EUP8051A
Qualification and Precharge
When power is applied, the EUP8051A 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 EUP8051A 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 EUP8051A also checks the
battery voltage. If the battery voltage is below the
precharge threshold V(min), the EUP8051A 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 EUP8051A monitors the battery-pack
voltage between the BAT and VSS pins. The EUP8051A
is offered in two fixed-voltage versions: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
EUP8051A, 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 EUP8051A regulates current while the battery-pack
voltage is less than the regulation voltage, VO(REG). The
EUP8051A 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
DS8051A Ver 1.1 Nov. 2006
11