SNVSA37A October   2015  – May 2016 LM5175


  1. Features
  2. Applications
  3. Description
  4. Simplified Schematic
  5. Revision History
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Fixed Frequency Valley/Peak Current Mode Control with Slope Compensation
      2. 8.3.2  VCC Regulator and Optional BIAS Input
      3. 8.3.3  Enable/UVLO
      4. 8.3.4  Soft-Start
      5. 8.3.5  Overcurrent Protection
      6. 8.3.6  Average Input/Output Current Limiting
      7. 8.3.7  CCM/DCM Operation
      8. 8.3.8  Frequency and Synchronization (RT/SYNC)
      9. 8.3.9  Frequency Dithering
      10. 8.3.10 Output Overvoltage Protection (OVP)
      11. 8.3.11 Power Good (PGOOD)
      12. 8.3.12 Gm Error Amplifier
      13. 8.3.13 Integrated Gate Drivers
      14. 8.3.14 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown, Standby, and Operating Modes
      2. 8.4.2 MODE Pin Configuration
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1.  Custom Design with WEBENCH Tools
        2.  Frequency
        3.  VOUT
        4.  Inductor Selection
        5.  Output Capacitor
        6.  Input Capacitor
        7.  Sense Resistor (RSENSE)
        8.  Slope Compensation
        9.  UVLO
        10. Soft-Start Capacitor
        11. Dither Capacitor
        12. MOSFETs QH1 and QL1
        13. MOSFETs QH2 and QL2
        14. Frequency Compensation
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Custom Design with WEBENCH Tools
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Documentation Support
      1. 12.3.1 Related Documentation
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6 Pin Configuration and Functions

PWP Package
Top View
LM5175 po1_PWP_snvsa37.gif
RHF Package
Top View
LM5175 po2_RHF_snvsa37.gif

Pin Functions

EN/UVLO 1 26 Enable pin. For EN/UVLO < 0.4 V, the LM5175 is in a low current shutdown mode. For 0.7 V < EN/UVLO < 1.23 V, the controller operates in standby mode in which the VCC regulator is enabled but the PWM controller is not switching. For EN/UVLO > 1.23 V, the PWM function is enabled, provided VCC exceeds the VCC UV threshold.
VIN 2 27 The input supply pin to the IC. Connect VIN to a supply voltage between 3.5 V and 42 V.
VISNS 3 28 VIN sense input. Connect to the input capacitor.
MODE 4 1 Mode = GND, DCM, Hiccup Disabled (Set RMODE resistor to GND = 0 Ω)
Mode = 1.00 V, DCM, Hiccup Enabled (Set RMODE resistor to GND = 49.9 kΩ)
Mode = 1.85 V, CCM, Hiccup Enabled (Set RMODE resistor to GND = 93.1 kΩ)
Mode = VCC, CCM, Hiccup Disabled (Set RMODE resistor to VCC = 0 Ω)
DITH 5 2 A capacitor connected between the DITH pin and AGND is charged and discharged with a 10 uA current source. As the voltage on the DITH pin ramps up and down the oscillator frequency is modulated between –5% and +5% of the nominal frequency set by the RT resistor. Grounding the DITH pin will disable the dithering feature. In the external Sync mode, the DITH pin voltage is ignored.
RT/SYNC 6 3 Switching frequency programming pin. An external resistor is connected to the RT/SYNC pin and AGND to set the switching frequency. This pin can also be used to synchronize the PWM controller to an external clock.
SLOPE 7 4 A capacitor connected between the SLOPE pin and AGND provides the slope compensation ramp for stable current mode operation in both buck and boost mode.
SS 8 5 Soft-start programming pin. A capacitor between the SS pin and AGND pin programs soft-start time.
COMP 9 6 Output of the error amplifier. An external RC network connected between COMP and AGND compensates the regulator feedback loop.
AGND 10 7 Analog ground of the IC.
FB 11 8 Feedback pin for output voltage regulation. Connect a resistor divider network from the output of the converter to the FB pin.
VOSNS 12 9 VOUT sense input. Connect to the output capacitor.
Input or Output Current Sense Amplifier inputs. An optional current sense resistor connected between ISNS(+) and ISNS(–) can be located either on the input side or on the output side of the converter. If the sensed voltage across the ISNS(+) and ISNS(-) pins reaches 50 mV, a slow Constant Current (CC) control loop becomes active and starts discharging the soft-start capacitor to regulated the drop across ISNS(+) and ISNS(-) to 50 mV. Short ISNS(+) and ISNS(-) together to disable this feature.
CSG 15 12 The negative or ground input to the PWM current sense amplifier. Connect directly to the low-side (ground) of the current sense resistor.
CS 16 13 The positive input to the PWM current sense amplifier.
PGOOD 17 14 Power Good open drain output. PGOOD is pulled low when FB is outside a 0.8 V ±10% regulation window.
The boost and the buck side switching nodes respectively.
Output of the high-side gate drivers. Connect directly to the gates of the high-side MOSFETs.
An external capacitor is required between the BOOT1, BOOT2 pins and the SW1, SW2 pins respectively to provide bias to the high-side MOSFET gate drivers.
Output of the low-side gate drivers. Connect directly to the gates of the low-side MOSFETs.
PGND 22 19 Power ground of the IC. The high current ground connection to the low-side gate drivers.
VCC 23 20 Output of the VCC bias regulator. Connect capacitor to ground.
BIAS 24 21 Optional input to the VCC bias regulator. Powering VCC from an external supply instead of VIN can reduce power loss at high VIN. For VBIAS > 8 V, the VCC regulator draws power from the BIAS pin. The BIAS pin voltage must not exceed 40 V.
PowerPAD™ - - The PowerPAD should be soldered to the analog ground. If possible, use thermal vias to connect to a PCB ground plane for improved power dissipation.