MCP73871 datasheet(17/38 Pages) MICROCHIP

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DS22090B-page 17

MCP73871

3.14

Timer Enable (TE)

The timer enable (TE) feature is used to enable or

disable the internal timer. A low signal on this pin

enables the internal timer and a high signal disables

the internal timer. The TE input can be used to disable

the timer when the system load is substantially limiting

the available supply current to charge the battery. The

TE input is compatible with 1.8V logic.

3.15

Battery Temperature Monitor

(THERM)

The MCP73871 device continuously monitor battery

temperature during a charge cycle by measuring the

voltage between the THERM and VSS pins. An internal

50 µA current source provides the bias for most

common

10 k

Ω negative-temperature coefficient

thermistors (NTC). The MCP73871 device compares

the voltage at the THERM pin to factory set thresholds

of 1.24V and 0.25V, typically. Once a voltage outside

the thresholds is detected during a charge cycle, the

MCP73871 device immediately suspends the charge

cycle. The charge cycle resumes when the voltage at

the THERM pin returns to the normal range. The

charge temperature window can be set by placing fixed

value resistors in series-parallel with a thermistor.

Refer to

Section 6.0 “Applications” for calculations

of resistance values.

3.16

Charge Enable (CE)

With the CE input Low, the Li-Ion battery charger

feature of the MCP73871 will be disabled. The charger

feature is enabled when CE is active High. Allowing the

CE pin to float during the charge cycle may cause

system instability. The CE input is compatible with 1.8V

logic. Refer to

Section 6.0 “Applications” for various

applications in designing with CE features.

3.17

Exposed Thermal Pad (EP)

There is an internal electrical connection between the

Exposed Thermal Pad (EP) and the VSS pin; they must

be connected to the same potential.

Note:

The built-in safety timer is available for the

following options: 4 HR, 6 HR and 8 HR.

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