MAX17843 datasheet(76/131 Pages) MAXIM

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Shutdown Diagnostic

The shutdown diagnostic verifies that no hardware fault

is preventing the device from shutting down, such as

the SHDNL input being stuck at logic-one. To perform

the diagnostic, the host attempts a shutdown. The tim-

ing shown in Figure 48 is for a UART idle mode shut-

down. Once VSHNDL < 0.6V, the ALRTSHDNL bit is set

in the STATUS register and the regulator is disabled

(see Table 41); however, the STATUS register can still

be read as long as VAA has not decayed below 2.95V

(typ), which takes about 1ms. The host should verify that

ALRTSHDNL is set. By reading the bit, the charge pump

will drive VSHDNL > 1.8V in about 200μs and enable

the regulator. The host must clear the ALRTSHDNL bit

to complete the diagnostic. The ALRTSHDNLRT bit is a

real-time version of ALRTSHDNL that automatically clears

when VSHDNL > 1.8V.

HVMUX Switch Open Diagnostic

Since an open HVMUX switch causes the measured

voltage to go to either zero or full-scale, it is possible to

execute the test by looking for an overvoltage or under-

voltage alert following the diagnostic measurement with-

out analyzing the measurement data. It is possible to read

all voltage measurements and let the host compare the

results by splitting the test into several segments.

The procedure in Figure 49 is quick and efficient. For

higher sensitivity to faults, each cell voltage measurement

in the diagnostic mode can be compared to a threshold

of 100mV by the host to determine if the HVMUX path is

working correctly. The threshold is derived from the worst

case HVMUX resistance mismatch and the worst-case

diagnostic current source value variation.

Figure 47. Test Current Sources

Cn-1

RFILTER

RHVMUX

CELL n

LSAMP

TO ADC

VAA

AGND

CELL TEST

CURRENT

SOURCE

CELL TEST

CURRENT

SOURCE

AGND

HVMUX TEST SOURCES

CONTROLLED BY:

MUXDIAGEN

MUXDIAGPAIR

MUXDIAGBUS

CTSTDAC

CELL TEST SOURCES

CONTROLLED BY:

CTSTENn

CTSTSRC

CTSTDAC

RHVMUX

VAA

AGND

RFILTER

MAX17843

12-Channel, High-Voltage Smart Sensor

Data-Acquisition Interface

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