AAT3670 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT3670' PDF : 32 Pages View PDF
If the use of the battery temperature sense function
is not required, it may be disabled by disconnecting
the VTS pin from the TS pin and terminating the TS
pin to ground. The VTS pin can be left floating.
Battery Charge Status Indication
The AAT3670 indicates the status of the battery
under charge using two status LED driver outputs.
These two LEDs can indicate simple functions
such as no battery charge activity, battery charg-
ing, charge complete and charge fault.
Status Indicator Display
System charging status may be displayed using
one or two LEDs in conjunction with the STAT1 and
STAT2 pins on the AAT3670. These two pins are
simple switches to connect the status LED cath-
odes to ground. It is not necessary to use both dis-
play LEDs if a user simply wants to have a single
lamp to show "charging" or "not charging". This can
be accomplished by using the STAT1 pin and a sin-
gle LED. Using two LEDs and both STAT pins sim-
ply gives the user more information for the various
charging states. Refer to Table 4 for LED display
definitions.
The LED anodes should be connected to USB, ADP,
BAT, or OUT depending upon the system design
requirements. The LEDs should be biased with as
little current as necessary to create reasonable illu-
mination. A ballast resistor should be placed
between the status LED cathodes and the STAT1/2
pins. LED current consumption will add to the over
thermal power budget for the device package, hence
it is good reason to keep the LED drive current to a
minimum. 2mA should be sufficient to drive most
common low cost green or red LEDs. It is not rec-
AAT3670
1.6A Dynamic Battery Charger
and Power Manager
ommended to exceed 8mA for driving an individual
status LED. The required ballast resistor value can
be estimated using the following formulas:
For connection to the adapter supply:
Eq. 3:
R = B(STAT1/2)
(VADP - VF(LED))
ILED(STAT1/2)
Example: RB(STAT1) = (5.5V - 2.0V) 2mA = 1.75kΩ
Note: Red LED forward voltage (VF) is typically
2.0V @ 2mA.
For connection to the USB supply:
Eq. 4: RB(STAT1/2) =
(VUSB - VF(LED))
ILED(STAT1/2)
Example: RB(STAT2) = (5.0V - 3.2V) 2mA = 900Ω
Note: Green LED forward voltage (VF) is typically
3.2V @ 2mA.
For connection to the BAT supply:
Eq. 5: RB(STAT1/2) =
(VBAT - VF(LED))
ILED(STAT1/2)
Example: RB(STAT2) = (3.6V - 3.2V) 2mA = 200Ω
Note: Green LED forward voltage (VF) is typically
3.2V @ 2mA.
Event Description
End of Charge (TERM Current Reached in CVM), Battery OV, Timeout, or Charge Disabled
No Battery (With Charge Enabled)
Battery Charging (Including Suspended Charging Due to Battery OT/UT, or Device OT )
Event Description
Charge Disabled, No Battery, End of Charge, or Charging Without Faults
Faults (Battery OV/OT/UT, or Device OT) or Timeout
STAT1
OFF
Flash (1Hz, 40% duty)
ON
STAT2
OFF
ON
Table 4: LED Status Indicator (STATx Pulled Up to a Voltage Source with Resistors and LED).
28
3670.2007.02.1.1
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