Datasheet LTC3445 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | I²C Controllable Buck Regulator with Two LDOs in a 4mm × 4mm QFN |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTIO. Buck Regulator. LDOs. PowerPath Controller. I2C. … |
| File Format / Size | PDF / 486 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. Buck Regulator. LDOs. PowerPath Controller. I2C. APPLICATIO S. TYPICAL APPLICATIO. Efficiency and Power Loss
Model Line for this Datasheet
Text Version of Document
LTC3445 I2C Controllable Buck Regulator with Two LDOs in a 4mm × 4mm QFN
U FEATURES DESCRIPTIO Buck 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.
U TYPICAL 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
U FEATURES DESCRIPTIO Buck 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.
U TYPICAL 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
