SNVSB97A December   2018  – September 2021 LM34936-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Fixed Frequency Valley/Peak Current Mode Control with Slope Compensation
      2. 7.3.2  VCC Regulator and Optional BIAS Input
      3. 7.3.3  Enable/UVLO
      4. 7.3.4  Soft Start
      5. 7.3.5  Overcurrent Protection
      6. 7.3.6  Average Input/Output Current Limiting
      7. 7.3.7  Operation Above 28-V Input
      8. 7.3.8  CCM Operation
      9. 7.3.9  Frequency and Synchronization (RT/SYNC)
      10. 7.3.10 Frequency Dithering
      11. 7.3.11 Output Overvoltage Protection (OVP)
      12. 7.3.12 Power Good (PGOOD)
      13. 7.3.13 Gm Error Amplifier
      14. 7.3.14 Integrated Gate Drivers
      15. 7.3.15 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown, Standby, and Operating Modes
      2. 7.4.2 MODE Pin Configuration
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 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. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. Custom Design with WEBENCH Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Pin Configuration and Functions

GUID-D338307D-402D-402B-B340-9D0D494A666E-low.gif Figure 5-1 28-Pin HTSSOP With PowerPADPWP Package(Top View)
Table 5-1 Pin Functions
EN/UVLO 1 Enable pin. For EN/UVLO < 0.4 V, the LM34936-Q1 is in a low current shutdown mode. For EN/UVLO > 1.22 V, the PWM function is enabled, provided VCC exceeds the VCC UV threshold.
VIN 2 The input supply pin to the IC. Connect VIN to a supply voltage between 4.2 V and 30 V.
VISNS 3 VIN sense input. Connect to power stage input rail.
MODE 4 1.38 V < MODE < 2.22 V : CCM, Hiccup Enabled (Set RMODE resistor to AGND = 93.1 kΩ)
2.6 V < MODE < VCC: CCM, Hiccup Disabled (Set RMODE resistor to AGND = 200 kΩ or connect to VCC)
DITH 5 A capacitor connected between the DITH pin and AGND is charged and discharged with a current source. As the voltage on the DITH pin ramps up and down, the oscillator frequency is modulated by 10% of the nominal frequency set by the RT resistor. Grounding the DITH pin will disable the dithering feature. In external Sync mode, the DITH pin voltage is ignored.
RT/SYNC 6 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 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 Soft-start programming pin. A capacitor between the SS pin and AGND pin programs soft-start time.
COMP 9 Output of the error amplifier. An external RC network connected between COMP and AGND compensates the regulator feedback loop.
AGND 10 Analog ground of the IC
FB 11 Feedback pin for output voltage regulation. Connect a resistor divider network from the output of the converter to the FB pin.
VOSNS 12 VOUT sense input. Connect to the power stage output rail.
ISNS(–) 13 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 regulate the drop across ISNS(+) and ISNS(–) to 50 mV. Short ISNS(+) and ISNS(–) together to disable this feature.
ISNS(+) 14
CSG 15 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 The positive input to the PWM current sense amplifier
PGOOD 17 Power-Good open-drain output. PGOOD is pulled low when FB is outside a –9%/+10% regulation window around 0.8-V VREF.
SW2 18 The boost and the buck side switching nodes, respectively
SW1 28
HDRV2 19 Output of the high-side gate drivers. Connect directly to the gates of the high-side MOSFETs.
HDRV1 27
BOOT2 20 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.
BOOT1 26
LDRV2 21 Output of the low-side gate drivers. Connect directly to the gates of the low-side MOSFETs.
LDRV1 25
PGND 22 Power ground of the IC. The high current ground connection to the low-side gate drivers
VCC 23 Output of the VCC bias regulator. Connect the capacitor to ground.
BIAS 24 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.
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.