12-Channel, High-Voltage Battery-Pack

Fault Monitor

14

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(+2.4V minimum as referred to AGND), it transitions

back to a heartbeat signal only after all battery cells

meet the following condition:

Examples of cell-voltage readings and their effect on

the alarm status are shown in Figures 9 and 10 for sin-

gle- and multiple-cell systems. In the case where an

upper module is forwarding an active alarm condition

down the daisy chain, that condition continues to be

propagated toward the host regardless of the alarm

state of any lower module. Furthermore, to circumvent

the possibility of a short-circuited capacitor connected

to CD preempting the fault-time validation process, a

redundant built-in delay of 4s nominal is asserted as a

an out-of-range event, the alarm becomes active.

Programmable Delay Time

The alarm trigger delay time is calculated according to

the following equations:

The VCD threshold is specified at an internal node prior

to the resistor in series with the CD pin as shown in

Figure 8. The threshold voltage seen at the pin is

approximately 1.18V due to the drop associated with

the typical ICD value and the 6k

Ω resistor. The

MAX11080 can operate with capacitor values from

15nF (3.0ms) to 16.5µF (3.32s). Each capacitor should

have a voltage tolerance of 5V minimum.

Cell-Voltage Threshold Selection

The overvoltage and undervoltage threshold selection

is configured through the OVSEL_ and UVSEL_ inputs.

The overvoltage selection can be configured from 3.3V

to 4.8V in 100mV increments. The undervoltage thresh-

old can be configured from 1.6V to 2.8V in 200mV

increments. The undervoltage detection can also be

disabled. See Tables 1 and 2 for the proper configura-

tion settings.

Immunity to unintended changes in the threshold volt-

age setting (due to accidental pin-to-pin short circuits,

for example) is provided. The customer-programmed

selection is sensed and stored at power-up and any

subsequent change to the input pin status is ignored.

OVERVOLTAGE SELECTION

THRESHOLD (V)

OVSEL3

OVSEL2

OVSEL1

OVSEL0

3.3

0

0

0

0

3.4

0

0

0

1

3.5

0

0

1

0

3.6

0

0

1

1

3.7

0

1

0

0

3.8

0

1

0

1

3.9

0

1

1

0

4.0

0

1

1

1

4.1

1

0

0

0

4.2

1

0

0

1

4.3

1

0

1

0

4.4

1

0

1

1

4.5

1

1

0

0

4.6

1

1

0

1

4.7

1

1

1

0

4.8

1

1

1

1

Table 1. Overvoltage Threshold Selection