LTC4095EDC データシートの表示（PDF） - Linear Technology

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LTC4095EDC

Standalone USB Li-Ion/Polymer Battery Charger in 2mm × 2mm DFN

Linear Technology 

LTC4095

OPERATION

NTC Thermistor

The battery temperature is measured by placing a nega-

tive temperature coefficient (NTC) thermistor close to the

battery pack. The NTC circuitry is shown in Figure 3.

To use this feature, connect the NTC thermistor, RNTC,

between the NTC pin and ground, and a bias resistor,

RNOM, from IN to NTC. RNOM should be a 1% resistor with

a value equal to the value of the chosen NTC thermistor

at 25°C (R25). A 100k thermistor is recommended since

thermistor current is not measured by the LTC4095 and

its current will have to be considered for compliance with

USB specifications.

The LTC4095 will pause charging when the resistance of

the NTC thermistor drops to 0.54 times the value of R25

or approximately 54k (for a Vishay “Curve 1” thermistor,

this corresponds to approximately 40°C). If the battery

charger is in constant voltage mode, the safety timer will

pause until the thermistor indicates a return to a valid

temperature.

As the temperature drops, the resistance of the NTC therm-

istor rises. The LTC4095 is also designed to pause charging

when the value of the NTC thermistor increases to 3.25

times the value of R25. For a Vishay “Curve 1” thermistor,

this resistance, 325k, corresponds to approximately 0°C.

The hot and cold comparators each have approximately

3°C of hysteresis to prevent oscillation about the trip point.

Grounding the NTC pin disables all NTC functionality.

POWER

ON

FAULT

NO FAULT, BAT ≤ 2.9V

DUVLO, UVLO AND SUSPEND

IF SUSP < 0.4V AND

IN > 4V AND

IN > BAT + 165mV

FALSE

SUSPEND/SHUTDOWN MODE

CHRG HIGH IMPEDANCE

TRUE

NTC FAULT

BATTERY CHARGING SUSPENDED

CHRG PULSES

NO FAULT

2.9V < BAT < 4.105V

STANDBY MODE

NO CHARGE CURRENT

CHRG HIGH IMPEDANCE

TRICKLE CHARGE MODE

1/10 FULL CHARGE CURRENT

CHRG STRONG PULL-DOWN

30 MINUTE TIMER BEGINS

BAT > 2.9V

CONSTANT CURRENT MODE

FULL CHARGE CURRENT

CHRG STRONG PULL-DOWN

30 MINUTE

TIMEOUT

4 HOUR CHARGE

CYCLE BEGINS

DEFECTIVE BATTERY

NO CHARGE CURRENT

CHRG PULSES

CONSTANT VOLTAGE MODE

4 HOUR TERMINATION

TIMER BEGINS

4 HOUR

TIMEOUT

BAT DROPS BELOW 0.105V

4 HOUR TERMINATION TIMER RESETS

4095 F02

Figure 2. State Diagram of LTC4095 Operation

4095fa

10

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