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

X3100/X3101 – Preliminary Information
—Load Monitor (LMON)
In Over-current Protection mode, a small test current
(7.5µA typ.) is passed out of this pin to sense the load
resistance. The measured load resistance determines
whether or not the X3100 or X3101 returns from an
over-current protection mode (see section “Over-Current
Protection” on page 18).
Over-discharge (Under Voltage) Protection/
Over-current Protection (UVP/OCP):
Pin UVP/OCP controls the battery cell discharge via an
external power FET. This P-channel FET allows cell
discharge when UVP/OCP=Vss, and prevents cell
discharge when UVP/OCP=Vcc. The X3100 and X3101
turn the external power FET off when the X3100 or
X3101 detects either:
—Over-discharge Protection (UVP)
In this case, pin 24 is referred to as “Over-discharge
(Under-Voltage) protection (UVP)” (see section “Over-
discharge Protection” on page 15). UVP/OCP turns off
the FET to prevent damage to the battery cells by being
discharged to excessively low voltages.
—Over-current protection (OCP)
In this case, pin 24 is referred to as “Over-current
protection (OCP)” (see section “Over-Current Protection”
on page 18). UVP/OCP turns off the FET to prevent
damage to the battery pack caused by excessive current
drain (e.g. as in the case of a surge current resulting
from a stalled disk drive).
TYPICAL APPLICATION CIRCUIT
The X3100 and X3101 have been designed to operate
correctly when used as connected in the Typical
Application Circuit (see Figure 1 on page 5).
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_SS, and OFF when the gates are at
V_CC. As 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 X3100 or X3101 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.
The operation of the voltage regulator is described in
section “Voltage Regulator” on page 21. 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_RGO to
decay to 0.1V in 170ms or less when the X3100 or
X3101 enter 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_PUR + T_OC), V_RGO has
a stable, regulated output in the range of 5VDC ± 10%
(see Figure 2). The selection of the microcontroller
should take this into consideration. At the end of this turn
on period, the X3100 and X3101 “self-tunes” the output
of the voltage regulator to 5V+/-0.5%. As such, V_RGO
can be used as a reference voltage for the A/D converter
in the microcontroller. Repeated power up operations,
consistently re-apply the same “tuned” value for V_RGO.
Figure 1 shows a battery pack temperature sensor
implemented as a simple resistive voltage divider,
utilizing a thermistor (R_T) and resistor (R_T’). The voltage
V_T can be fed to the A/D input of a microcontroller and
used to measure and monitor the temperature of the
battery cells. R_T’ should be chosen with consideration of
the dynamic resistance range of R_T as well as the input
voltage range of the 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
Over-current protection mode (see section “Over-
Current Protection” on page 18), 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_PU is connected across the gate and drain of
the charge FET (Q2). The discharge FET Q1 is turned
off by the X3100 or X3101, 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_P+–V_D7). Since the drain of Q2 is
connected to a higher potential (V_P+) a pull-up resistor
REV 1.1.8 12/10/02
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Characteristics subject to change without notice. 4 of 40