MAX17843 datasheet(27/131 Pages) MAXIM

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Data Conventions

Representation of data follows the conventions shown in

Table 2. All registers are 16-bit words.

Data Acquisition

Data acquisition is composed of the distinct processes

defined in Table 3, and is controlled by various configu-

ration registers described in this section. Configuration

changes should be made prior to the acquisition in which

the changes are to be effected.

Precision Internal Voltage References

The measurement system uses two precision, temper-

ature-compensated voltage references. The references

are completely internal to the device and do not require

any external components. The primary voltage reference

(REF) is used to derive the linear regulator output voltage

and to supply the ADC reference. An alternate, indepen-

dent reference(ALTREF) can be used to verify the primary

reference voltage, as described in the Diagnostics section.

Measurement Calibration

The acquisition system is calibrated at the factory and

cannot be changed afterwards. The calibration param-

eters are stored in a ROM consisting of 12 read-only

registers, CAL0–CAL10 and CAL15. ROMCRC[8:0] is

an 8-bit CRC value based on the calibration ROM and is

stored in ID2[15:8] at the factory. ROMCRC[8:0] can be

used to check the integrity of the calibration, as described

in the Diagnostics section.

Cell Inputs

Up to 12 voltage measurements can be sampled

differentially from the 13 cell inputs. The differential signal

(VCELLn) is defined as VCn - VCn-1 for n = 1–12.

Cells to be measured are selected by MEASUREEN[11:0].

During the scan, each selected signal is multiplexed into

the level-shifting amplifier (LSAMP) as shown in Figure 6.

Since the common-mode range of the input signals is 0 to

65V, the signal must be level-shifted to the common-mode

range of the amplifier. The amplifier has a gain of 6/13, so

a 5V differential signal is attenuated to 2.307V, which is

the ADC reference voltage.

Table 2. Numeric Conventions

Table 3. Data-Acquisition Processes

DESCRIPTION

CONVENTION

EXAMPLE

Binary number

0b prefix

0b01100001 = 61h

Hexadecimal address

0x prefix

0x61

Hexadecimal data

h suffix

61h

STATUS[15] = 1

Field name [x:y]

DA[4:0] = 0b01100 = 0Ch

Concatenated numbers

{xxxx, yyyy}

{DA[4:0], 0b001} = 61h

PROCESS

DESCRIPTION

Conversion

The ADC samples a single input channel, converts it to a 12-bit binary value, and stores it in an

ALU register.

Scan

The ADC sequentially performs conversions on all enabled cell input channels.

Measurement cycle or Sample

The ADC performs two scans for the purpose of minimizing errors. The conversions (two

for each input channel) are averaged together to form a single 14-bit binary value called

a measurement.

Note: The auxiliary inputs are only scanned once to create the auxiliary

measurements.

Acquisition or Acquisition mode

If oversampling is enabled, the ADC takes sequential measurements and averages them

together to form one 14-bit binary value for each input channel sampled. If there is no

oversampling, the acquisition is essentially a single-measurement cycle.

Note: The auxiliary

inputs are never oversampled and are stored as 12-bit values.

MAX17843

12-Channel, High-Voltage Smart Sensor

Data-Acquisition Interface

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