AAT3686-3 Advanced Analog Technology, Inc., AAT3686-3 Datasheet - Page 14

• Manufacturer Part Number: AAT3686-3
• Description: USB Port/AC Adapter Lithium-Ion/Polymer Battery Charger
• Manufacturer: Advanced Analog Technology, Inc.

The USB charge reduction system becomes active when
the voltage on the USB input falls below the USB charge
reduction threshold (V
Regardless of which USB charge function is selected
(USBH or USBL), the charge reduction system will reduce
the fast charge current level in a linear fashion until the
voltage sensed on the USB input recovers above the
charge reduction threshold voltage. The USB charge
reduction threshold (V
value lower than 4.5V by placing a resistor divider net-
work between V
to the CHR pin. The USB charge reduction feature can be
14
BatteryManager
1000
1100
1200
1300
1400
1500
100
200
300
400
500
600
700
800
900
I
50
75
CC
Figure 2: Internal Equivalent Circuit
R11
R12
Table 1: Resistor Values.
USB
V
R
USB
SET
ADP
and ground with the center connected
84.5
43.2
28.0
21.0
16.9
13.3
11.5
10.2
9.09
8.06
7.32
6.65
6.04
5.36
for the CHR Pin.
N/A
N/A
5.62
CHR
(kΩ)
USBCHR
TM
USBCHR
) can be externally set to a
USB
), which is typically 4.5V.
R
825k
1.025M
SET
USBH
86.6
57.6
42.2
21.0
13.7
8.06
6.65
5.62
4.87
4.32
3.83
3.48
3.16
2.87
2.67
2.43
V
10.2
CHR
(kΩ)
= 2.0V
USB Port/AC Adapter Lithium-Ion/Polymer Battery Charger
R
SET
w w w . a n a l o g i c t e c h . c o m
USBL
86.6
57.6
42.2
20.5
13.7
10.2
8.06
6.65
5.62
4.87
4.32
3.83
3.48
3.16
2.87
2.67
2.43
(kΩ)
disabled by connecting a 10kΩ resistor from the CHR pin
directly to the USB input pin (see Figure 2).
The following equation can be used to approximate a
USB charge reduction threshold below 4.5V:
Where R11/R12 << 1MΩ.
USB Input Charge Inhibit and Resume
The AAT3686 UVLO and power on reset feature will func-
tion when the USB input pin voltage level drops below
the UVLO threshold. At this point, the charger will sus-
pend charging and shut down. When power is re-applied
to the USB pin or the UVLO condition recovers, the sys-
tem 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 AAT3686 provides an enable function to control the
charger IC on and off. The enable (EN) pin is active high.
When pulled to a logic low level, the AAT3686 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.
Programming Charge Current
The fast charge constant current charge level for both
adapter and USB input modes are programmed with set
resistors placed between the ADPSET, USBH, and USBL
pins 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, 1% tolerance metal film resistors are recom-
mended for the set resistor function.
Fast charge constant current levels from 50mA to 1.5A
can be set by selecting the appropriate resistor value
from Table 1. The R
between the ADPSET pin and ground.
The USB input fast charge constant current charge control
provides for two current set levels, USBH and USBL. The
USBSEL pin is used to select the high or low charge cur-
rent levels in the USB charge mode. When the USBSEL pin
V
USBCHR
PRODUCT DATASHEET
= 2.0V ÷
SET
resistor should be connected
AAT3686
R12 + R11
R12
3686.2007.12.1.11