Article Tools

• 

Designed for single-cell Li-ion/polymer batteries, the LT3650-4.1 and LT3650-4.2 monolithic, high-voltage battery chargers from Linear Technology Corp. come in a 9-mm² package. Their switch-mode architecture decreases power dissipation and uses little board space, according to Linear. With an operating range from 4.75 to 32 V, the devices also feature a 40-V maximum rating for extended system margin. Linear believes that the optional timer and C/10 termination eliminate the need for an external microcontroller and result in an uncomplicated design.

Another way the power devices save board space is through their integration on chip, says the company. Additionally, the charge current can be programmed and adjusted up to the limit of 2 A. External high-precision resistors are unnecessary in setting the float voltage, which economizes cost and space, states Linear.

Industrial handheld instruments, 12- to 24-V automotive and heavy equipment, desktop cradle chargers, and small notebook or tablet computers are some of the applications targeted by the two models. With a 4.1-V battery float voltage, the LT3650-4.1 permits a high-temperature safety margin, whereas the LT3650-4.2 boasts an optimized battery run time with a 4.2-V final charge voltage, according to Linear.

Small inductors and capacitors that can decrease noise and filtering needs are possible given the models’ 1-MHz frequency and current-mode architecture, the company asserts. Other details include the ±0.5% final float voltage accuracy, ±5% charge current accuracy, and ±2.5% C/10 detection accuracy.

A low-current standby mode switches on at a reduced input supply current of 85 µA after charging is complete. The input bias current falls to 15 µA when in shutdown mode as well. The battery uses less than 1 µA when it is not charging, which Linear believes extends the battery life.

The models also offer automatic restart, recharging, and preconditioning, a thermistor input for temperature-qualified charging, programmable input current limit, bad battery detection, and binary-coded status output pins. Two other features are the dynamic charge rate programming with a soft-start pin and an NTC resistor temperature monitor.

In a 0.75 mm, 12-pin, 3- by 3-mm dual flat no-lead (DFN) package, the two models can be sold in E and I grade versions that function from -40°C to +85°C. The E and I grades are available at $2.80 and $3.22, respectively, in quantities of 1000 pieces.