Milpitas, Calif. - Linear Technology says its LTC4059, for single-cell lithium-ions, will fast-charge without any risk of system overheating. It can also be configured as a constant-current source for charging NiMH/NiCd batteries. The linear charger, in a 2-by-2 mm DFN package, requires only two discrete components (input capacitor and resistor for programming charge current), versus the usual five that commonly include an external MOSFET, current-sense resistor and reverse-current blocking diode. The DFN takes half the fooprint of a SOT-23 and, according to the company, offers up to 60°C/W lower thermal resistance. With proper PCB layout design, the LTC4059 will safely deliver up to 900 mA (±5 percent accuracy) at 4.2 volts (to within 0.6 percent) to charge a lithium-ion cell from a nominal 5-volt input, with the chip's thermal-regulation circuitry automatically reducing charge current as required during high ambient-temperature conditions. This charger contains a current-monitor output, suitable for microprocessor charge-termination and control, that delivers a voltage proportional to the charge current.
The LTC4059 is rated for operation over the range of -40 to +85°C. It's priced at $1.35 each in 1k quantities.