DALLAS Texas Instruments Inc. touts its highly integrated IC for single-cell lithium-ion batteries, the UCC3952A, as the first battery protector of its kind to meet the size requirements for emerging 4-mm cell phone batteries.
The chip's integrated MOSFET switch also makes it ideal for applications in any equipment powered by a one-cell Li-ion or lithium polymer battery, the company said. These include cordless phones, personal digital assistants and pagers.
The UCC3952A protects batteries from overcharge, overdischarge, overcurrent and excessive thermal conditions. Unlike competitive solutions that require a handful of additional parts-controller, separate MOSFET, thermal fuse, and four or five resistors and capacitors-the TI device needs a single 0.1-microfarad surface-mount capacitor. TI said that translates into a space reduction of up to 75 percent.
With its own 50-milliohm MOSFET switch and thermal shutdown, the device enables designers to easily reduce the size, cost and parts count of the complete protection circuit while increasing reliability, according to TI.
The UCC3952A is available in the smallest package for a device of its kind, an 18-pin bump chip carrier (BCC) that measures 3.4 x 4.55 mm. As a result, the complete protection circuit occupies 25 square millimeters, compared with as much as 120 mm2 for competitive solutions.
This BiCMOS chip draws 5 microamps of supply (operating) current, handles up to 3 A and comes in four standard overvoltage protection levels, from 4.2 to 4.35 V. A precision bandgap reference continuously monitors the cell voltage, and both overcharge and overdischarge voltage limits are precision-trimmed to prolong battery life.
In operation, the UCC3952A opens its MOSFET switch to protect the cell from damage when its on-chip logic detects an over- or undervoltage condition. When the battery is in an overcharge state, a patented feedback loop allows discharge current to flow; charge current flows during an overdischarge state. In addition, an on-chip current-sense resistor detects short-circuits, turning off the MOSFET switch when appropriate. The device has a delay built into the overcurrent protection circuit that permits charging of capacitive loads.
An on-chip shutdown circuit provides thermal protection, and an on-chip charge pump cuts power losses when charging or discharging a low-cell-voltage battery pack.
The UCC3952A itself withstands up to 18 V, making it sturdy enough to survive the higher voltages common in automotive systems. The device is also protected against reverse-voltage connections.
Available in threshold voltages of 4.2, 4.25, 4.3 and 4.35 V, the UCC3952A will be offered as samples in September. Volume production is planned for October.
Suggested resale pricing starts at $1.99 each in quantities of 1,000.
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EETInfo No. 624