AAT3670 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT3670' PDF : 32 Pages View PDF
minal will be close to 0Ω; if the BATS connection
becomes an open circuit, the 10Ω will provide feed-
back to the BATS pin from the BAT connection will a
1mV or less loss in sensed voltage accuracy.
Enable
The AAT3670 provides an enable function to con-
trol the charger IC on and off. The enable (EN) pin
is active high. When pulled to a logic low level, the
AAT3670 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.
Battery Enable
Since the AAT3670 provides battery power switching
as well as charging function, a battery enable pin
(ENBAT) is provided so the power from the battery via
the BAT pin to the OUT pin may be externally con-
trolled. The ENBAT function allows the user to control
power to the systems regardless of charging state,
input power source, or charge enable (EN) state.
It may be desirable for some system designs to dis-
connect the battery from the load during charging.
This may be accomplished by pulling the ENBAT
pin low, while the device is enabled for charging
(EN high).
Programming Charge Current
The fast charge constant current charge level for
both adapter and USB input modes are pro-
grammed with set resistors placed between the
ADPSET or USBSET pins and ground. The accu-
racy of the fast charge constant current and the
preconditioning trickle charge current are dominat-
ed by the tolerance of the set resistor used. For
this reason, 1% tolerance metal film resistors are
recommended for this set resistor function.
Fast charge constant current levels from 50mA to
1.6A may be set by selecting the appropriate resis-
tor value from Table 2. The RADPSET resistor should
be connected between the ADPSET pin and ground.
The USB input fast charge constant current charge
control provides up to 900mA of charge current and
is set in the USBH mode. The USBSEL pin is used
to select the high or low charge current levels in the
24
AAT3670
1.6A Dynamic Battery Charger
and Power Manager
USB charge mode. When the USBSEL pin is pulled
to a voltage level above the VUSBSEL(H) threshold, the
USBH current level will be selected. Conversely, this
pin should be pulled below the VUSBSEL(L) threshold
to enable the USBL charge level; the USBL charge
current will be set to 20% of the set USBH level. For
typical USB charging applications, the USBH and
USBL functions are fixed for 500mA and 100mA
USB fast charge levels. However, the charge level of
USBH may be set from 50mA to 900mA and USBL
will in turn be fixed at 20% of the USBH level
depending upon the system design requirements for
a given USB charge application. Refer to Table 2
and Figure 4 for recommended RUSBSET values.
(mICAC )
50
90
100
150
200
250
300
400
500
650
800
900
1000
1200
1500
1600
ADP
RSET (kΩ)
1300
681
590
412
309
249
205
154
121
93.1
73.2
64.9
57.6
48.7
38.3
34.8
USBH
RSET (kΩ)
750
453
383
249
187
150
124
90.9
71.5
54.9
43.2
38.3
USBL
RSET (kΩ)
150
80.6
71.5
47.5
34.8
Table 2: RSET Values.
1800
1600
1400
1200
1000 USBH
800
600 USBL
400
200
0
10
ADP
100
1000
RSET (kΩ)
10000
Figure 4: Fast Charge Current vs. Set Resistor
(VIN = 5V; VBAT = 3.5V).
3670.2007.02.1.1
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