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LTC4155

4155fc

curve 2 thermistor. The critically hot temperature indica-

tion is cleared when NTCVAL rises to decimal result 23.

This corresponds to αCRITICAL,RESET = 0.341 and 55.5°C

for a Vishay curve 2 thermistor.

It is possible to modify the thermistor bias network to

adjust either one or two of the above temperature thresh-

olds. Because of the limited degrees of freedom in the

bias network, the remaining temperature threshold(s) will

then be constrained by the chosen network and thermistor

properties. See Alternate NTC Thermistors and Biasing in

the Applications Information section for implementation

details.

Overtemperature Battery Conditioner

Since Li-Ion batteries deteriorate with full voltage and

high temperature, the LTC4155 contains an automatic

battery conditioner circuit that reduces the battery volt-

age if both high temperature and high voltage are present

simultaneously.

OPERATION

Recall that battery charging is inhibited if the thermistor

temperature reaches 40°C. If the thermistor temperature

climbs above 60°C, and the battery conditioner circuit

is enabled, an internal load of approximately 125mA is

applied to BATSNS. Once the battery voltage drops to

3.9V, or the thermistor reading drops below 55.5°C, the

internal load is disabled. Battery charging resumes once

the thermistor temperature drops below 37°C.

When activated via the I2C port, the battery conditioner

operates whether or not external power is available,

charging has terminated or charging has been disabled

by I2C control. The battery conditioner is controlled by

the EN_BAT_CONDITIONER bit located at I2C sub address

0x00 (Table 6).

Note that this circuit can dissipate significant power inside

the LTC4155. To prevent an excessive temperature rise of

the LTC4155, the LTC4155 reduces discharge current as

needed to prevent a junction temperature rise above 120°C.

LTC4099 Datasheet(PDF) 34 Page - Linear Technology