AAT3687_08 Datasheet, PDF (15/20 Pages) Advanced Analogic Technologies – Lithium-Ion/Polymer Battery Charger

BatteryManager^TM
PRODUCT DATASHEET
AAT3687
Lithium-Ion/Polymer Battery Charger
1.8V to 5.0V
IN
AAT3687
Status
Control
OUT
DATA Pin
R_{PULL_UP}
GPIO
Figure 3: Data Pin Application Circuit.
IN
OUT
µP GPIO
Port
The DATA pin function logic is active low and should nor-
mally be pulled high to V_ADP. This data line can also be
pulled high to the same level as the high state for the
logic I/O port on the system microcontroller. In order for
the DATA pin control circuit to generate clean, sharp
edges for the data output, and to maintain the integrity
of the data timing for the system, the pull-up resistor on
the data line should be low enough in value so that the
DATA signal returns to the high state without delay. If
the pull-up resistor is too high, the strobe pulse from the
system microcontroller could exceed the maximum pulse
time and the DATA output control could issue false status
reports. A 1.5kΩ resistor is recommended when pulling
the DATA pin high to 5.0V on the V_ADP input. If the data
line is pulled high to a voltage level less than 5.0V, the
pull-up resistor can be calculated based on a recom-
mended minimum pull-up current of 3mA. Use the fol-
lowing formula:
Eq. 4: R_PULL-UP ≤
V_PULL-UP
3mA
Data Timing
The system microcontroller should assert an active low
data request pulse for minimum duration of 200ns; this
is specified by T_LO(DATA). Upon sensing the rising edge of
the end of the data request pulse, the AAT3687 status
data control will reply the data word back to the system
microcontroller after a delay specified by the data report
time specification T_DATA(RPT). The period of the following
group of data pulses will be specified by T_DATA.
Timing Diagram
SQ
SQ_PULSE
System Reset
System Start
P_DATA
CK
T_SYNC
T_LAT
T_OFF
Data
T_DATA(RPT) = T_SYNC + T_LAT < 2.5 P_DATA
T_OFF > 2 P_DATA
N=1
N=2
N=3
3687.2008.04.1.12
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