AAT3670 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT3670' PDF : 32 Pages View PDF
If the programmable watchdog timer function is not
needed it may be disabled the terminating the CT
pin to ground. The CT pin should not be left float-
ing or un-terminated; this will cause errors in the
internal timing control circuit.
The charge timer control will suspend the timing
count in any given mode in the event a fault condi-
tion occurs. Such fault conditions include digital
thermal loop charge current reduction, ADP or USB
charge reduction, battery temperature fault, and
battery current sharing with the output during the
charging cycle. When the fault condition recovers,
the counter will resume the timing function. The
charge timer will automatically reset when the
AAT3670 enable pin is reset or cycled off and on.
The constant current provided to charge the timing
capacitor is very small and this pin is susceptible to
noise and changes in capacitance value.
Therefore, the timing capacitor should be physical-
ly located on the printed circuit board layout as
close as possible to the CT pin. Since the accura-
cy of the internal timer is determined by the capac-
itance value, a 10% tolerance or better ceramic
capacitor is recommended. Ceramic capacitor
materials such as X7R and X5R type are a good
choice for this application.
Over-Current Protection
The AAT3670 provides over-current protection to
both the battery and system output modes for both
the ADP and USB input sources.
The over-current protection threshold is user pro-
grammable and independent from the constant
charge current setting. The set resistor RADPLIM is
connected between the ADPLIM pin and ground to
program the ADP power path current limit up to
1.6A. The set resistor RUSBLIM is connected
between the USBLIM pin and ground to program
the USB power path current limit up to 900mA. For
both the ADP and USB charge paths, the pro-
grammed constant current fast charge level may
not exceed the respective ADPLIM and USBLIM
set points. Refer to Table 3 for the ADPLIM and
USBLIM programming resistor values.
AAT3670
1.6A Dynamic Battery Charger
and Power Manager
ICC (mA)
50
90
100
150
200
250
300
400
500
650
800
900
1000
1200
1500
1600
RADPLIM (kΩ)
1300
681
590
412
309
249
205
154
121
93.1
73.2
64.9
57.6
48.7
38.3
34.8
RUSBLIM (kΩ)
750
453
383
249
187
150
124
90.9
71.5
54.9
43.2
38.3
Table 3: Current Limit Programming
Resistor Values.
If the desired charge current limit level is not listed in
Table 3, the ADPLIM and USBLIM set resistor val-
ues may be calculated by the following equations:
For the Adapter input mode:
Where:
RADPLIM = K ·
⎛ VADPLIM⎞
⎝ ICC ⎠
K
= KI_LIM_ADP = 27800
VADPLIM = 2V
ICC = Fast Charge Constant Current
For the USB input mode:
Where:
RUSBLIM = K ·
⎛ VUSBLIM⎞
⎝ ICC ⎠
K
= KI_LIM_USBH = 17600 (USBH)
K
= KI_LIM_USBL = 3500 (USBL)
VUSBLIM = 2V
ICC = Fast Charge Constant Current
26
3670.2007.02.1.1
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