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Power Supply ICs and Controllers
News Release from: Texas Instruments (April 2006-) | Subject: bq24314, bq24316 and bq24300 ICs
Edited by the Electronicstalk Editorial
Team on 06 September 2007
Circuits protect portable devices
Texas Instruments' bq24314 adds extra protection to a lithium battery when a charger circuit fails due to a fault condition.
Texas Instruments has released battery charger front-end integrated circuits which dramatically increases protection when charging a mobile phone or other portable electronic device The 2 x 2mm safety circuits protect a system from input over-voltage, over-current and battery over-voltage conditions, which may result from a power spike during charging or a defective or incorrect wall adapter
This article was originally published on Electronicstalk on 4 Apr 2006 at 8.00am (UK)
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"Adding power protection to a handheld device helps safeguard end users against accidental fault conditions, which reduces the number of customer end-equipment returns", said Masoud Beheshti, Director of TI's Battery Charge Management business.
"This charger front-end circuit provides three solid levels of protection to provide the maximum amount of safety when charging a handheld device".
The first member of TI's new bq243xx family of charger front-end circuits with integrated FETs, the bq24314, adds extra protection to a lithium battery when a charger circuit fails due to a fault condition.
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The protection IC can report the status of the fault to the host processor, such as TI's DM355 processor or an application processor from the OMAPT 3 product family, allowing the host processor to apply additional corrective actions.
Input over-voltage conditions are caused by steady-state or transient voltage events, such as "hot-plugging" a charged adapter, using a nonregulated or incorrect adapter, or load transients.
Any of these events can increase or "spike" the voltage applied to the device and potentially damage the host system.
The bq24314 detects the over-voltage level and effectively disconnects the input to the charger to protect the device.
The device features an input over-voltage threshold of 5.85V.
Another version of the circuit, the bq24316, supports up to 6.8V.
Input over-current conditions can occur in integrated power management devices that incorporate a battery charger, which have a direct connection from the input to the system's bus voltage.
Often there is no protection from pulling excessive current from the adapter to the system.
The programmable bq24314 limits the input current by sensing and regulating its integrated Mosfet to ensure the system does not pull an excessive amount of current.
Potential hazardous events may occur if single-cell, Li-Ion and Li-Polymer batteries are over-charged beyond their float voltage - typically around 4.2 V.
Because of this, portable designers generally seek redundant safety measures to ensure battery safety and compliance.
The bq24314 offers a second level of protection that helps monitor the battery's voltage, and if an over-voltage is detected, interrupts the input charging source.
The bq24314 and bq24316 come in an eight-pin, 2 x 2mm small-outline, no-lead (SON) package.
In the fourth quarter of 2007, TI plans to introduce the bq24300 charger front-end protection ICs.
Featuring a fixed input over-current protection threshold of 300mA, and input over-voltage protection threshold at 10.5 V, the bq24300 devices target low-power applications, like Bluetooth headsets.
The bq24300 acts as a linear regulator by managing the output to 5.5V (or 4.5V with the bq24304) for voltages up to the input over-voltage threshold.
Additionally, a bq24300 circuit can protect against reverse polarity caused by a faulty adapter using an optional external P-channel Mosfet.
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