LN2053

Rev.1.1 —Aug. 20, 2015

8

www.natlinear.com

■ Application Information



Kelvin battery voltage detection

When FB and BAT shorted, the output is 3.65V. When FB and BAT opened, the output is 4.2V. If connect a resistor

between the FB pin and BAT pin, the output can be regulated from 3.65V to 4.2V.



Adjust the constant charging voltage

If connect a resistor between the LN2053 battery voltage Kelvin test input pin (FB) and the positive battery , it can increase

the battery charging voltage, as shown in Figure 3, then the positive battery voltage Vbat is:

Vbat (V) ＝

X

X

1.2

142.5

*

* R

3.65

305 142.5

R





When using an external resistor to adjust the charging voltage constant, due to internal and external temperature of chip

and chip production inconsistent with the process variation and other factors, may cause the accuracy of the output voltage

variation and temperature coefficient.



Application of USB and AC adapter while charging at the same time

LN2053 can not only use USB interface to charge the battery, users can also use a wall adapter to charge the battery.

Figure 3 shows the same time using the USB interface and the AC adapter to charge the battery through the LN2053 .when the

two co-exist, the AC adapter has priority. M1 is the P-channel MOSFET, M1 is used to prevent current from a wall adapter into

the USB interface, USB interface, Schottky diode D1 prevents the consumption of energy through the 1K resistor.

Figure3. While using the AC adapter and USB interfaces



Set the charge current

In constant-current mode, formula for calculating charge current: ICH = 1250V / RISET

ICH represents the charge current, units is ampere, RISET represents ISET pin to ground resistance in ohms. For example, if

you need 500mA charge current, according to the following formula: RISET = 1250V/0.5A = 2.5kΩ

In order to ensure good stability and temperature characteristics, RISET recommend the use of 1% precision metal film

resistors. By measuring the ISET pin voltage can be detected charge current. Charge current can be calculated using the

following formula: ICH = (VISET / RISET) × 1250



Battery temperature monitoring

In order to prevent the battery temperature is too high or too low on the battery damage, LN2053 internal battery

temperature monitoring of integrated circuits. Battery temperature monitoring is by measuring the TEMP pin voltage to achieve,