EUP8051
Qualification and Precharge
When power is applied, the EUP8051 starts
a
charge-cycle if a battery is already present or when a
battery is inserted. Charge qualification is based on
battery temperature and voltage.
The EUP8051 suspends charge if the battery temperature
is outside the V(TS1) to V(TS2) range and suspends charge
until the battery temperature is within the allowed range.
The EUP8051 also checks the battery voltage. If the
battery voltage is below the precharge threshold V(min),
the EUP8051 uses precharge to condition the battery. The
conditioning charge rate I(PRECHG) is set at approximately
10% of the regulation current. The conditioning current
also minimizes heat dissipation in the external
pass-element during the initial stage of charge. See
Figure5 for a typical charge-profile.
VoltageRegulation Phase
The voltage regulation feedback is through the BAT pin.
This input is tied directly to the positive side of the
battery pack. The EUP8051 monitors the battery-pack
voltage between the BAT and VSS pins. The EUP8051 is
offered in two fixed-voltage versions:4.1V, 4.2V.
FB/CE Pin Function
This pin has two functions, one is to enable/disable the
charge function, and the other is to finely adjust battery
regulation voltage. Connect this pin to VDD to enable
EUP8051, and connect to ground to disable it (Figure7).
If this pin is connected to a voltage divider as shown in
Figure8, it can be a 2.15V reference voltage to adjust the
output regulation voltage as desired.
Current Regulation Phase
The EUP8051 regulates current while the battery-pack
voltage is less than the regulation voltage, VO(REG). The
EUP8051 monitors charge current at the SNS input by
the voltage drop across a sense-resistor, RSNS, in series
with the battery pack. In current sensing configuration
(Figure6), RSNS is between the VCC and SNS pins,
charge-current feedback, applied through pin SNS,
maintains a voltage of V(SNS) across the current sense
resistor. The following formula calculates the value of the
sense resistor:
V
(SNS)
R
=
---------------------------- (1)
SNS
I
O(REG)
Where IO(REG) is the desired charging current.
Example: For 0.55A, RSNS: 0.22V/0.55A: 0.4Ω
For 1.0A, RSNS: 0.22V/1.0A: 0.22Ω
DS8051 Ver 1.6 Sep. 2006
11
EUTECH [ EUTECH MICROELECTRONICS INC ]
