x3102v28 Intersil Corporation, x3102v28 Datasheet - Page 25

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

Monitor Mode
Analog Multiplexer Selection
The X3102 can be used to externally monitor individual
battery cell voltages, and battery current. Each quantity can
be monitored at the analog output pin (AO), and is selected
using the analog select (AS0–AS2) pins (Table 25). Also,
see Figure 15.
NOTES:
Current Monitor Function
The voltages monitored at pins
used to calculate current flowing through the battery
terminals, using an off-board microcontroller with an A/D.
Since the value of the sense resistor (R
(typically in the order of tens of m:
of various A/D converters may vary, the voltage across
R
of between 10 and 160, and output to pin AO (Figure 15).
1. This is the normal state of the X3102. While in this state Over-
2. VCS
SENSE
AS2
H
H
H
H
L
L
L
L
charge and Over-discharge Protection conditions are
periodically monitored (See “Periodic Protection Monitoring” on
page 19.)
2.5V (See section “Current Monitor Function” on page 25).
1
, VCS
(
AS1
VCS
H
H
H
H
L
L
L
L
2
1
TABLE 25. AO SELECTION MAP
are read at AO with respect to a DC bias voltage of
AS0
and VCS
H
H
H
H
L
L
L
L
V
VCELL
VCELL
VCELL
VCELL
VCS
VCS2–VCS
V
SS
SS
2
(1)
1
) is amplified internally with a gain
–VCS
25
1
2
3
4
–VCELL
–VCELL
–VCELL
–Vss (VCELL
VCS
2
1
(VCS

(VCS
AO OUTPUT
and since the resolution
1
2
3
4
and VCS
(VCELL
(VCELL
(VCELL
12
21
SENSE
)
)
4
(2)
(2)
)
12
23
34
) is small
2
)
)
)
can be
X3102
The internal gain of the X3102 current sense voltage
amplifier can be selected by using the WCNTR Instruction to
set bits CSG1 and CSG0 in the control register (Table 14).
The CSG1 and CSG0 bits select one 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.
VCS
voltage of 2.5V. Therefore, the voltage range of VCS
VCS
(i.e. battery cells are in Charge or Discharge - Table 21).
By calculating the difference of VCS
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
TABLE 26. AO VOLTAGE RANGE FOR VCS
VCS
VCS
VCS
VCS
1
21
AO
and VCS
changes depending upon the direction of current flow
21
21
12
12
VCS
1
=
Shifters
Voltage
R
Level
CELL STATE
R1
FIGURE 15. MONITOR CIRCUIT
--------------------------------------------------------------------------------------------------------- -
2 gain setting
SENSE
2
Discharge
Discharge
are read at AO with respect to a DC bias
Charge
Charge
R2
R1
VCS
2.5V
Register
Cross-Bar
Config
Switch
2
VCS
Cell 1 Voltage
Cell 2 Voltage
Cell 3 Voltage
Cell 4 Voltage
CSG1 CSG0
+
-
(current sense resistor)
12
OP1
–
R2
Setting
Gain
AO VOLTAGE RANGE
VCS
12
2.5V
2.5V
0V
0V
21
Overcurrent
and VCS
Protection
d
d
d
d
AO
AO
AO
AO
12
SPI
I/F
d
d
AND VCS
d
d
December 22, 2004
21
2.5V
2.5V
5.0V
5.0V
the offset
12
X3102
FN8246.0
S0
SCL
CS
SI
AS0
AS1
AS2
AO
and
21
P-