MAX11068EVKIT+ Maxim Integrated Products, MAX11068EVKIT+ Datasheet - Page 20

• Manufacturer Part Number: MAX11068EVKIT+
• Description: KIT SMART BATT MEASUREMENT 12CH
• Manufacturer: Maxim Integrated Products

Specifications of MAX11068EVKIT+

• Main Purpose: Power Management, Battery Monitor, Car
• Utilized Ic / Part: MAX11068
• Primary Attributes: Monitors Current, Voltage, Temperature
• Secondary Attributes: 1 ~ 12 Cell- Li-Ion, 1 ~ 12 Cell- NiMH
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Embedded: -

12-Channel, High-Voltage Sensor, Smart
Data-Acquisition Interface
Figure 10. Cell-Scanning Timing
The second stage in the channel-scanning process
is the correction phase, where the front-end amplifier
chops out any offset and reference-induced errors. This
provides a high-accuracy cell voltage result. In this
stage, the channels are converted in the same highest
to lowest order as the initial measurement. The module-
to-module sampling points differ by the communication
forwarding delay from the I
surements from the two scan phases complete, the ADC
data is then offset corrected, averaged, and updated in
the cell data registers.
After the cell-measurement cycle is complete, the self-
diagnostic channel is acquired when enabled. It is a
two-phase measurement as described for the cell-volt-
age inputs, with each phase measured one immediately
after the other. Finally, the enabled auxiliary inputs are
measured. They are measured in a single conversion,
with results reported in the AIN1 and AIN2 registers.
The auxiliary channels have a configurable option to
increase settling time that is set in the lower byte of the
ACQCFG register (address 0x0C). The configured extra
settling time is implemented just before the conversion
for each AUXIN channel that is enabled for measure-
20
t
0
- STROBE POINT
B12+
B11+
B10+
2
t
0
C command. With the mea-
+ 16.97µs
B9+
B8+
B7+
B6+
B5+
B4+
B3+
B2+
B1+
TIME
B12-
ment. So, when both auxiliary channels are measured,
the extra settling time occurs twice. Extra settling time
is not needed by the MAX11068 ADC; it is only for the
benefit of the external application circuit.
The first requirement for performing a measurement
conversion is setting the SCAN bit. This can be done
by using the WRITEALL or WRITEDEVICE commands.
The write commands require 5 full bytes of data, plus 5
acknowledge bits and the start and stop bits. This totals
47 bits of data sent by the host, which would require
235Fs at a 200kHz I
The timing of the cell measurements is shown in Figure
10. At the start of the measurement cycle, there is a
measurement setup time prior to the measurement of the
highest cell totaling 11.3Fs. The highest cell measured
requires a sampling time of 5.67Fs, while the rest of the
inputs are sampled at 3.83Fs per channel. When all 12
channels are enabled, the 12-cell voltages for one phase
are acquired in 47.8Fs, not including the measurement
setup time. The total acquisition time for 12 cells is
106.9Fs
t
0
+ 59.1µs
B11-
B10-
B9-
B8-
Calculating Measurement Time
B7-
B6-
2
C clock rate.
B5-
B4-
OTHER CELLS SAMPLING TIME = 3.83µs
B3-
TOP CELL SAMPLING TIME = 5.67µs
B2-
B1-
t
0
+ 106.9µs