LP4056-02

Aug.-2017

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 6 of 7

Preliminary Datasheet

LP4056

Thermal Limit

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise above a

preset value of approximately 125℃. This feature protects the

LP4056 from excessive temperature and allows the user to

push the limits of the power handling capability of a given

circuit board without risk of damaging the LP4056. The charge

current can be set according to typical (not worst-case)

ambient temperature with the assurance that the charger will

automatically reduce the current in worst-case conditions.

Under voltage Lockout (UVLO)

An internal under voltage lockout circuit monitors the input

voltage and keeps the charger in shutdown mode until VIN

rises above the under voltage lockout threshold .The UVLO

circuit has a built-in hysteresis of 200mV. Furthermore, to

protect against reverse current in the power MOSFET, the

UVLO circuit keeps the charger in shutdown mode if VIN falls

to within 150mV of the battery voltage. If the UVLO

comparator is tripped, the charger will not come out of

shutdown mode until VIN raises 150mV above the battery

voltage.

Automatic Recharge

The LP28056S constantly monitors the BAT pin voltage in

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

threshold (VRECHRG), another charge cycle begins and

current 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.

Power Dissipation

The conditions that cause the LP4056 to reduce charge

current through thermal feedback can be approximated by

considering the power dissipated in the IC. Nearly all of this

power dissipation is generated by the internal MOSFET—this

is calculated to be approximately:

PD=(VIN－VBAT) × IBAT

Where PD is the power dissipated, VIN is the input supply

voltage, VBAT is the battery voltage and IBAT is the charge

current. The approximate ambient temperature at which the

thermal feedback begins to protect the IC is:

TA=125℃-PDθJA

TA=125℃-(VIN-VBAT)×IBAT×θJA

VIN Bypass Capacitor

Many types of capacitors can be used for input bypassing;

however, caution must be exercised when using multilayer

ceramic capacitors. Because of the self-resonant and high Q

characteristics of some types of ceramic capacitors, high

voltage transients can be generated under some start-up

conditions, such as connecting the charger input to a live

power source. Adding a 1.5Ω resistor in series with an X5R

ceramic capacitor will minimize start-up voltage transients.

Layout Considerations



For the main current paths as indicated in bold lines,

keep their traces short and wide.



Put the input capacitor as close as possible to the device

pins (VIN and GND).



Connect all analog grounds to a command node and

then connect the command node to the power ground

behind the output capacitors.