LTC4069(RevB) Просмотр технического описания (PDF) - Linear Technology

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производитель

LTC4069
(Rev.:RevB)

Standalone 750mA Li-Ion Battery Charger in 2 × 2 DFN with NTC Thermistor Input

Linear Technology 

LTC4069

OPERATION

POWER

ON

UVLO

NO

IF VCC > 3.6V AND

VCC > VBAT + 80mV?

TEMPERATURE

NOT OK

YES

NTC FAULT

BATTERY CHARGING SUSPENDED

CHRG PULSES (2Hz)

TEMPERATURE NOT OK

VBAT ≤ 2.9V

TEMPERATURE OK

2.9V < VBAT < 4.1V

TRICKLE CHARGE MODE

1/10 FULL CHARGE CURRENT

CHRG STRONG PULL-DOWN

FAST CHARGE MODE

FULL CHARGE CURRENT

CHRG STRONG PULL-DOWN

1/4 CHARGE CYCLE

NO CHARGE CYCLE

NO

(1.125 HOURS)

(4.5 HOURS)

DEFECTIVE BATTERY

IS VBAT < 2.9V?

RECHARGE

IS VBAT < 4.1V?

UVLO MODE

CHRG HIGH IMPEDANCE

VBAT > 4.1V

STANDBY MODE

NO CHARGE CURRENT

CHRG HIGH IMPEDANCE

YES

YES

BAD BATTERY MODE

NO CHARGE CURRENT

CHRG PULSES (2Hz)

VCC < 3V

RECHARGE MODE

FULL CHARGE CURRENT

CHRG STRONG PULL-DOWN

1/2 CHARGE CYCLE

(2.25 HOURS)

4069 F02

Figure 2. State Diagram of LTC4069 Operation

Regardless of mode, the voltage at the PROG pin is

proportional to the current delivered to the battery.

Battery Temperature Monitoring via NTC

The battery temperature is measured by placing a negative

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 resistor, RNOM, from

the NTC pin to VCC. RNOM should be a 1% resistor with a

value equal to the value of the chosen NTC thermistor at

25°C (this value is 100k for a Vishay NTHS0603N01N1003J

thermistor). The LTC4069 goes into hold mode when the

value of the NTC thermistor drops to 0.53 times the value

of RNOM, which corresponds to approximately 40°C,

10

and when the value of the NTC thermistor increases to

3.26 times the value of RNOM, which corresponds to

approximately 0°C. Hold mode freezes the timer and stops

the charge cycle until the thermistor indicates a return to

a valid temperature. For a Vishay NTHS0603N01N1003J

thermistor, this value is 32.6k which corresponds to

approximately 0°C. The hot and cold comparators each

have approximately 3°C of hysteresis to prevent oscillation

about the trip point.

When the charger is in Hold mode (battery temperature is

either too hot or too cold) the CHRG pin pulses in a 2Hz,

25% duty cycle frequency unless the charge task is finished

or the battery is assumed to be defective. If the NTC pin

is grounded, the NTC function will be disabled

4069fb

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