EUP8020X
Functional Description
Autonomous Power Source Selection
As default the EUP8020X attempts to charge from the
AC input. If AC input is not present, the USB is selected.
If both inputs are available, the AC adapter has the
priority. See Figure 4 for details.
The EUP8020X activates a safety timer, t
(PRECHG)
, during
the conditioning phase. If V
(LOWV)
threshold is not
reached within the timer period, the EUP8020X turns off
the charger and enunciates FAULT on the STATx pins.
Please refer to the Timer Fault Recovery section for
additional details.
Figure 4.Typcial Charging Profile
Temperature Qualification
( 8020A,8020D,8020E,8020F,8020G Only)
The EUP8020X continuously monitors battery
temperature by measuring the voltage between the TS
and VSS pins.
An internal current source provides the bias for most
common 10-kΩ negative-temperature coefficient
thermistors (NTC) (see Figure 5). The device compares
the voltage on the TS pin against the internal V
(LTF)
and
V
(HTF)
thresholds to determine if charging is allowed.
Once a temperature outside the V
(LTF)
and V
(HTF)
thresholds is detected the device immediately suspend the
charge. The device suspend charge by turning off the
power FET and holding the timer value (i.e. timers are
NOT reset). Charge is resumed when the temperature
returns to the normal range.
However the user may modify these thresholds by adding
two external resistors. See Figure 6.
Battery Pre-Conditioning
During a charge cycle if the battery voltage is below the
V
(LOWV)
threshold, the EUP8020X applies a precharge
current, I
O(PRECHG)
, to the battery. This feature revives
deeply discharged cells. The resistor connected between
the ISET1 and V
SS
, R
SET
, determines the precharge rate.
The V
(PRECHG)
and K
(SET)
parameters are specified in the
specifications table. Note that this applies to both AC and
USB charging.
I
O(PRECHG)
=
V(PRECGH )
×
K (SET )
R SET
Figure 5. Temperature Sensing Configuration
Figure 6. Temperature Sensing Thresholds
Battery Charge Current
The EUP8020X offers on-chip current regulation with
programmable set point. The resistor connected between
the ISET1 and V
SS
, R
SET
, determines the AC charge rate.
The V
(SET)
and K
(SET)
parameters are specified in the
specifications table.
V(SET )
×
K (SET )
R SET
I
O(OUT)
=
----------------------
(2)
------------
(1)
When charging from a USB port, the host controller has
the option of selecting either 100 mA or 500 mA charge
rate using ISET2 pin. A low-level signal sets current at
100 mA and a high level signal sets current at 500 mA. A
high-Z input disables USB charging.
DS8020X Ver 1.1 June 2006
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
