UB261G-AB-AG6-R datasheet(5/10 Pages) UTC

5 / 10 page

UB261

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

5 of 10

www.unisonic.com.tw

QW-R502-A27.b



OPERATION

1. Normal Condition

The UTC UB261 series monitors the voltage of the battery connected between VDD pin and VSS pin and the

voltage difference between VM pin and VSS pin to control charging and discharging. When the battery voltage is in

the range from the overdischarge detection voltage (VDL) to the overcharge detection voltage (VCU), and the VM pin

voltage is in the range from the charger detection voltage (VCHA) to the overcurrent 1 detection voltage (VIOV1), the IC

turns both the charging and discharging control FETs on. This condition is called the normal condition, and in this

condition charging and discharging can be carried out freely.

Note: When a battery is connected to the IC for the first time, discharging may not be enabled. In this case, short

the VM pin and VSS pin or connect the charger to restore the normal condition.

2. Overcurrent Condition

When a battery in the normal status is in the status where the voltage of the VM pin is equal to or higher than the

overcurrent detection voltage because the discharge current is higher than the specified value and the status lasts

for the overcurrent detection delay time, the discharge control FET is turned off and discharging is stopped. This

status is called the overcurrent status. In the overcurrent status, the VM and VSS pins are shorted by the resistor

between VM and VSS (RVMS) in the IC. However, the voltage of the VM pin is at the VDD potential due to the load as

long as the load is connected. When the load is disconnected, the VM pin returns to the VSS potential. This IC detects

the status when the impedance between the EB+ pin and EB- pin (Refer to the typical application circuit) increases

and is equal to the impedance that enables automatic restoration and the voltage at the VM pin returns to overcurrent

detection voltage 1 (VIOV1) or lower and the overcurrent status is restored to the normal status.

Note: The impedance that enables automatic restoration varies depending on the battery voltage and the set value

of overcurrent 1 detection voltage.

3. Overcharge Condition

When the battery voltage becomes higher than the overcharge detection voltage (VCU) during charging under the

normal condition and the detection continues for the overcharge detection delay time (tCU), the UTC UB261 series

turns the charging control FET off to stop charging. This condition is called the overcharge condition. The overcharge

condition is released by the following two cases:

(1) When the battery voltage falls below the overcharge release voltage (VCL), the UTC UB261 series turns the

charging control FET on and turns to the normal condition.

(2) When a load is connected and discharging starts, the UTC UB261 series turns the charging control FET on

and returns to the normal condition. Just after the load is connected and discharging starts, the discharging current

flows through the parasitic diode in the charging control FET. At this moment the VM pin potential becomes Vf, the

voltage for the parasitic diode, higher than VSS level. When the battery voltage goes under the overcharge detection

voltage (VCU) and provided that the VM pin voltage is higher than the overcurrent 1 detection voltage, the UTC

UB261

series releases the overcharge condition.

Note 1: If the battery is charged to a voltage higher than the overcharge detection voltage (VCU) and the battery

voltage does not fall below the overcharge detection voltage (VCU) even when a heavy load is connected, the

detection of overcurrent 1, overcurrent 2 and load shortcircuiting do not function until the battery voltage falls below

over charge detection voltage (VCU). Since an actual battery has an internal impedance of several dozens of mΩ, the

battery voltage drops immediately after a heavy load that causes overcurrent is connected, and the detection of

overcurrent 1, overcurrent 2 and load short-circuiting function.

Note 2: When a charger is connected after the overcharge detection, the overcharge condition is not released

even if the battery voltage is below the overcharge release voltage (VCL). The overcharge condition is released when

the VM pin voltage goes over the charger detection voltage (VCHA) by removing the charger.

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