UB2421L-AG6-R datasheet(6/11 Pages) UTC

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UB2421

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 11

www.unisonic.com.tw

QW-R502-321.f



DESCRIPTION OF OPERATION

Normal Condition

The UB2421 monitors the voltage of the battery connected between VDD and VSS. The charge and discharge

scheme will be sensed by the voltage difference between VCSI and VSS.

When VODL<VDD<VOCU and VCH<VCSI<VOI1, UB2421 will turn on the charging (M2) and discharging (M1) control

MOSFETs. The charging and discharging processes can be operated normally.

Overcharge Condition

When the battery voltage becomes higher than the overcharge detection voltage (VOCU) during normal charging

condition through a delay time longer than TOC (the overcharge detection delay time), UB2421 will turn M2 off to stop

charging.

Release of Overcharge Condition

(1) When the battery is self discharging, and if VDD<VOCR and VOI1>VCSI>VCH occurs, M2 will be turned on and

back to normal condition.

(2) Remove the charger and connect UB2421 to a load. The discharging current will flow through the parasitic

diode of M2. At this moment, VCSI increases a voltage (VF) of the parasitic diode from the VSS level momentarily.

While VCSI>VOI1 and VDD<VOCU occur, M2 will be turns on and back to normal condition.

Over discharge Condition

When the battery voltage falls below the overdischarge detection voltage (VODL) during discharging condition

and through a delay time longer than TOD (the overdischarge detection delay time), UB2421 will turn M1 off to stop

discharging. In the meanwhile, CSI will be pulled up to VDD through an internal resistance.

If VCSI>VOI2, UB2421 will enter into power-down mode. While in this mode, the current consumption is lower

than 0.1μA.

Release of Power-down mode

After entering power-down mode, when the system is connected to a charger, the charging current will flow

through the parasitic diode of M1. If VCSI<VOI2 occurs, then UB2421 will release power-down mode. While keeping

charging status, there are two ways back to normal condition:

(1) If VCSI<VCH (Charger detection), then when VDD>VODL, M1 will be turned on and system will back to normal

condition.

(2) If VCH<VCSI<VOI2, the condition VDD>VODR, must be satisfied for M1 to be turned on, and then the system will

back to the normal condition.

Charger Detection

While connecting to a charger after entering into power-down mode, then if VDD<VCH, M1 will be turned on when

VDD>VODL. The system will back to normal condition since the charger has been detected.

Abnormal Charge Current Condition

When a charger is connected to the battery system in normal condition, then if VDD<VOCU and VCSI<VCH occur

through a delay time than TOC (delay time of overcharge detection), M2 will be turned off to stop this charging status,

which is abnormal charge current condition.

Abnormal charge current condition is released when the voltage of CSI pin becomes higher than charger

detection voltage (VCH), or the charger is removed.

Over Current (or Short Circuit ) Condition

When the current is too large during discharging under normal condition as a result of the voltage detected by

CSI is greater than VOI1 (or VOI2) through a delay time TOI1 (or TOI2), it satisfies the over current (or short circuit)

condition. Then M1 will be turned off and CSI will be pulled down to VSS through an internal resistance. It is called the

over current (or short circuit) condition.

(1) If the over current (or short circuit) is detected and it keeps longer than the overdischarge detection delay

time with the same circumstance, the condition will be changed to the power-down mode when the battery voltage

falls below the overdischarge detection voltage.

(2) If the battery voltage falls below the overdischarge detection voltage (VODL) due to the over current (or short

circuit), the discharging control M1 will be turned off when this condition occurs. After overdischarge detection delay

time (TOD) expired, if the battery voltage is still equal to or lower than the overdischarge detection voltage, the

condition will be changed to power-down mode.

UB2421L-AG6-R Datasheet(PDF) 6 Page - Unisonic Technologies

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