tion for this test-mode compare level. If all comparators

can detect the internally generated overvoltage test

event, part operation continues. If any comparator fails

to detect the internally generated overvoltage test

device must be power cycled to retest the comparators

and attempt to clear this fault condition.

Failure Mode and Effects Analysis

High-voltage battery-pack systems can be subjected to

severe stresses during in-service fault conditions and

could experience similar conditions during the manu-

facturing and assembly process. The MAX11080 is

designed with high regard to these potential states.

Open and short circuits at the package level must be

readily detected for fault diagnosis and should be toler-

ated whenever possible. A number of circuits are

employed within the MAX11080 specifically to detect

such conditions and progress to a known device state.

Table 3 summarizes other conditions typical in a normal

manufacturing process along with their effect on the

MAX11080 device.

See Table 4 for the FEMA analysis of the MAX11080. If

the cell voltage is within the monitor range, the heart-

beatsignal on the ALRML resumes once the fault condi-

tion (either open or short) is removed, unless specified.

12-Channel, High-Voltage Battery-Pack

Fault Monitor

______________________________________________________________________________________

21

CONDITION

EFFECT

DESIGN RECOMMENDATION

PCB or IC package open or short circuit—

no stack load

Refer to the pin-level FMEA analysis

spreadsheet available from the factory

The built-in features of the MAX11080

should ensure low FMEA risk in most

cases.

Random connection of cells to IC—

no stack load

No effect

The series resistors on the cell inputs of

the MAX11080 as well as the internal

design ensure protection against random

power supply or ground connections.

Random connection of modules—

no stack load

No effect

Each module is referenced to its neighbor,

so no special connection order is

necessary.

Random connect/disconnect of

communication bus—no stack load;

AC- or DC-coupled

Communication from host to the first break

in the daisy-chain bus

The level-shifted interface design of the

MAX11080 ensures that the

and ALRM_ communication bus can be

connected at any time with no load.

Random connect/disconnect of

communication bus—with stack load;

AC- or DC-coupled

Communication from host to the first break

in the daisy-chain bus

The level-shifted interface design of the

MAX11080 ensures that the

ALRM_ communication bus can be

connected at any time as long as the

power bus is properly connected.

Connect/disconnect module interconnect

(bus bar)—no stack load

No effect for DC- or AC-coupled

communication bus

A break in the power bus does not cause

a problem as long as there is no load on

the stack.

Removal/fault of module interconnect

(bus bar)—with stack load

No effect for AC-coupled communication

bus; device damage for DC-coupled bus

An AC-coupled bus with isolation on the

SHDN pin or a redundant bus-bar

connection should be used to protect

against this case.

Removal/fault of module interconnect

(bus bar)—with stack under charge

No effect for AC-coupled communication

bus; device damage for DC-coupled bus

An AC-coupled bus with isolation on the

SHDN pin or a redundant bus-bar

connection should be used to protect

against this case.

Table 3. System Fault Modes