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UB261 Datasheet(PDF) 5 Page - Unisonic Technologies |
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UB261 Datasheet(HTML) 5 Page - Unisonic Technologies |
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. |
Similar Part No. - UB261_15 |
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Similar Description - UB261_15 |
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