Preliminary Datasheet

LP28055

LP28055 – 02

Oct.-2018

www.lowpowersemi.com

Page 5 of 7

Application Information

Input Voltage Range

The LP28055 has built-in input voltage surge protection as

high as +28V. The charger IC will be automatically disabled

when the input voltage is lower than 3.3V or higher than 7.0V.

A charge cycle begins when the voltage at the VIN pin rises

above the UVLO threshold level,when a battery is connected

to the charger output. If the BAT pin is less than 2.6V, the

charger enters trickle charge mode. In this mode, the P28055

supplies approximately 1/10 the ISET rammed charge current

to bring the battery voltage up to a safe level for full current

charging. When the BAT pin voltage rises above 2.6V, the

charger enters constant-current mode(CC), where the ISET

rammed charge current is supplied to the battery. When the

BAT pin approaches the final float voltage, the LP28055

enters constant-voltage mode(CV) and the charge current

begins to decrease, and the battery full indication is set

whenthe charge current in the CV mode is reduced to the

programmed full battery current (1/10).

Charge Termination

A charge cycle is terminated when the charge current falls to

1/10th the ISET rammed value after the final float voltage is

reached. This condition is detected by using an internal,

filtered comparator to monitor the ISET pin. When the ISET

pin voltage falls below 100mV for longer than tTERM (typically

1ms), charging is terminated.

The LP28055 constantly monitors the BAT pin voltage in

standby mode. If this voltage drops below the 4.05V recharge

is once again supplied to the battery. To manually restart a

charge cycle when in standby mode, the input voltage must

be removed and reapplied, or the charger must be shut down

and restarted using the ISET pin.

ISET ramming Charge Current

connecting from the ISET pin to GND.The relationship of the

charge current and the programming resistance is established

by the following table.

Battery Temperature Detection

The NTC function for the LP28055 is designed to follow the

new JEITA temperature standard for Li-Ion. There are now

three thresholds, 60°C, 10°C, and 0°C. Normal operation

occurs between 10°C and 60°C. If between 0°C and 10°C the

charge current level is cut in half . Above 60°C or below 0°C

the charge is disabled.

The NTC feature is implemented using an internal 48μA

current source to bias the thermistor connected from the NTC

terminal to VSS(designed for use with a 10k NTC β = 3370

(SEMITEC 103AT-2 or Mitsubishi TH05-3H103F)). If this

feature is not needed, a fixed 10kΩ can be placed between

NTC and GND to allow normal operation. Since the INTC

curent is fixed along with the temperature thresholds, it is not

possible to use thermistor values other than the 10k NTC (at

25°C).

Automatic Recharge

Once the charge cycle is terminated, the LP28055

continuously monitors the voltage on the BAT pin .A charge

cycle restarts when the battery voltage falls below 4.05V

(which corresponds to approximately 80% to 90% battery

capacity). This ensures that the battery is kept at or near a

fully charged condition and,eliminates the need for periodic

charge cycle initiations