ISL78610 Datasheet, PDF (43/98 Pages) Intersil Corporation – Multi-Cell Li-Ion Battery Manager

ISL78610
Measure Command
When a device receives the Measure command to its stack
address, it increments the scan counter (see “Scan Counter” on
page 43) and begins a Measure operation.
This command initiates the voltage measurement of a single cell
voltage, internal temperature, any of the four external
temperature inputs, or the secondary voltage reference. The
command incorporates a 6-bit suffix that contains the address of
the required measurement element. See Table 12 on page 43
and Figure 64B on page 55.
The device matching the target address responds by conducting
the single measurement and loading the result to local memory.
The host microcontroller then reads from the target device to
obtain the measurement result. All devices revert to the Standby
state on completion of this activity.
TABLE 12. MEASURE COMMAND TARGET ELEMENT ADDRESSES
MEASURE COMMAND
(SUFFIX)
DESCRIPTION
6’h00
6’h01
V_BAT Voltage
Cell 1 Voltage
6’h02
Cell 2 Voltage
6’h03
6’h04
Cell 3 Voltage
Cell 4 Voltage
6’h05
6’h06
Cell 5 Voltage
Cell 6 Voltage
6’h07
Cell 7 Voltage
6’h08
Cell 8 Voltage
6’h09
Cell 9 Voltage
6’h0A
Cell 10 Voltage
6’h0B
Cell 11 Voltage
6’h0C
6’h10
Cell 12 Voltage
Internal temperature reading
6’h11
6’h12
External temperature input 1 reading.
External temperature input 2 reading.
6’h13
External temperature input 3 reading.
6’h14
External temperature input 4 reading.
6’h15
Reference voltage (raw ADC) value. Use this
value to calculate corrected reference voltage
using reference coefficient data.
Scan Counter
Since the Scan and Measure commands do not have a response,
the scan counter is provided to allow confirmation of receipt of
the Scan and Measure commands. This is a 4-bit counter located
in the Scan Count register (page 1, address 6’h16). The counter
increments each time a Scan or Measure command is received.
This allows the host microcontroller to compare the counter
value before and after the Scan or Measure command was sent
to verify receipt. The counter wraps to zero when overflowed.
The scan counter increments whenever the ISL78610 receives a
Scan or Measure command. The ISL78610 does not perform a
requested Scan or Measure function if there is already a Scan or
Measure function in progress, but it still increments the scan
counter.
Temperature Monitoring Operation
One internal and four external temperature inputs are provided
together with a switched bias voltage output (TEMPREG, pin 29).
The voltage at the TEMPREG output is nominally equal to the
ADC reference voltage such that the external voltage
measurements are ratiometric to the ADC reference (see
Figure 50 on page 29).
The temperature inputs are intended for use with external
resistor networks using NTC type thermistor sense elements but
may also be used as general purpose analog inputs. Each
temperature input is applied to the ADC via a multiplexer. The
ISL78610 converts the voltage at each input and loads the 14-bit
result to the appropriate register.
The TEMPREG output is turned “on” in response to a Scan
Temperatures or Measure Temperature command. A dwell time
of 2.5ms is provided to allow external circuits to settle, after
which the ADC measures each external input in turn. The
TEMPREG output turns “off” after measurements are completed.
Figure 59 on page 44 shows an example temperature scan with
the ISL78610 operating in Scan Continuous mode with a scan
interval of 512ms. The preceding voltage and wire scans are
shown for comparison.
The external temperature inputs are designed such that an open
connection results in the input being pulled up to the full scale
input level. This function is provided by a switched 10MΩ pull-up
from each input to VCC. This feature is part of the fault detection
system and is used to detect open pins.
The internal IC temperature, along with the Auxiliary Reference
Voltage, and multiplexer loopback signals, are sampled in
sequence with the external signals using the Scan Temperatures
command.
The converted value from each temperature input is also
compared to the external over-temperature limit and open
connection threshold values on condition of the [TST4:1] bits in
the Fault Setup register (see “Fault Setup:” on page 85.) If a TSTn
bit is set to “1”, then the temperature value is compared to the
External Temperature threshold and a Fault occurs if the
measured value is lower than the threshold value. If a TSTn bit is
set to “0”, then the temperature measurement is not compared
to the threshold value and no fault occurs. The [TST4:1] bits are
“0” by default.
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June 16, 2016