High voltage step-down switched capacitor converter

The LTC3255 produces a regulated output (2.4V to 12.5V adjustable) from a wide 4V to 48V input that is +60V/-52V tolerant. At no load, Burst Mode operation reduces V_IN quiescent current to 16µA, and 2:1 capacitive charge pumping extends output current capability to approximately twice the input current. The LTC3255 is well suited for a variety of applications such as industrial control, factory automation, sensors and supervisory control and data acquisition systems, housekeeping power supplies, plus current-boosting voltage regulators for 4mA to 20mA current loops.

The LTC3255 operates either as a general purpose step-down charge pump with 2:1 or 1:1 conversion ratios, or it can operate as a current doubling shunt regulator. In normal mode, the conversion ratio is chosen based on V_IN, V_OUT, and load conditions, and switching between conversion modes is automatic. In shunt mode, the device is forced into 2:1 mode, enabling the LTC3255 to provide a regulated output voltage from a current source input with nearly two times the input current available at the load. For example, this feature enables a 4mA current loop to power a 7.4mA load continuously with a 3.3V regulated output voltage. The LTC3255 withstands reverse-polarity input supplies down to -52V and output short-circuit without damage. Safety features, including an output current limit and over-temperature protection further enhance robustness.

The LTC3255 is available in a low-profile (0.75mm) 3mm x 3mm 10-lead DFN and a 10-lead MSOP package, both with a backside metal pad for enhanced thermal performance. The E- and I-grade operating junction temperature is -40°C to +125°C. The H grade offers -40°C to +150°C operation and the high reliability MP grade is specified from -55°C to +150°C. 1000-piece pricing for the E grade starts at $2.30 each, and devices are available from stock.

Key features:

• Input Voltage Range: 4V to 48V,
• Adjustable Regulated Output: 2.4V to 12.5V, 50mA Maximum,
• 16µA Quiescent Current in Regulation at No Load,
• Reverse-Polarity Input Protection to –52V,
• Multimode Charge Pump (2:1, 1:1) with Automatic Mode Switching Maintains Regulation over Wide V_IN Range,
• Input Voltage Shunt Mode for Current-Fed Applications,
• Power Good Output,
• Over-Temperature & Short-Circuit Protection,
• Operating Junction Temperature: 150°C Maximum,
• Thermally Enhanced 10-Lead MSOP & 10-Lead (3mm × 3mm) DFN Packages.