ISL78610 Datasheet, PDF (24/98 Pages) Intersil Corporation – Multi-Cell Li-Ion Battery Manager

ISL78610
CELL BALANCE CONNECTION
The ISL78610 uses external MOSFETs for the cell balancing
function. The gate drive for these is derived from on-chip current
sources on the ISL78610 which are 25µA nominally. The current
sources are turned on and off as needed to control the external
MOSFET devices. The current sources are turned off when the device
is in Shutdown mode or Sleep mode. The ISL78610 uses a mix of
N-channel and P-channel MOSFETs for the external balancing
function. The top three cell locations, cells 10, 11, 12 are configured
to use P-channel MOSFETs while the remaining cell locations, cells 1
through 9, use N-channel MOSFETs. The mix of N-channel and
P-channel devices are used for the external FETs in order to remove
the need for a charge pump, while providing a balance FET gate
voltage that is sufficient to drive the FET on, regardless of the cell
voltages.
Figures 41 and 43 shows the circuit detail for the recommended
balancing and cell voltage monitoring system. In this
configuration, the cell voltage is monitored after the cell balance
resistor. This allows the system to monitor the operation of the
external balance circuits and is part of the fault detection
system. However, this connection prevents monitoring the cell
voltage while cell balance is enabled for that cell.
Figure 41 shows the connection for VC12. This connection uses
P-channel FETs and is similar for VC11 and VC10. Similarly,
Figure 43 shows the connection for VC1, using an N-channel FET,
with the connections for VC2 through VC9 being similar. See
Figure 51 on page 31 for a more complete example.
An alternative balancing and cell voltage monitoring
arrangement is shown in Figure 42 and Figure 44. The diagram
in Figure 42 shows the connection for VC10 through VC12, using
P-channel FETs. Figure 44 shows the connection for VC1 through
VC9. using N-channel FETs. With this alternative circuit it is
possible to monitor the cell voltages during cell balancing (even
though the voltage will likely drop a little when measuring a cell
that is being balanced). But this circuit connection does not allow
the system to check for all potential external component failures.
See Figure 54 on page 34 for a more complete example.
ISL78610
FIGURE 41. CELL MONITOR AND BALANCE CIRCUIT
ARRANGEMENT (VC12)
ISL78610
FIGURE 42. ALTERNATE CELL MONITOR AND BALANCE CIRCUIT
ARRANGEMENT (VC10 TO VC12)
ISL78610
FIGURE 43. CELL MONITOR AND BALANCE CIRCUIT
ARRANGEMENT (VC1)
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ISL78610
FIGURE 44. ALTERNATE CELL MONITOR AND BALANCE CIRCUIT
ARRANGEMENT (VC1 TO VC9)
FN8830.1
June 16, 2016