ACT5880
Rev 2, 03-Sep-13
RDDW is 220kꢀ. The input of an adaptor in
compliance with the "Battery Charging" and the
"YD/T1591" specifications is identified if both the
CHGIN and the ACIN are read valid. Only the
CHGIN read valid is for USB host attached or for
hub attached, while only the ACIN read valid is for
USB OTG A-device attached or for an over-loaded
weak adaptor attached. The resistive detection
provides reliable detection in most cases but the
case of a USB OTG A-device powering the VBUS
with its local 5V, which is a known operation state of
the device. The RDUP and the RISO should be placed
close to the traces connecting the USB receptacle
pins and USB PHY pins, for less branching effect,
which is important to running high speed
transmission.
Figure 19:
The Charge and Discharge Curves for NiMH
Cell.
1.6V
1.4V
1.2V
1C
0.33C
0.1C
Charge Curve at 25˚C
80% 100%120%
1.6V
1.4V
1.2V
40˚C
20˚C
0˚C
Charge Curve at 1C charge
80% 100%120%
1.4V
1.2V
1.0V
Figure 20:
The Sample Circuit for USB Charging.
0.2C discharge at 25˚C
VBUS
VBUS
1C
1.8C
D-
D+
Device
USB I/F
Long Cord Power Operation
Foreign
Adaptor
or USB
RISO
When a device whose normal operation is with a
power cord connected, the charger may frequently
seesaw charges the battery. Programming the fast
charge current to a smaller volume could have the
end of charge current less than the operation
current and then the end of charge condition does
not happen, forces the charger into floating. The
floating state causes less aging than the frequent
seesaw charge does. For staying in floating, the
total charge time-out function should be disabled
and the battery regulation should be programmed to
100mV lower than the nominal battery charge
termination voltage, which is desired for safe
floating and enlarges the battery life cycles.
USB connectors
RDUP
ACIN
RDDW
CHGIN
ACT5880
When a suitable voltage power applied on the
CHGIN, and while charging function allowed
(SUSCHG=0), if no battery detected, the charger
path turns into the LDO mode, in which it regulates
the VBAT voltage to power the system. The system
defines its way of operation in no-battery situation,
either as a no-battery USB device or turns its self
into device suspend mode with less than 2.5mA
drawn from USB port. In the LDO mode, the output
voltage is set by the VSET[ ], the pass current is
limited to the fast charge current set as a function of
the ISET[ ] and the CHGLEV, and the charge timers
are cleared. The thermal regulation keeps
preventing the die from overheating.
USB Charging
The ACT5880 provides the adaptor charge input
detection, the battery installed detection, the
CHGLEV charge current set input and with few
programmable registers for the USB charging. 3
situations in battery powered devices specified in
the "Battery Charging" specification of the USB IF
are supported, the no-battery situation, the
weak/dead battery situation and the battery normal
situation. Specified device behavior in those
situations is required only if the power source is
identified as a host charger or a hub charger.
When a USB or a hub is attached while the device
is with a weak/dead battery from the device system
point of view, while the charging function is default
enabled (SUSCHG=0), the ACT5880 starts
charging with the fast charge set by the CHGLEV or
precondition charges the battery, dependent on if
the battery voltage is greater or less than the
precondition threshold. The CHGLEV should be
connected to an I/O of the host system with a pull-
down resistor around 1Mꢀ. Before the processor
The ACT5880 deploys the resistive method
recommended by the USB IF for the power source
identification, with its precise threshold ACIN input.
Ref to the Figure 20, a sample circuit uses single
port for both USB connection and charging, in
which the RDUP is 220kꢀ, the RISO is 240kꢀ and the
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