X3100 Datasheet, PDF (14/40 Pages) Xicor Inc. – 3 or 4 Cell Li-Ion Battery Protection and Monitor IC

X3100, X3101
Over-charge Protection
The X3100 and X3101 monitor the voltage on each
battery cell (V_CELL). If for any cell, V_CELL > V_OV for a
time exceeding T_OV, then the Charge FET will be
switched OFF (OVP/LMON = V_CC). The device has
now entered Over-charge protection mode (Figure 5).
The status of the discharge FET (via pin UVP) will
remain unaffected.
While in over-charge protection mode, it is possible to
change the state of the OVPC bit in the control register
such that OVP/LMON = Vss (Charge FET = ON).
Although the OVPC bit in the control register can be
changed, the change will not be seen at pin OVP until
the X3100 or X3101 returns from over-charge protec-
tion mode.
The over-charge detection delay T_OV, is varied using a
capacitor (C_OV) connected between pin OVT and
GND. A typical delay time is shown in Table 10. The
delay T_OV that results from a particular capacitance
C_OV, can be approximated by the following linear
equation:
T_OV (s) ≈ 10 x C_OV (µF).
Table 19. Typical over-charge detection time
Symbol
T_OV
C_OV
0.1µF
Delay
1.0s (Typ)
The device further continues to monitor the battery cell
voltages, and is released from over-charge protection
mode when V_CELL< V_OVR, for all cells. When the
X3100 or X3101 is released from over-charge protec-
tion mode, the charge FET is automatically switched
ON (OVP/LMON = V_SS). When the device returns from
over-charge protection mode, the status of the dis-
charge FET (pin UVP/OCP) remains unaffected.
The value of V_OV can be selected from the values
shown in Table 4 by setting bits VOV1, VOV0. These
bits are set by using the WCFIG instruction to write to
the configuration register.
Figure 5. Over-charge Protection Mode—Event Diagram
Normal Operation Mode
V_CELL
T_OV
OVP/LMON
Over-charge
Protection
Mode
Normal Operation Mode
V_OV
V_OVR
V_CC
V_SS
Event
0
1
2
3
14
FN8110.0
April 11, 2005