X3100 Datasheet, PDF (21/40 Pages) Xicor Inc. – 3 or 4 Cell Li-Ion Battery Protection and Monitor IC

X3100/X3101 – Preliminary Information
of four input resistors to Op Amp OP1. The feedback
resistors remain constant. This ratio of input to feedback
resistors determines the gain. Putting external resistors
in series with the inputs reduces the gain of the amplifier.
VCS1 and VCS2 are read at AO with respect to a DC
bias voltage of 2.5V. Therefore, the voltage range of
VCS₁₂ and VCS₂₁ changes depending upon the
direction of current flow (i.e. battery cells are in Charge
or Discharge—Table 21).
Table 26. AO Voltage Range for VCS₁₂ and VCS₂₁
AO
Cell State
AO Voltage Range
VCS₁₂
VCS₁₂
VCS₂₁
VCS₂₁
Charge
Discharge
Charge
Discharge
2.5V ≤ AO ≤ 5.0V
0V ≤ AO ≤ 2.5V
0V ≤ AO ≤ 2.5V
2.5V ≤ AO ≤ 5.0V
By calculating the difference of VCS₁₂ and VCS₂₁ the
offset voltage of the internal op-amp circuitry is
cancelled. This allows for the accurate calculation of
current flow into and out of the battery cells.
Pack current is calculated using the following formula:
Pack Current = ₍---2----₎--₍--g----a---i--n-----s---e--⁽-t-V-t-i--n-C--g--S--₎--(¹--c-²--u--^–-r--r--Ve----nC---t--S-s---²_e---¹-n--⁾-s---e-----r--e----s---i-s---t--o---r--)
VOLTAGE REGULATOR
The X3100 and X3101 are able to supply peripheral
devices with a regulated 5VDC±0.5% output at pin
RGO. The voltage regulator should be configured
externally as shown in Figure 10.
The non-inverting input of OP1 is fed with a high
precision 5VDC supply. The voltage at the output of the
voltage regulator (V_RGO) is compared to this 5V
reference via the inverting input of OP1. The output of
OP1 in turn drives the regulator pnp transistor (Q1). The
negative feedback at the regulator output maintains the
voltage at 5VDC±0.5% (including ripple) despite
changes in load, and differences in regulator transistors.
When power is applied to pin VCC of the X3100 or
X3101, V_RGO is regulated to 5VDC±10% for a nominal
time of T_OC+2ms. During this time period, V_RGO is
“tuned” to attain a final value of 5VDC±0.5% (Figure 2).
The maximum current that can flow from the voltage
regulator (I_LMT) is controlled by the current limiting
resistor (R_LMT) connected between RGP and VCC. When
the voltage across VCC and RGP reaches a nominal
2.5V (i.e. the threshold voltage for the FET), Q2 switches
ON, shorting VCC to the base of Q1. Since the base
voltage of Q1 is now higher than the emitter voltage, Q1
switches OFF, and hence the supply current goes to zero.
Typical values for R_LMT and I_LMT are shown in Table 27.
In order to protect the voltage regulator circuitry from
damage in case of a short-circuit, R_LMT ≥ 10Ω should
always be used.
Table 27. Typical Values for R_LMT and I_LMT
R_LMT
10Ω
Voltage Regulator Current Limit (I_LMT)
250mA ± 50% (Typical)
25Ω
100mA ± 50% (Typical)
50Ω
50mA ± 50% (Typical)
When choosing the value of R_LMT, the drive limitations
of the PNP transistor used should also be taken into
consideration. The transistor should have a gain of at
least 100 to support an output current of 250mA.
Figure 10. Voltage Regulator Operation
To Internal Voltage
Regulating Circuitry
VCC
X3100/X3101
Tuning
Q2
RGP
5VDC
Precision
Voltage
Reference
+
_
OP1
RGC
RGO
Un-Regulated
Voltage
Input
R_LMT
I_LMT
Q1
Regulated
5VDC Output
0.1 ^VRGO
µF
4KBIT EEPROM MEMORY
The X3100 and X3101 contain a CMOS 4k-bit serial
EEPROM, internally organized as 512 x 8 bits. This
memory is accessible via the SPI port, and features the
IDLock function.
The 4kbit EEPROM array can be accessed by the SPI
port at any time, even during a protection mode, except
during sleep mode. After power is applied to VCC of the
X3100 or X3101, EEREAD and EEWRITE Instructions
REV 1.1.8 12/10/02
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Characteristics subject to change without notice. 21 of 40