I²C Controllable Buck Regulator with Two LDOs in a 4mm × 4mm QFN

The LTC3445 contains a high efficiency monolithic synchronous current mode buck regulator, two LDO regulators, a PowerPath™ controller and an I2C™ interface.

The buck regulator has a 6-bit programmable output range of 0.85V to 1.55V. Also, the buck regulator uses either a constant (1.5MHz) or a spread spectrum switching frequency. Using the spread spectrum option allows for a lower noise regulated output as well as low noise at the input. In addition, the regulated output voltage slew rate is programmable via the I2C interface.

The LTC3445 contains two LDO voltage regulators. The regulator output voltages are externally resistor programmable. Each LDO is capable of delivering up to 50mA.

The LTC3445 contains control circuitry (PowerPath) for automatic back-up battery selection. VBACKUP is typically a coin cell.

Typical supply current during operation is only 360µA and drops to 27µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3445 ideal for single Li-Ion battery-powered applications. Automatic Burst Mode® operation increases efficiency at light loads, further extending battery life.

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, Spread Spectrum patent pending.

Applications

* Intel’s Microprocessor Supply (PXA27X)

* Portable Instruments

* High Efficiency: Up to 93%

* 600mA Output Current (VCC1 = 3V, VOUT = 1.3V)

* Programmable Output Voltage: 0.85V to 1.55V

* 2.5V to 5.5V Input Voltage Range

* 1.5MHz Constant Frequency or Spread Spectrum Option

* Soft-Start