MAX17843ACB datasheet(69/131 Pages) MAXIM

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Full-Scale ADC Diagnostic Measurement

Stuck ADC output bits can be verified with a combination

of the zero-scale and full-scale diagnostics. The zero-

scale ADC diagnostic measurement (DIAGSEL[2:0] =

0b101) verifies that the ADC conversion results in FFFh

when its input is at VAA in bipolar mode (since for an input

≥ 2.5V, DIAG[15:0] = FFF0h). For this measurement, the

ADC is automatically set to bipolar mode.

BALSW Diagnostics

Four balancing switch diagnostic modes are available to

facilitate the following diagnostics:

● Balancing switch shorted (BALSWDIAG[2:0] = 0b001)

● Balancing switch open (BALSWDIAG[2:0] = 0b010)

● Odd sense wire open (BALSWDIAG[2:0] = 0b101)

● Even sense wire open (BALSWDIAG[2:0] = 0b110)

Enabling any of these modes automatically preconfigures

the acquisition (e.g. enables the ALTMUX measurement

path). The host must initiate the acquisition but the diag-

nostic mode automatically compares the measurements

to the specific thresholds, and sets any corresponding

alerts. The host presets the thresholds as determined

by the minimum and maximum resistance of the switch

(RSW) specified in the Electrical Characteristics table and

the intended cell-balancing current.

During any balancing switch diagnostic mode, ALRTOV,

ALRTUV and ALRTMSMTCH comparisons are dis-

abled. After BALSWDIAG[2:0] is cleared, the modified

configurations automatically return to their prior setting. The

same configurations and comparisons could be implement-

ed manually but at the expense of more host operations.

BALSW Short Diagnostic

A short-circuit fault in the balancing path could be a short

between SWn and SWn-1 (see Figure 42), or that the

balancing FET is stuck in the conducting state. In the

short circuit state, the voltage between SWn and SWn-1

(switch voltage) is less than the voltage between Cn and

Cn-1 (cell voltage).

When enabled, the balancing switch short diagnostic

mode (BALSWDIAG[2:0] = 0b001) functions as follows:

● Disables the balancing switches automatically

● Configures the acquisition using ALTMUX path auto-

matically

● Host initiates the acquisition

● Compares the measurement to the threshold value

BALSHRTTHR automatically

● If outside the threshold, sets the corresponding flag in

ALRTBALSW automatically

For the best sensitivity to leakage current, set the threshold

value based on the minimum cell voltage minus a small

noise margin (100mV), then update the threshold value

periodically or every time a measurement is taken, depend-

ing on how fast the cell voltages are expected to change.

Figure 41. ADC Full-Scale Diagnostic

ADC IN -

ADC IN +

MUX

ADC

REF

THRM

AGND

VAA

AGND

ADC AUTOMATICALLY

IN BIPOLAR MODE

MAX17843

12-Channel, High-Voltage Smart Sensor

Data-Acquisition Interface

www.maximintegrated.com

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