MAX17823BGCV datasheet(18/121 Pages) MAXIM

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MAX17823B

12-Channel High-Voltage Data Acquisition System

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Maxim Integrated | 18

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 to 12.

The 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 3. Since the common-mode range of the input signals

is 0V 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 that a 5V differential signal will be attenuated to 2.307V which is the ADC reference voltage.

Once the signal is properly conditioned the ADC can start the conversion. The 12-bit conversion is stored in an ALU

stored in a 16-bit register with the two least-significant bits zero. Disabled channels result in a measurement value

of 0000h. Unless stated otherwise, measurement values are assumed to be 14-bit values. The 16-bit register values

can be converted to 14-bit values by dividing by 4 (and vice-versa). To convert the measurement value in register

CELLn to a voltage, convert the 14-bit hexadecimal value to a decimal value and then convert to voltage as follows:

VCELLn = CELLn[15:2] x 5V / 16384 = CELLn[15:2] x 305.176µV.

Input Range

The input range in unipolar mode is nominally 0V to 5V. However, the ADC has reduced linearity at its range extents

and so accuracy is specified for the input range 0.2V to 4.8V. Some applications may require specified accuracy

below 0.2V or even below 0V. To this end, the bipolar mode (POLARITY = 1) has a nominal input range of -2.5V to

2.5V as shown in Table 4 with accuracy specified from -2.3V to 2.3V.

Table 4. Input Range

Cell Input Voltage

CELLn[15:2] (14 Bits)

CELLn[15:0]

(16 Bits)

Bipolar Mode

Unipolar Mode

Hexadecimal

Decimal

-2.5V

0000h

2.5V

2000h

8192d

8000h

2.5V

3FFFh

16383d

FFFCh

The input range can effectively be extended from -2.5V to 5V by taking one bipolar measurement and one unipolar

measurement. Any bipolar measurements over 2.3V should be replaced with the unipolar measurement.

Note: Conversions for some diagnostic modes automatically use either bipolar or unipolar mode regardless of the

POLARITY bit value.

MAX17823BGCV Datasheet(PDF) 18 Page - Maxim Integrated Products

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