ZSC31015 datasheet(21/52 Pages) IDT

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November 14, 2016

ZSC31015 Datasheet

Table 2.3

Summary of Diagnostic Features

Detected Fault

Analog

Diagnostic Level

ZACwire

TM Diagnostic

Delay in Detection

EEPROM signature

Lower

Generates parity error

10ms after power-on

Loss of bridge positive

Upper

Generates parity error

2ms

Loss of bridge negative

Upper

Generates parity error

2ms

Open bridge connection

Upper

Generates parity error

2ms

Bridge input short

Upper

Generates parity error

2ms

ExtTemp pin open

Lower

Generates parity error

300ms

ExtTemp pin shorted to PWR/GND

Lower

Generates parity error

300ms

ExtTemp pin shorted to BP/BN

†

Upper

Generates parity error

3ms

Loss of VDD

Lower

Transmissions stop

Dependent on RL and CL

Loss of VSS

Upper

Transmissions stop

Dependent on RL and CL

2.6.1.

EEPROM Integrity

The contents of the EEPROM are protected by an 8-bit LFSR signature (linear feedback shift register). This sig-

nature is regenerated and stored in EEPROM every time EEPROM contents are changed. This signature is gen-

erated and checked for a match after Power-On-Reset prior to entering Normal Operation Mode. If the generated

signature fails to match, the part will output a diagnostic state on the output.

In addition to an extensive temporal and code interlock mechanism used to prevent false writes to the EEPROM,

the ZSC31015 offers an EEPROM lock mechanism for high-security applications. When EEPROM bits 105:103

are programmed with “011” or “110,” this 3-bit field will permanently disable the VPP charge pump and will not

allow further writes to the EEPROM. See Table 2.3 in section 2.6 for more information.

2.6.2.

Sensor Connection Check

Four dedicated comparators permanently check the range of the bridge inputs (BP/BN) to ensure they are within

the envelope of 0.8V to 0.85

VDD during all conversions. The two sensor inputs have a switched ohmic path to

ground and if left floating, would be discharged. If any of the wires connecting the bridge break, this mechanism

will detect it and put the ZSC31015 in a diagnostic state. This same diagnostic feature can also detect a short

between BP/BN and the ExtTemp signal if an external diode is being used for temperature measurement. See

Table 2.3 in section 2.6 for more information.

†

A short from ExtTemp to BP/BN might not be detected in some circuit configurations.

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