MAX11068EVKIT+ Maxim Integrated Products, MAX11068EVKIT+ Datasheet - Page 21

• 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: -

Figure 11. Measurement Scan Timing for a Multimodule System
For every module in the battery pack, a 1Fs communi-
cation delay is incurred while the scan command is for-
warded up the SMBus ladder. Therefore, the difference
in the scan completion time from the first module to the
last module in a chain is no more than 1Fs x (no. of mod-
ules in the chain - 1) as shown in Figure 11.
Taking the module conversion time and combining it with
the communication delay, the overall sampling window
of the system can be calculated:
So, for a battery pack that uses 12 cells per module and
a system with four modules (total cell count = 48), the
sampling window would be:
enabled per module -1) x 3.83Fs) x 2 phases + ((no. of
Sampling Window = 11.3 + (5.67 + 11 x 3.83Fs) x 2 +
Sampling window = 11.3Fs + (5.67Fs + (no. of cells
Sampling Window = (106.9Fs) + (3Fs) = 109.9Fs
modules per pack - 1) x 1Fs per module)
COMMAND FORWARDING
12-Channel, High-Voltage Sensor, Smart
((4 Modules -1) x 1Fs)
DELAY = 1µs
SCAN AT t
MODULE 1
0
MODULE 2
t
ALL MODULES
MODULE 3
Data-Acquisition Interface
MODULE 4
MODULE 5
= (NO. OF MODULES X 1µs) + 107µs
Thus, from the time the first device receives the scan
command until the last device completes its measure-
ment conversion, 109.9Fs elapse.
The final aspect of the measurement conversion is the
retrieval of data from all devices. A READALL command
is the only way to transfer data from each device. Since
up to 12 cells are measured, the READALL command
must be performed for each cell whose data must be
transferred. For each READALL command, there are 5
total bytes of overhead. These include the broadcast
address byte, the command code byte (register address
to be read), the I
and the packet-error check (PEC) byte. Each of these
bytes has an acknowledge bit associated with it. The
register data from each device consists of 2 more bytes
plus 2 acknowledge bits. Finally, the overall data stream
consists of 3 more bits, start, stop, and repeated start.
Thus, for a read of a single register from all modules, the
total bit count is:
READALL bit count = 3 + 5 x 8 + 5 + no. of modules x
MODULE N
2
C address byte, the data check byte,
(2 x 8 + 2) = 120
t
ALL MODULES
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