT bits are set to zero. On subsequent power-ups, with backup
supply present, the OUT bit remains unchanged, and the FTF and FT bits are set to zero. When operating on
backup supply, the IRQ pin function is unused. IRQ pullup resistor should be tied to V_CC to prevent IRQ operation
when operating on backup supply. The effect of the calibration logic is not normally observable when IRQ is
configured to output 1 Hz. The calibration logic functions by periodically adjusting the width of the 1-Hz clock.
The calibration effect is observable only every eight or sixteen minutes, depending on the sign of the calibration.
Figure 1. IRQ Pin Functional Diagram
Table 1. IRQ Function
FT
OUT
FTF
IRQ STATE
1
X
1
1 Hz
1
X
0
512 Hz
0
1
X
1
0
0
X
0
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