Diodes AUR9807 - Manual (Page 17)

Data Sheet
Single-cell Li-Ion Charger IC with System Power Management AUR9807
Nov. 2011 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
17
NTC
Li Battery
1µF
BAT
TS
V
LTF
V
HTF
100µA
AUR9807
LO
G
IC UN
IT
Charge Function Descriptions (Continued)
Active Power Management (APM)
„ AC MODE (MODE=HIGH)
i. V
APM-REG OUT
: Normal Mode; I
CHG
determined
by R
SET
ii. V
BAT OUT APM-REG
: APM mode ; I
CHG
= I
supply
max
–I
OUT
iii. V
OUT BAT
: BAT supply mode
„
USB 500 MODE (MODE=LOW ,
ISET2=HIGH)
i. V
APM-REG OUT
: Normal Mode; I
CHG
determined
by R
SET
ii. V
BAT OUT APM-REG
: APM mode; I
CHG
=
450mA – I
OUT
iii. V
OUT BAT
: BAT supply mode
„
USB 100 MODE (MODE=LOW ,
ISET2=LOW)
i. V
APM-REG OUT
: Normal Mode; I
CHG
determined
by R
SET
ii. V
BAT OUT APM-REG
: APM mode; I
CHG
=
90mA–I
OUT
iii. V
OUT BAT
: BAT supply mode
The active power management feature adjusts the
charging current to resist the output voltage drop due to
heavy system loading or insufficient input driving
capability. In the extreme situation, the charging current
flow would be reversed (the battery helps to supply the
system power). The active power management
regulation voltage V
APM-REG
is given by:
V
APM-REG
= I
APM-SET
×R
APM
× SF (4)
When the output voltage is higher than V
APM-REG
, the
input source is capable of providing the charging
current (set by R
SET
) and output current (determined by
system loading) simultaneously. When the output
voltage goes down and reaches V
APM-REG
due to an
increasing loading, AUR9807 starts to reduce the
charging current and tries to keep the output voltage at
V
APM-REG
. Because AUR9807 uses the remaining
available current to charge the battery, the charging
current can be estimated as I
supply max
– I
OUT
. In AC mode,
the I
supply max
is determined by the driving capability of
the AC adapter and AUR9807 itself (usually the
limiting factor is the AUR9807, and I
supply max
is about
2A). The I
supply max
is determined by the ISET2 setting in
USB mode (I
supply max
is about 450mA with ISET2 high,
and I
supply max
is about 90mA with ISET2 low).
When the loading current keeps increasing and exceeds
I
supply max
, the AUR9807 can not prevent the output
voltage dropping below V
APM-REG
even the charging
current is reduced to zero. When the output voltage
drops below the battery voltage, the battery helps to
supply the loading current and keeps the output voltage
roughly at V
BAT
. At this situation, we have:
I
OUT
= I
supply max
+I
BAT
(5)
(4) R
APM
<38kΩ: V
APM-REG
=I
APM-SET
×R
APM
×SF
R
APM
>41kΩ: The V
APM-REG
is set to a
predetermined fixed value (4.26V)
(5) I
BAT
=(V
BAT
–V
OUT
) / (40mΩ Power Path
Resistance)
Battery Temperature Protection