x3102v28 Intersil Corporation, x3102v28 Datasheet - Page 11

• Manufacturer Part Number: x3102v28
• Description: 3 Cell Li-ion Battery Protection And Monitor Ic
• Manufacturer: Intersil Corporation

Principles of Operation
The X3102 provides two distinct levels of functionality and
battery cell protection:
First, in Normal mode, the device periodically checks each
cell for an over-charge and over-discharge state, while
continuously watching for a pack overcurrent condition. A
protection mode violation results from an over-charge, over-
discharge, or overcurrent state. The thresholds for these
states are selected by the user through software. When one
of these conditions occur, a Discharge FET or a Charge FET
or both FETs are turned off to protect the battery pack. In an
over-discharge condition, the X3102 device goes into a low
power sleep mode to conserve battery power. During sleep,
the voltage regulator turns off, removing power from the
microcontroller to further reduce pack current.
Second, in Monitor mode, a microcontroller with A/D converter
measures battery cell voltage and pack current via pin AO
and the X3102 on-board MUX. The user can thus implement
protection, charge/discharge, cell balancing or gas gauge
software algorithms to suit the specific application and
characteristics of the cells used. While monitoring these
voltages, all protection circuits are on continuously.
In a typical application, the microcontroller is also
programmed to provide an SMBus interface along with the
Smart Battery System interface protocols. These additions
allow an X3102 based module to adhere to the latest
industry battery pack standards.
Typical Application Circuit
The X3102 has been designed to operate correctly when
used as connected in the Typical Application Circuit (See
Figure 7).
The power MOSFET’s Q1 and Q2 are referred to as the
“Discharge FET” and “Charge FET,” respectively. Since
these FETs are p-channel devices, they will be ON when the
gates are at V
their names imply, the discharge FET is used to control cell
discharge, while the charge FET is used to control cell
charge. Diode D1 allows the battery cells to receive charge
even if the Discharge FET is OFF, while diode D2 allows the
cells to discharge even if the charge FET is OFF. D1 and D2
are integral to the Power FETs. It should be noted that the
cells can neither charge nor discharge if both the charge FET
and discharge FET are OFF.
Power to the X3102 is applied to pin VCC via diodes D6 and
D7. These diodes allow the device to be powered by the
Li-Ion battery cells in normal operating conditions, and allow
the device to be powered by an external source (such as a
charger) via pin P+ when the battery cells are being
charged. These diodes should have sufficient current and
voltage ratings to handle both cases of battery cell charge
and discharge.
SS
, and OFF when the gates are at V
11
CC
. As
X3102
The operation of the voltage regulator is described in section
“Voltage Regulator” on page 26. This regulator provides a
5VDC±0.5% output. The capacitor (C1) connected from
RGO to ground provides some noise filtering on the RGO
output. The recommended value is 0.1µF or less. The value
chosen must allow V
when the X3102 enters the sleep mode. If the decay is
slower than this, a resistor (R1) can be placed in parallel with
the capacitor.
During an initial turn-on period (T
stable, regulated output in the range of 5VDC ± 10% (See
Figure 8). The selection of the microcontroller should take
this into consideration. At the end of this turn on period, the
X3102 “self-tunes” the output of the voltage regulator to
5V±0.5%. As such, V
voltage for the A/D converter in the microcontroller.
Repeated power up operations, consistently re-apply the
same “tuned” value for V
Figure 1 shows a battery pack temperature sensor
implemented as a simple resistive voltage divider, utilizing a
thermistor (R
to the A/D input of a microcontroller and used to measure
and monitor the temperature of the battery cells. R
be chosen with consideration of the dynamic resistance
range of R
microcontroller A/D input. An output of the microcontroller
can be used to turn on the thermistor divider to allow
periodic turn-on of the sensor. This reduces power
consumption since the resistor string is not always drawing
current.
Diode D3 is included to facilitate load monitoring in an
overcurrent protection mode (See section “Overcurrent
Protection” on page 23), while preventing the flow of current
into pin OVP/LMON during normal operation. The
N-Channel transistor turns off this function during the sleep
mode.
Resistor R
charge FET (Q2). The discharge FET Q1 is turned off by the
X3102, and hence the voltage at pin OVP/LMON will be (at
maximum) equal to the voltage of the battery terminal, minus
one forward biased diode voltage drop (V
drain of Q2 is connected to a higher potential (V
resistor (R
that the charge FET is completely turned OFF when
OVP/LMON = V
PU
T
PU
as well as the input voltage range of the
) in the order of 1M:
T
is connected across the gate and drain of the
) and resistor (R
CC
.
RGO
RGO
RGO
to decay to 0.1V in 170ms or less
can be used as a reference
.
T
’). The voltage V

PUR
should be used to ensure
+ T
P+
OC
–V
), V
D7
P+
December 22, 2004
). Since the
T
RGO
) a pull-up
can be fed
T
’ should
has a
FN8246.0