Features

Design offline charger design for single battery lithium -ion batteries

The first -side controller provides control feedback

powerful battery insertion and removal detection

The voltage adjustment feedback to the first side to achieve high -precision charging

Termid charging at the minimum current and time

Pre -charging regulator with a security timer

The charging status output indicator of the LED or host processor interface is in the middle, charging and failure situation

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Temperature monitoring before and during charging

Short -circuit protection

#8226 TS1; Small Packaging

Application

Digital camera stent charger

[[ 123] Desktop charger

Handheld Equipment

Instructions

BQ24901 Lithium ion charging management equipment is special Design offline charger application. BQ24901 is located on the secondary side of the transformer to provide control feedback to various first -side controller. BQ24901 provides current or voltage adjustment feedback, temperature monitoring, charging status and adjustable charging terminals, in a single single -chip device. Without the completion of the battery or charging, the BQ24901 continuously adjusts the secondary voltage and is used as a VCC power supply for the device.

The characteristics of the cell depth to the 24BQ stage. The pre -adjustment phase is achieved through the secondary linear adjustment. After pre -processing, BQ24901 adjusts the charging current to the value of the external current detection resistor settings. Once the battery reaches the charging voltage, the voltage adjustment loop is taken over and completed the charging cycle. The pressure regulation accuracy is better than ± 30mv. Terminal charging according to the minimum current. The minimum current level is set through the TADJ pin. The internal charging timer provides backup for charging.

BQ24901 is designed for reliably detecting the insertion and removal of the battery, including a battery pack with an open protector. Other standard functions include the charging function activated when the battery voltage is lower than the VRCH threshold. In addition to the standard function, BQ24901 mentionedBattery temperature monitoring and state display. The temperature sensing circuit uses an external thermistor to continuously measure the battery temperature and stop charging until the battery temperature is within the threshold range of the user definition. The STAT pin indicates the working status of the charger. These outputs can be used to drive the interface of LED or host micro -controllers.

Function box diagram

Application information

BQ24901 supports the accurate current and voltage adjustment of a lithium ion charging system suitable for single batteries. Figure 1 shows a typical application diagram, Figure 2 shows a typical charging overview, and Figure 3 shows an operating flowchart.

Charging confirmation and pre -processing BQ24901 starts charging cycles when there is battery. Charging confirmation is based on battery temperature and voltage. If the battery temperature is from VLTF to VHTF, the device will be suspended and waiting for the battery temperature to be within the allowable range. The device also checks the battery voltage. If the battery voltage is lower than the low voltage threshold Vlowv, the device uses a pre -regulating current IPRECHG to charge the battery.

Temperature sensing (TS) input

BQ24901 continuously monitor the battery temperature by measuring the voltage between the TS pin and the VSS. The negative temperature coefficient thermistor (NTC) and external compressors usually generate this voltage. BQ24901 compares this voltage with its internal threshold to determine whether the charging is allowed. When starting the charging cycle, the battery temperature must be within VLTF to VHTF threshold range. If the battery temperature exceeds this range, the device will be suspended and the battery temperature will wait for the battery temperature to be within the range of VLTF to VHTF. During the charging cycle (pre -charging and fast charging), the battery temperature must be within the threshold range of VLTF to VTCO. If the battery temperature exceeds this range, BQ24901 will be suspended and waited until the battery temperature is within the range of VLTF to VHTF. The device is closed by closing the CC pin and keeping the timer value (that is, the timer is not reset at the pause state).

FIG. 4 summarizes this operation.

VCC regulations

Under the following conditions, BQ24901 adjusts the VCC power supply, and the device is activated. The VCC regulating loop compensation is implemented by the SCOMP pin.

*No battery status

*Pre -charging

*Charging pause

*Failure

*Complete

Voltage monitoring and adjustment

Voltage adjustment feedback pass BAT. The input is directly connected to the positive electrode of the battery pack.

ElectricityThe compensation of the regulating circuit is achieved through the VCOMP pin.

Current Regulations

BQ24901 provides current adjustment when the battery pack voltage is lower than the adjustment voltage VREG. The device monitors the charging current of the SNS input end through the voltage of the external sensing resistance RSNS connected to the battery pack. The charge current feedback is maintained through the SNS application of the pin, and the adjustment of the VSNS threshold is maintained. The formula of the formula in the formula (1) calculates the value of the sensing resistance.

Among them: i (CHG) is the required charging circuit

current adjustment loop compensation to pass the Icomp pin.

The current adjustment of the slope rising and decreased

When the transition from the pre -charging to the rapid charging, and entering and exiting the fault/pause mode, the two current adjustment circuits will rise and decrease. At this time, at this time, at this time, at this time, at this time LDO requires hard switch. Figure 5 shows a typical step ramp.

Battery plug -in detection

BQ24901 reliably detects the insertion and removal of the battery pack in various cases. This includes a battery pack with an open or closed protector. Figure 6 shows the flowchart. Table 1 summarizes the insertion and disassembly conditions of various batteries.

Charging termination and rechargement

BQ24901 monitor charging current during voltage adjustment. When the current is gradually reduced to the charging termination of the current detection threshold, the device declares the condition and the charging is terminated. The charging side is set up through the TADJ pin, as shown in Table 2 and Figure 7.

BQ24901 also has two internal digital filters used to detect the termination threshold. Digital filters with Ttermdet1 and Ttermdet2 response time aim to reduce possibilities or switching frequency noise at the end of the line or switch frequency noise.

When one of the following conditions is detected, a new charging cycle will be started:

1. The battery voltage is lower than the VRCH threshold; 2. New battery insertion (once the battery is Below VRCH threshold);

3. Power -power reset (POR).

Charging timer

BQ24901 offers two charging timers to protect batteries during the pre -charging and charging phase. The first timer T30min was reset at the beginning of the new charging cycle and started during the pre -charging phase. During the pre -charging process, if the timer expires before the battery rises to Vlowv threshold, the failure will be notified. Power -powered resetting or replacing the battery clearance failure.

The second timer T5HR was reset at the beginning of the new charging cycle and started at the beginning of the charging phase. If you areDuring the charging process, the battery current fails to reach the charging terminal detection threshold itm, and the fault will be notified.Power -powered resetting or replacing the battery clearance failure.

Charging status shows

Open drain STAT1 and STAT2 output indicate various charger operations, as shown in Table 3.

Mechanical data

PW (R-PDSO-G **) Plastic small shape packaging

Note: A. All linear size units are millimeters.

B. This drawing will not be notified separately if there is any change.

C. The main size does not include mold flying or protruding objects with no more than 0.15.

D. It belongs to Jedec Mo-153.