ISL78610 Datasheet, PDF (23/98 Pages) Intersil Corporation – Multi-Cell Li-Ion Battery Manager

ISL78610
B14b
LOCATE CLOSE
TO INPUT CONNECTOR
27
*EXAMPLE DIODE:
PTVS58VS1UTR
C₁
58V*
VSS
820
180
B12
22nF
ISL78610
VBAT
VC12
820
180
B11
VC11
22nF
820
180
B10
VC10
22nF
820
180
B9
VC9
22nF
820
B3
22nF
820
B2
22nF
820
B1
22nF
820
B0
22nF
B0b
= “QUIET” GROUND
= “NOISY” GROUND
180
VC3
180
VC2
180
VC1
180
VC0
VSS
CELL BALANCE CIRCUITS NOT SHOWN IN THIS FIGURE
FIGURE 38. TYPICAL INPUT FILTER CIRCUITS
The filtered battery voltage connects to the internal cell voltage
monitoring system. The monitoring system comprises three basic
elements; a level shifter to eliminate the cell common-mode
voltage, a multiplexer to select a specific input and an
analog-to-digital conversion of the cell voltage.
Each ISL78610 is calibrated at a specific cell input voltage value,
V_NOM with an expected input series resistance of 1kΩ. Cell voltage
measurement error data is given in “MEASUREMENT
SPECIFICATIONS” on page 8 for various voltage and temperature
ranges with voltage ranges defined with respect to V_NOM. Plots
showing the typical error distribution over the full input range are
included in the “Performance Curves” section beginning on
page 16.
Another important consideration is the connection of cells in a
stacked (non-overlapping) configuration. Mainly, this involves
how to connect the supply and ground pins at the junction of two
devices. The diagram in Figure 39 shows the recommended
minimum connection to the pack. It is preferred that there be
four connection wires at the intersection of two devices, but this
does pose a cost constraint. To minimize the connections, the
power and monitor pins are connected separately, as shown in
Figure 39. It is not recommended that all four wires connect
together with a single wire to the pack. There are two reasons for
this. First, the power supply current for the devices might affect
the accuracy of the cell voltage readings. Second, if the single
wire breaks, it is very difficult for the system to tell specifically
what happened through normal diagnostic methods.
An alternative circuit in Figure 40 shows the connection of one
(or two) wires with additional Schottky diodes to provide supply
current paths to allow the device to detect that there is a
connection fault and to minimize the effects on cell voltage
measurements when there is an open connection to the battery.
820
100
22nF
820 ^VSS2 100
22nF
820 ^VSS2 100
22nF
27
C₁
VSS
820
VSS
100
22nF
820 ^VSS 100
22nF
ISL78610
VC2
VC1
VC0
VSS2
ISL78610
VBAT
VC12
VC11
VSS
FIGURE 39. BATTERY CONNECTION BETWEEN STACKED DEVICES
(OPTION 1)
820
180
22nF
820 ^VSS2 180
22nF
820 ^{VSS2 180}
22nF
27
C₁
VSS
820
VSS
180
22nF
820 ^VSS 180
22nF
VSS
ISL78610
VC2
VC1
VC0
VSS2
ISISLL778671140
VBAT
VC12
VC11
FIGURE 40. BATTERY CONNECTION BETWEEN STACKED DEVICES
(OPTION 2)
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FN8830.1
June 16, 2016