HM4055AMR datasheet(13/16 Pages) HMSEMI

13 / 16 page

Page 13

In the thermal regulation, this action of transporting current to battery will raise. One of the measure is through an

external component(as a resistor or diode) to consume some power dissipation.

For example: The HM4055 with 5V supply voltage through programmable provides full limiting current 800mA

to a charge lithium-ion battery with 3.75V voltage. If JA is 105℃/W, so that at 25℃ ambient temperature, the charge

current is calculated to be approximately :

BAT

110℃ - 25℃

(Vs -I

*Rcc - V )* θ

In order to increase the thermal regulation charge current, can decrease the power dissipation of the IC through

reducing the voltage (as show fig.3) of both two ends of the resistor which connecting in series with a 5V AC adapter.

With square equation to calculate IBAT ：

BAT

4Rcc(110℃ - T )

(Vs - V )- (Vs - V ) -

2Rcc

If RCC=0.25Ω, VS=5V, VBAT=3.75V, TA=25℃ and JA =105℃/W, we can calculate the thermal regulation charge

current: IBAT＝764mA. It means that in this structure it can output 800mA full limiting charge current at more high

ambient temperature environment.

Although it can transport more energy and reduce the charge time in this application, but actually spread charge

time, if HM4055 stay in under-voltage state, when VCC becomes too low in voltage mode. Fig.4 shows how the

voltage reduced with increase RCC value in this circuit. This technique will act the best function when in order to

maintain the minimize the dimension of the components and avoid voltage decreased to minimize RCC .

Fig.3:A circuit to maximum the thermal

Fig.4:The relationship curve between charge

regulation charge current

current with RCC

VCC 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 a ceramic capacitor will minimize start-up voltage

HM4055

HM4055A

HM4055AMR Datasheet(PDF) 13 Page - Shenzhen Huazhimei Semiconductor Co., Ltd