MAX17823H datasheet(39/129 Pages) MAXIM

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Maximum Cell-Balancing Current

The maximum balancing current is limited by package

power dissipation, average die temperature, average duty

cycle of the switch, and the number of switches conduct-

ing current at any one time.

The power dissipation must not exceed the absolute

maximum rating of the package, nor should the die tem-

perature go outside the range specified for the desired

level of measurement accuracy. Higher die temperatures

and higher average duty cycles increase the probability

of internal electromigration, so the maximum balancing

current is lowered accordingly for an assumed 10-year

device lifetime, as shown in Table 11.

Cell-Balancing Watchdog

Even if the host fails to disable the cell-balancing mode, the

cell-balancing watchdog can automatically disable the cell-

balancing switches, regardless of the BALSWEN configu-

ration. The cell-balancing watchdog does not modify the

contents of the BALSWEN register. Use the WATCHDOG

(64min), as shown in Table 12. The pre-divider configura-

tion, CBPDIV[2:0], effectively sets the rate at which the

CBTIMER[3:0] counts down (see Figure 16).

The host should periodically update CBTIMER to ensure

that it does not count down to zero. If the countdown timer

is allowed to reach zero, the cell-balancing switches are

disabled until the timer is either disabled or refreshed by

writing a non-zero value.

To allow timed balancing with no host interaction, the

GPIO3 pin is configured to output a logic-high level while

the timer is counting using the GPIO3TMR configuration

bit of the GPIO register. An external diode is connected

from GPIO3 to SHDNL to prevent shutdown while the

timer is counting. Once the timer expires, the device shuts

down. The host may intervene prior to the timer expiring

to keep the device active and to reconfigure the device.

Table 11. Maximum Allowed Balancing Current per Switch

Table 12. Cell-Balancing Watchdog Configuration

Figure 16. Cell-Balancing Watchdog

CBPDIV

32.768kHz

CBTIMER

TIMER ZERO

FLAG

BIT 0

BIT 1

BIT 2

BIT 3

CBPDIV1 CBPDIV0

BALSWEN

CELL BALANCING

SWITCH ENABLE

CBTIMER ENABLE

CBPDIV2

AVERAGE LIFETIME DUTY CYCLE

(10 YEARS)

TDIE = 85°C

TDIE = 105°C

TDIE = 125°C

15%

650mA

20%

650mA

25%

650mA

CBPDIV[2:0]

TIMER LSB PERIOD

RANGE OF CBTIMER[3:0]

MINIMUM

MAXIMUM

000b

Timer Disabled

001b

15s

010b

60s

011b

16s

240s

100b

64s

960s

101b

128s

1920s

110b

256s

3840s

MAX17823H

12-Channel, High-Voltage

Data-Acquisition Systems

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