LTC4063 datasheet(14/20 Pages) LINER

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LTC4063

4063fc

applicaTions inForMaTion

Figure5.StateDiagramofaChargerCycleUsingUserTermination

Figure6.TwoCircuitsthatChargeat500mA

Full-ScaleCurrentandTerminateat50mA

CHARGE MODE

FULL CURRENT

4063 F05

TRICKLE CHARGE MODE

1/10 FULL CURRENT

BAT > 2.9V

BAT < 2.9V

2.9V < BAT

CHGEN = 5V

UVLO CONDITION

SHUTDOWN MODE

ICC DROPS TO 35µA

CHRG STATE: Hi-Z

CHRG STATE: PULL-DOWN

POWER ON

CHGEN = 0V

OR UVLO

CONDITION

STOPS

CHRG STATE:

PULL-DOWN IF IBAT > IDETECT

Hi-Z IF IBAT < IDETECT

With User-Selectable Charge Termination, the SmartStart

feature is disabled; when the charger is powered on or

enabled, the LTC4063 automatically begins charging, re-

gardless of the battery voltage. Figure 5 describes charger

operation when User-Selectable Charge Termination is

used.

ProgrammingC/10CurrentDetection/Termination

In most cases, an external resistor, RDET, is needed to set

the charge current detection threshold, IDETECT. However,

when setting IDETECT to be 1/10th of ICHG, the IDET pin

can be connected directly to the PROG pin. This reduces

the component count, as shown in Figure 6.

When PROG and IDET are connected in this way, the

full-scale charge current, ICHG, is programmed using a

different equation:

PROG

CHG

PROG

500

StabilityConsiderations

The battery charger constant voltage mode feedback loop

is stable without any compensation provided a battery

is connected. However, a 1µF capacitor with a 1Ω series

resistor to GND is recommended at the BAT pin to keep

ripple voltage low when the battery is disconnected.

When the charger is in constant current mode, the PROG

pin is in the feedback loop, not the battery. The constant

current stability is affected by the impedance at the PROG

pin. With no additional capacitance on the PROG pin, the

charger is stable with program resistor values as high as

10k; however, additional capacitance on this node reduces

the maximum allowed program resistor.

FortheLDOregulator,acapacitor(COUT)mustbeconnected

from OUT to GND to ensure regulator loop stability. It is

recommended that low ESR capacitors be used for COUT

to reduce noise on the output of the linear regulator. COUT

must be ≥2µF for best performance.

VCC

PROG

IDET

VIN

BAT

500mA

TIMER

RDET

RPROG

LTC4063

GND

VCC

PROG

IDET

VIN

4063 F06

BAT

500mA

TIMER

RPROG

LTC4063

GND

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