AAT3684 Datasheet, PDF (11/17 Pages) Advanced Analogic Technologies – 500mA USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger

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PRODUCT DATASHEET
AAT3684
500mA USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger
Application Information
Adapter or USB Power Input
Constant current charge levels up to 500mA may be
programmed by the user when powered from a sufficient
input power source. The AAT3684 will operate from the
adapter input over a 4.0V to 6.5V range. The constant
current fast charge current for the adapter input is set
by the R_SET resistor connected between ISET and ground.
Refer to Table 1 for recommended R_SET values for a
desired constant current charge level.
Adapter Input Charge Inhibit and Resume
The AAT3684 has a UVLO and power on reset feature so
that if the input supply to the ADP pin drops below the
UVLO threshold, the charger will suspend charging and
shut down. When power is re-applied to the ADP pin or
the UVLO condition recovers, the system charge control
will assess the state of charge on the battery cell and will
automatically resume charging in the appropriate mode
for the condition of the battery.
Enable / Disable
The AAT3684 provides an enable function to control the
charger IC on and off. The enable (EN) pin is internally
pulled down. When pulled to a logic high level, AAT3684
is enabled. When left open or pulled to a logic low level,
the AAT3684 will be shut down and forced into the sleep
state. Charging will be halted regardless of the battery
voltage or charging state. When the device is re-enabled,
the charge control circuit will automatically reset and
resume charging functions with the appropriate charging
mode based on the battery charge state and measured
cell voltage on the BAT pin.
Programming Charge Current
The fast charge constant current charge level is user
programmed with a set resistor placed between the ISET
pin and ground. The accuracy of the fast charge, as well
as the preconditioning trickle charge current, is domi-
nated by the tolerance of the set resistor used. For this
reason, a 1% tolerance metal film resistor is recom-
mended for the set resistor function. Fast charge con-
stant current levels from 15mA to 500mA may be set by
selecting the appropriate resistor value from Table 1.
Nominal
I_CHARGE (mA)
500
450
400
350
300
250
200
150
100
50
40
30
20
15
Set Resistor
Value (kΩ)
3.24
3.57
4.12
4.64
5.36
6.49
8.06
10.7
16.2
31.6
38.3
53.6
78.7
105
Table 1: R_SET Values.
1000
100
10
1
1
10
100
1000
R_SET (kΩ)
Figure 2: Constant Charging Current
vs. Set Resistor Values.
Protection Circuitry
Over-Voltage Protection
An over-voltage event is defined as a condition where
the voltage on the BAT pin exceeds the maximum bat-
tery charge voltage and is set by the over-voltage pro-
tection threshold (V_OVP). If an over-voltage condition
occurs, the AAT3684 charge control will shut down the
device until voltage on the BAT pin drops below V_OVP. The
AAT3684 will resume normal charging operation after
the over-voltage condition is removed.
3684.2007.12.1.2
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