Maker : National Semiconductor
Part No. : LM3370

  Datasheet PDF : LM3370.pdf
  Cross Reference : LM3370 Cross Reference
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Product Information

LM3370 Dual Synchronous Step-Down DC-DC Converter with Dynamic Voltage Scaling Function January 4, 2008 LM3370 Dual Synchronous Step-Down DC-DC Converter with Dynamic Voltage Scaling Function General Description The LM3370 is a dual step-down DC-DC converter optimized for powering ultra-low voltage circuits from a single Li-Ion battery and input rail ranging from 2.7V to 5.5V. It provides two outputs with 600 mA load per channel. The output voltage range varies from 1V to 3.3V and can be dynamically controlled using the I2C compatible interface. This dynamic voltage scaling function allows processors to achieve maximum www.DataSheet4U.com lowest power level. The I2C compatible performance at the interface can also be used to control auto PFM-PWM/PWM mode selection and other performance enhancing features. The LM3370 offers superior features and performance for portable systems with complex power management requirements. Automatic intelligent switching between PWM lownoise and PFM low-current mode offers improved system efficiency. Internal synchronous rectification enhances the converter efficiency without the use of further external devices. There is a power-on-reset function that monitors the level of the output voltage to avoid unexpected power losses. The independent enable pin for each output allows for simple and effective power sequencing. LM3370 is available in a 4 mm by 5 mm 16-lead non-pullback LLP and a 20-Bump micro SMD, 3.0 mm x 2.0 mm x 0.6 mm, package. A high switching frequency—2 MHz (typ)—allows use of tiny surface-mount components including a 2.2 µH inductor. Default fixed voltages for the 2 output voltages combination can be customized to fit system requirements by contacting National Semiconductor Corporation. Features ■ I2C compatible interface — VOUT1 = 1V to 2V in 50 mV steps — VOUT2 = 1.8V to 3.3V in 100 mV steps — Automatic PFM/PWM mode switching & Forced PWM mode for low noise operation — Spread Spectrum capability using I2C 600 mA load per channel 2 MHz PWM fixed switching frequency (typ.) Internal synchronous rectification for high efficiency Internal soft start Power-on-reset function for both outputs 2.7V ≤ VIN ≤ 5.5V Operates from a single Li-Ion cell or 3 cell NiMH/NiCd batteries and 3.3V/5.5V fixed rails 2.2 µH Inductor, 4.7 µF Input and 10 µF Output Capacitor per channel 16-lead LLP Package (4 mm x 5 mm x 0.8 mm) 20-Bump micro SMD Package (3.0 mm x 2.0 mm x 0.6 mm) ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Applications ■ ■ ■ ■ Baseband Processors Application Processors (Video, Audio) I/O Power FPGA Power and CPLD Typical Performance Curve 20167379 Dimensions: 3.0 mm x 2.0 mm x 0.60 mm 20167381 Efficiency vs. Output Current, VOUT1= 1.2V © 2008 National Semiconductor Corporation 201673 www.national.com LM3370 Typical Application www.DataSheet4U.com 20167301 FIGURE 1. Typical Application Circuit Functional Block Diagram 20167302 FIGURE 2. Functional Diagram www.national.com 2 LM3370 Package Marking Information 16-Lead LLP Package 20167343 FIGURE 3. Top Marking www.DataSheet4U.com 20167342 FIGURE 4. Top View Pin Descriptions (LLP) Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Name VIN2 SW2 PGND2 VDD SGND PGND1 SW1 VIN1 FB1 SDA SCL nPOR1 nPOR2 EN1 EN2 FB2 Buck 2 Switch Pin Buck 2 Power Ground Signal supply voltage input, VDD must be equal or greater of the two inputs (VIN1 & VIN2) Signal GND Buck 1 Power Ground Buck 1 Switch Pin Power supply voltage input to PFET and NFET switches for Buck 1 Analog Feedback Input for Buck 1 I2C Compatible Data, a 2 kΩ pull up resistor is required I2C Compatible Clock, a 2 kΩ pull up resistor is required Power ON Reset for Buck 1, Open drain output Low when Buck 1 output is 92% of target output. A 100 kΩ pull up resistor is required Power ON Reset for Buck 2, Open drain output Low when Buck 2 output is 92% of target output. A 100 kΩ pull up resistor is required Buck 1 Enable Buck 2 Enable Analog feedback ...

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