LTC3445 I2C Controllable Buck Regulator with Two LDOs in a 4mm × 4mm QFN UFEATURESDESCRIPTIOBuck Regulator The LTC®3445 contains a high efficiency monolithic syn- ■ High Efficiency: Up to 93% chronous current mode buck regulator, two LDO regula- ■ 600mA Output Current (VCC1 = 3V, VOUT = 1.3V) tors, a PowerPathTM controller and an I2CTM interface. ■ Programmable Output Voltage: 0.85V to 1.55V The buck regulator has a 6-bit programmable output range ■ 2.5V to 5.5V Input Voltage Range of 0.85V to 1.55V. Also, the buck regulator uses either a ■ 1.5MHz Constant Frequency or Spread Spectrum constant (1.5MHz) or a spread spectrum switching fre- Option quency. Using the spread spectrum option allows for a ■ Soft-Start lower noise regulated output as well as low noise at the LDOs input. In addition, the regulated output voltage slew rate is ■ Two LDO Regulators: 0.3V Dropout at 50mA programmable via the I2C interface. PowerPath Controller The LTC3445 contains two LDO voltage regulators. The ■ Dynamically Regulates VCC BATT regulator output voltages are externally resistor program- I2C mable. Each LDO is capable of delivering up to 50mA. ■ Standard (100kHz) or Fast Mode (400kHz) ■ 24-Lead (4mm × 4mm) QFN Package The LTC3445 contains control circuitry (PowerPath) for automatic back-up battery selection. VBACKUP is typically U a coin cell. APPLICATIO S Typical supply current during operation is only 360µA and ■ Intel’s Microprocessor Supply (PXA27X) drops to 27µA in shutdown. The 2.5V to 5.5V input ■ Portable Instruments voltage range makes the LTC3445 ideal for single Li-Ion , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. battery-powered applications. Automatic Burst Mode® PowerPath is a trademark of Linear Technology Corporation. I2C is a trademark of Philips Electronics N.V. operation increases efficiency at light loads, further ex- Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, tending battery life. 6611131, Spread Spectrum patent pending. UTYPICAL APPLICATIO VCC Efficiency and Power Loss VBACKUP vs Load Current, V 4.7µF CC1 = 3.6V CER V V 20k CC1 CC2 VCC1 100 1000 V BATTFAULT nBATT_FAULT TRACK V 90 3V BACKUP EFFICIENCY V COIN + V 3V BACKUP CC BATT TYP 4.7µF 80 CELL CER DAC MAX DAC MIN 100 POWER LOSS (mW) 2.2µH 70 0.85V PWR_EN RUN SW 60 4.7µF TO 1.55V SDA FB CER 50 10 LTC3445 I2C BUS DAC MAX DAC MIN SCL LDO1 1.3V 40 VCC 705k 604k 10µF EFFICIENCY (%) CER 30 V POWER LOSS 1.0 CC1 OR GND ADD7 LDO1FB 20k 20 VCC1 OR GND ADD6 LDO2 1.1V 10 nV PGOOD CC_FAULT 503k 604k 10µF CER 0 0.1 GND LDO2FB 0.1 1 10 100 1000 3445 TA01 LOAD CURRENT (mA) 3445 TA01b 3445fa 1
