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LM3678 Dataheets PDF



Part Number LM3678
Manufacturers Texas Instruments
Logo Texas Instruments
Description High-Performance Miniature 1.5-A Step-Down DC-DC Converter
Datasheet LM3678 DatasheetLM3678 Datasheet (PDF)

LM3678 www.ti.com SNVS464C – APRIL 2008 – REVISED MAY 2013 High-Performance Miniature 1.5-A Step-Down DC-DC Converter for Handheld Applications Check for Samples: LM3678 FEATURES 1 •2 VOUT = 0.8 V or 1.2 V • VIN = 2.5 V to 5.5 V • 1.5-A Maximum Load Capability • 3.3-MHz (Typical) PWM Fixed Switching Frequency Allows Use of 1-µH Inductor • ±3% DC Output Voltage Precision • 0.01-µA (Typical) Shutdown Current • Internal Synchronous Rectification for High Efficiency • Internal Soft Start • Curre.

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LM3678 www.ti.com SNVS464C – APRIL 2008 – REVISED MAY 2013 High-Performance Miniature 1.5-A Step-Down DC-DC Converter for Handheld Applications Check for Samples: LM3678 FEATURES 1 •2 VOUT = 0.8 V or 1.2 V • VIN = 2.5 V to 5.5 V • 1.5-A Maximum Load Capability • 3.3-MHz (Typical) PWM Fixed Switching Frequency Allows Use of 1-µH Inductor • ±3% DC Output Voltage Precision • 0.01-µA (Typical) Shutdown Current • Internal Synchronous Rectification for High Efficiency • Internal Soft Start • Current Overload and Thermal Shutdown Protection APPLICATIONS • PDAs and Smart Phones • Personal Media Players • W-LAN • USB Modem Applications • Digital Still Cameras • Portable Hard Disk Drives DESCRIPTION The LM3678 step-down DC-DC converter is optimized for powering low-voltage circuits from a single Li-Ion cell battery and input voltage rails from 2.5 V to 5.5 V. It provides up to 1.5-A load current, over the entire input voltage range. LM3678 offers a 0.8V or 1.2V option. One of the pair of voltages is set through the VSELECT pin. LM3678 operates in PWM mode with a fixed frequency of 3.3 MHz. Internal synchronous rectification provides high efficiency during PWM mode operation. In shutdown mode, the device turns off and reduces battery consumption to 0.01 µA (typical). The LM3678 is available in a 3mm x 3mm DSC-10 package. A high switching frequency of 3.3 MHz (typical) allows use of tiny surface-mount components. Only three external surface-mount components, an inductor and two ceramic capacitors, are required (solution size less than 33 mm2). For voltages other than the voltage shown, contact TI or your distributor. VIN = 2.5V to 5.5V CIN 10 PF Typical Application Circuit VDD VDD 1 PH SW FB COUT EN PWM LM3678 0.8V/1.2V VSELECT GND PGOOD GND VOUT 22 PF NOTE: VSEL H = 1.2V, VSEL L = 0.8V EFFICIENCY (%) Efficiency vs. Output Current ( VOUT = 1.2V) VIN = 2.5V, 2.7V 90 80 70 60 VIN = 3.6V 50 40 30 VIN = 4.5V 20 10 0 VIN = 5.5V Figure 1. 0.010 0.100 1.000 LOAD (A) Figure 2. 10.000 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. 2 PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2008–2013, Texas Instruments Incorporated LM3678 SNVS464C – APRIL 2008 – REVISED MAY 2013 Functional Block Diagram EN VIN www.ti.com SW Undervoltage Lockout Ramp Generator Soft Start Thermal Shutdown Bandgap 2 MHz Oscillator Current Limit Comparator + - Ref1 PFM Current Comparator + - Ref2 + Error Amp PWM Comparator Control Logic Driver VREF + 0.5V - VCOMP + 1.0V - Frequency Compensation + - Zero Crossing Comparator Fixed Ver FB VSELECT PGOOD PWM Figure 3. LM3678 Block Diagram GND 2 Submit Documentation Feedback Product Folder Links: LM3678 Copyright © 2008–2013, Texas Instruments Incorporated www.ti.com Connection Diagram and Package Mark Information LM3678 SNVS464C – APRIL 2008 – REVISED MAY 2013 GND GND SW VDD VDD 1 2 3 4 5 10 FB D 9 EN A 8 PWM P 7 PGOOD 6 VSELECT FB 10 EN 9 PWM PGOOD VSELECT 8 7 6 D A P 1 GND 2 GND 3 SW 4 VDD 5 VDD Figure 4. Top View Figure 5. Bottom View Pin No. 1 2 3 4 5 6 7 8 9 10 DAP Name GND GND SW VDD VDD VSELECT PGOOD PWM EN FB DAP Table 1. Pin Descriptions Description Power Ground pin. Analog Ground Pin Switching node connection to the internal PFET switch and NFET synchronous rectifier Analog supply input. Connect to the input filter capacitor (see Figure 1). Power supply Input. Connect to the input filter capacitor (see Figure 1). Output voltage select (For example) VSELECT = LOW, VOUT = 0.8V VSELECT = HIGH , VOUT = 1.2V Power Good Flag. This common drain logic output is pulled to ground when the output voltage is not within ±7.5% of regulation. Connect PWM pin to VIN. Enable pin. The device is in shutdown mode when voltage to this pin is <0.4V and enabled when >1.0V. Do not leave this pin floating. Feedback analog input. Connect directly to the output filter capacitor for fixed voltage versions. Die Attach Pad, connect the DAP to GND on PCB layout to enhance thermal performance. It should not be used as a primary ground connection. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings(1) VIN Pin: Voltage to GND EN Pin FB, SW Pin Continuous Power Dissipation(2) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Soldering, 10 seconds) −0.2V to 6.0V −0.2.


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