HM5904 datasheet(11/15 Pages) HMSEMI

11 / 15 page

Charge Termination

A charge cycle is terminated when the charge current falls to 1/10 the programmed value after

the final float voltage is reached. The charge current is shut off and the HM5904 enters standby mode,

where the input supply current drops to 55uA. The HM5904 draws very few current from the battery in

standby mode. This feature reduces the charge and discharge cycles on the battery, further prolong

the battery life.

Thermal Protection when charging

An internal thermal feedback loop reduces the fixed charge current if the die temperature rises

above a preset value of approximately 100°C. This feature protects the HM5904 from excessive

temperature and allows the user to push the limits of the power handing capability of a given circuit

board without risk of damaging the HM5904 . The charge current can be set according to typical

ambient temperature with the assurance that the charge will automatically reduce the current in worst

case condition.

VIN 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 500mV. Furthermore, to protect against reverse current in the power MOSFET, the

UVLO circuit force the HM5904 to enter shutdown mode if VIN falls to within 10mV of the battery voltage.

If the UVLO comparator is tripped, the charger will not come out of shutdown mode until VIN rises

100mV above the battery voltage.

Automatic Recharge

Once the charge cycle is terminated, the HM5904 continuously monitors the voltage on the BAT

pin using a comparator with a 0.8ms filter time (TRECHARGE). 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 eliminated the need for periodic

charge cycle initiations. CHRGB output enters a strong pull-down state during recharge cycles.

HM5904 Datenblatt(PDF) 11 Page - Shenzhen Huazhimei Semiconductor Co., Ltd