Buck converters integrate LDO regulators

Santa Clara, Calif. — Advanced Analogic Technologies Inc. (AnalogicTech) has unveiled a new family of high-voltage, high-current, non-synchronous step-down converters capable of providing high-efficiency power conversion from 24-V supplies.

Fabricated in AnalogicTech's proprietary high-voltage Modular BCD process, these new devices — the AAT1189, AAT2687 and AAT2689 — offer cost savings for wireless LAN, DSL and cable modem, and set-top-box designs by integrating a buck converter with a low noise, low dropout regulator (LDO).

Operating from an input voltage between 6.0 V and 24 V, the AAT1189 step-down converter is targeted at consumer electronics equipment operating from a low cost AC/DC adapter. It delivers up to 2.5-A output current. A 490-kHz switching frequency allows designers to use smaller filtering components for a small total solution size. The use of voltage mode control helps optimize performance across the entire load range.

The AAT2687 and AAT2689 devices combine a high-voltage step-down converter with a low-input voltage LDO regulator. The buck converters on both devices operate off a 6-V to 24-V input and deliver a VOUT of 1.5 V to 5.5 V. The buck converter for the AAT2689 delivers up to 2.5 A. For the AAT2687, the buck converter supplies up to 4.5 A. Like the AAT1189, the AAT2687 and AAT2689 take advantage of high-frequency switching to support the use of smaller external filtering components.

The AAT2687 and AAT2689 devices feature an LDO capable of delivering 600 mA. The LDO is said to offer low output noise, low quiescent current and excellent transient response. Separate enable pins allow the designer to independently control the buck converter and the LDO. Shutdown current is <15 uA. All three devices in the new product family feature internal soft start, over-temperature protection and adjustable over-current protection. The entire product family is qualified across the -40°C to +85°C temperature range.

Pricing: The AAT1189 is available in a Pb-free, 16-pin, 3 x 4-mm TDFN package and sells for $0.87. The AAT2689, available in a Pb-free, 16-pin 3 x 4-mm TDFN package, sells for $1.03. Available in a Pb-free, 24-pin, 4 x 5-mm TQFN package, the AAT2687 sells for $1.16. All in quantities of 1,000.
Product information: AAT1189, AAT2689, and AAT2687

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