Multi-Battery Operation Realized

October 14, 2014 – Linear Technology Korea (CEO Hong Sa-kwak, www.linear.com) announced the launch of the LTC4079, a 60V constant-current/constant-voltage 250mA multi-battery charger. This device's low quiescent current linear topology provides a simple inductor-free design and accommodates a wide input voltage range of 2.7V to 60V. The resistor-programmable 1.2V to 60V battery charging voltage range provides strict charging voltage accuracy of ±0.5% and onboard charge termination capability, making the LTC4079 suitable for numerous battery types including lithium-ion, nickel, and lead-acid. Charging current can be adjusted from 10mA to 250mA by providing an external resistor, and unlike competitor charger products, this device maintains high precision at low charging currents. Typical applications include embedded automotive and industrial systems, backup battery charging, energy harvesting, and thin-film battery products.

The LTC4079's input voltage regulation function can regulate the IN pin to a constant voltage above the battery or a constant differential voltage when charging from power-limited sources such as weak batteries or solar power. These functions can be used to prevent input voltage from collapsing below the UVLO voltage, or to maintain the input source voltage at the maximum power transfer point. Charging current decreases when input voltage drops below the programmed threshold. Through this regulation mechanism, charging current can be selected based on battery requirements and maximum available power at the charging input. Conversely, the LTC4079 manages situations when the input cannot provide the full programmed charging current.

The LTC4079's thermal regulation function ensures maximum charging current up to specified limits without overheating. Charging can be terminated via C/10 or an onboard adjustable timer. Other features include NTC thermistor temperature-authenticated charging, defective battery detection, automatic recharge with sample feedback in standby for negligible battery drain, and open-drain CHRG pin status output.

The LTC4079 provides a back metal pad for superior thermal performance and is available in a low-profile (0.75mm) 10-pin 3mm × 3mm DFN package. This device is available in E and I grades with an operating range of –40°C to 125°C. For E grade, it is priced at $2.35 per unit at quantities of 1,000. For detailed information, refer to www.linear.com/product/LTC4079.

Photo Caption: 60V, 250mA Linear Battery Charger

Product Features: LTC4079

• Wide input voltage range: 2.7V to 60V
• Adjustable multi-battery voltage: 1.2V to 60V
• Adjustable charging current: 10mA to 250mA
• Low quiescent current during charging: IIN = 4μA
• Low battery drain during shutdown and charging: IBAT < 0.01μA
• Automatic recharge
• Input voltage and differential voltage regulation for high impedance inputs
• Thermal regulation maximizing output current without overheating
• Constant voltage feedback with ±0.5% accuracy
• NTC thermistor input for temperature-authenticated charging
• Adjustable safety timer
• Charge status indicator
• 10-pin 3mm × 3mm DFN package with enhanced thermal performance