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[FAQ] BQ2407x and BQ2423x: Frequently asked Questions

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Part Number: BQ24074

Q: Why is my device not charging?

A: Things that could prevent the charger from charging the battery include /CE pin not being low, the TS voltage not being between 0.3 V and 2.1 V, having the load current as high as the input current limit can cause the device to go into supplement mode.

Q: My charging current is lower than expected

A: Ensure the device is not in thermal regulation which will reduce the charge current. Remove the load on the OUT pin to reduce the power dissipated in the IC. Measure the IN and OUT voltage to ensure the device is not in VIN-DPM or DPPM mode respectively. The charge current will be reduced if either of these modes are active. For more details on VIN-DPM and DPPM, see Dynamic Power Path Management and Dynamic Power Management.

Q: Why does my output shutoff when more than 3A from OUT on the BQ2407x?

A: The device has OUT short detection which turns off the FET between BAT and OUT when the short circuit is asserted. This happens when VBAT - VOUT > Vo(Ssc2), which is typically 250 mV. The voltage drop across the FET is due to the RDSON which is typically 50 mΩ.

Q: Can I reduce my NTC Hot trip point from 50°C to 45°C

A: Using external resistors and equation 8 in the BQ2407x Standalone 1-Cell 1.5-A Linear Battery Charger with PowerPath Data Sheet, the range can be expanded but not reduced on the BQ2407x devices. The BQ2407xT offers this flexibility.

Q: When is DPPM and VIN-DPM available?

A: VIN-DPM is only available when in either USB-100 or USB-500 mode with the input voltage input being monitored. DPPM is always available with the OUT voltage being monitored. If the input or charge current is being reduced in ILIM mode, this will be due to DPPM mode so the OUT voltage should be checked.

Q: What happens if i set my charge current higher than my input current limit?

A: The battery will be charge at the rate of the input current limit as long as there is no load on OUT.

Q: Why do i see 0V on TS pin with a resistor on TS?

A: Check to make sure there is no short on the pin. After that, check to make sure you have the BQ2407x and BQ2407xT.

Q: What is the difference between the BQ2407x and BQ2407xT family of devices?

A: The BQ2407x devices have a current based NTC monitoring while the BQ2407xT has a voltage based NTC monitoring that requires a pullup to a voltage source.

Q: Does the BQ2407x family have BUVLO?

A: The devices don't have BUVLO. Protection will need to be added to prevent over-discharge of the battery.

Q: Should I be worried about current leaking from BAT or OUT to the IN pin?

A: There are 2 back to back FETs on the input with backgate control to prevent against this.

Refer to the Application Note below for more information.

https://www.ti.com/lit/an/slua947a/slua947a.pdf

Regards,

Sharafadeen Raheem

Applications Engineer

Battery Chargers

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