14

LTC4063

4063fb

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.

Programming C/10 Current Detection/Termination

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-

ent equation:

R

V

I

I

V

R

PROG

CHG

CHG

PROG

==

500

500

,

Stability Considerations

The battery charger constant voltage mode feedback loop

is stable without any compensation provided a battery is

connected. However, a 1

µF 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.

nected from OUT to GND to ensure regulator loop stability.

It is recommended that low ESR capacitors be used for

APPLICATIO S I FOR ATIO

CHARGE MODE

FULL CURRENT

4063 F05

TRICKLE CHARGE MODE

1/10 FULL CURRENT

BAT > 2.9V

BAT < 2.9V

2.9V < BAT

CHGEN = 5V

OR

UVLO CONDITION

SHUTDOWN MODE

CHRG STATE: Hi-Z

CHRG STATE: PULL-DOWN

POWER ON

CHGEN = 0V

OR UVLO

CONDITION

STOPS

CHRG STATE:

Figure 5. State Diagram of a Charger Cycle Using User Termination

+

PROG

IDET

BAT

500mA

TIMER

2k

2k

LTC4063

GND

+

PROG

IDET

4063 F06

BAT

500mA

TIMER

1k

LTC4063

GND

Figure 6. Two Circuits that Charge at 500mA

Full-Scale Current and Terminate at 50mA