X3100-01 Datasheet, PDF (16/41 Pages) Intersil Corporation – Cell Balancing Control

X3100, X3101
Over-discharge Protection
If V_CELL < V_UV, for a time exceeding T_UV, the cells are
said to be in a over-discharge state (Figure 4). In this
instance, the X3100 and X3101 automatically switch
the discharge FET OFF (UVP/OCP = Vcc), and then
enter sleep mode.
The over-discharge (under-voltage) value, V_UV, can be
selected from the values shown in Table 5 by setting
bits VUV1, VUV0 in the configuration register. These
bits are set using the WCFIG command. Once in the
sleep mode, the following steps must occur before the
X3100 or X3101 allows the battery cells to discharge:
– The X3100 and X3101 must wake from sleep mode
(see section “Voltage Regulator” on page 22).
– The charge FET must be switched ON by the micro-
controller (OVP/LMON=V_SS), via the control register
(see section “Control Register Functionality” on
page 11).
– All battery cells must satisfy the condition: V_CELL >
V_UVR for a time exceeding T_UVR.
– The discharge FET must be switched ON by the
microcontroller (UVP/OCP=V_SS), via the control reg-
ister (see section “Control Register Functionality” on
page 11)
The times T_UV/T_UVR are varied using a capacitor (C_UV)
connected between pin UVT and GND (Table 13). The
delay T_UV that results from a particular capacitance C_UV,
can be approximated by the following linear equation:
T_UV (s) ≈ 10 x C_UV (µF)
T_UVR (ms) ≈ 70 x C_UV (µF)
Table 21. Typical Over-discharge Delay Times
Symbol
T_UV
T_UVR
Description
Over-discharge
detection delay
Over-discharge
release time
C_UV
0.1µF
Delay
1.0s (Typ)
0.1µF 7ms (Typ)
Sleep Mode
The X3100 or X3101 can enter sleep mode in two
ways:
i) The device enters the over-discharge protection
mode.
ii) The user sends the device into sleep mode using the
control register.
A sleep mode can be induced by the user, by setting
the SLP bit in the control register (Table 13) using the
WCNTR Instruction.
In sleep mode, power to all internal circuitry is
switched off, minimizing the current drawn by the
device to 1µA (max). In this state, the discharge FET
and the charge FET are switched OFF
(OVP/LMON=V_CC and UVP/OCP=V_CC), and the 5VDC
regulated output (V_RGO) is 0V. Control of UVP/OCP
and OVP/LMON via bits UVPC and OVPC in the con-
trol register is also prohibited.
The device returns from sleep mode when V_CC ≥ V_SLR.
(e.g. when the battery terminals are connected to a
battery charger). In this case, the X3100 or the X3101
restores the 5VDC regulated output (section “Voltage
Regulator” on page 22), and communication via the
SPI port resumes.
If the Cell Charge Enable function is enabled when
V_CC rises above V_SLR, the X3100 and X3101 internally
verifies that the individual battery cell voltages (V_CELL)
are larger than the cell charge enable voltage (V_CE)
before allowing the FETs to be turned on. The value
of V_CE is selected by using the WCFIG command to
set bits VCE1–VCE0 in the configuration register.
Only if the condition “V_CELL > V_CE” is satisfied can
the state of charge and discharge FETs be changed
via the control register. Otherwise, if V_CELL < V_CE for
any battery cell then both the Charge FET and the dis-
charge FET are OFF (OVP/LMON=Vcc and
UVP/OCP=V_CC). Thus both charge and discharge of
the battery cells via terminals P+ / P- is prohibited¹.
The cell charging threshold function can be switched
ON or OFF by the user, by setting bit SWCEN in the
configuration register (Table 7) using the WCFIG com-
mand. In the case that this cell charge enable function
is switched OFF, then V_CE is effectively set to 0V.
Neither the X3100 nor the X3101 enter sleep mode
(automatically or manually, by setting the SLP bit) if
V_CC ≥ V_SLR. This is to ensure that the device does not
go into a sleep mode while the battery cells are at a
high voltage (e.g. during cell charging).
1. In this case, charging of the battery may resume ONLY if the
cell charge enable function is switched OFF by setting bit
SWCEN = 1 in the configuration register (See Above,
“CONFIGURATION REGISTER FUNCTIONALITY” on
page 9).
16
FN8110.1
January 3, 2008