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Sub-1µA shunt IC charger protects Li-ion cells

Posted: 22 Feb 2010     Print Version  Bookmark and Share

Keywords:Li-Ion cells  shunt battery charger  polymer cells 

Shunt battery charger IC

From Linear Technology Corp. comes the LTC4070, an easy-to-use, tiny shunt battery charger system IC for Li-Ion/Polymer batteries packs an internal thermal battery conditioner that reduces the float voltage to protect the cells at elevated battery temperatures. Its 450nA operating current, charges and protects batteries from previously unusable very low current, intermittent or continuous charging sources.

The LTC4070's charge current may be boosted from 50mA up to 500mA with the addition of an external PMOS shunt device. Multiple-cell battery stacks can be charged and balanced by configuring several LTC4070s in series. Housed in a low profile (0.75mm) 8-lead 2mm x 3mm DFN package, the LTC4070 provides a complete and ultra-compact charger solution with only a single external resistor required in series with the input voltage. The device's feature set is well suited for continuous and intermittent, lower power charging source applications, including Li-ion/polymer battery backup, thin film batteries, coin cell batteries, memory backup, solar-powered systems with backup, embedded automotive and energy scavenging/harvesting.

With pin-selectable settings of 4V, 4.1V, or 4.2V, the LTC4070's 1 per cent accurate battery float voltage allows the user to optimise the balance between battery capacity and lifetime. Independent low battery and high battery supervisory status outputs indicate a discharged or fully charged battery. In conjunction with an external PFET in series with the load, the low battery status output enables a latch-off function that automatically disconnects the system load from the battery to protect the battery from deep discharge.

In addition to its compact thermally enhanced 2mm x 3mm 8-lead DFN package, the LTC4070 is also offered in an 8-lead MSOP package. The devices are rated for operation from -40°C to 125°C. Pricing starts at Rs.95.12 ($2.06) and Rs.106.67($2.31) each in 1,000-piece quantities for both packages, in E and I grades, respectively

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