SNVSAL1C December   2017  – June 2021 LP87702-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 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 I2C Serial Bus Timing Parameters
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Descriptions
      1. 8.3.1  Step-Down DC/DC Converters
        1. 8.3.1.1 Overview
        2. 8.3.1.2 Transition Between PWM and PFM Modes
        3. 8.3.1.3 Buck Converter Load Current Measurement
      2. 8.3.2  Boost Converter
      3. 8.3.3  Spread-Spectrum Mode
      4. 8.3.4  Sync Clock Functionality
      5. 8.3.5  Power-Up
      6. 8.3.6  Buck and Boost Control
        1. 8.3.6.1 Enabling and Disabling Converters
        2. 8.3.6.2 Changing Buck Output Voltage
      7. 8.3.7  Enable and Disable Sequences
      8. 8.3.8  Window Watchdog
      9. 8.3.9  Device Reset Scenarios
      10. 8.3.10 Diagnostics and Protection Features
        1. 8.3.10.1 Voltage Monitorings
        2. 8.3.10.2 Interrupts
        3. 8.3.10.3 Power-Good Information to Interrupt, PG0, and PG1 Pins
          1. 8.3.10.3.1 PGx Pin Gated (Unusual) Mode
          2. 8.3.10.3.2 PGx Pin Operation in Continuous Mode
          3. 8.3.10.3.3 Summary of PG0, PG1 Gated, and Continuous Operating Modes
        4. 8.3.10.4 Warning Interrupts for System Level Diagnostics
          1. 8.3.10.4.1 Output Power Limit
          2. 8.3.10.4.2 Thermal Warning
        5. 8.3.10.5 Protections Causing Converter Disable
          1. 8.3.10.5.1 Short-Circuit and Overload Protection
          2. 8.3.10.5.2 Overvoltage Protection
          3. 8.3.10.5.3 Thermal Shutdown
        6. 8.3.10.6 Protections Causing Device Power Down
          1. 8.3.10.6.1 Undervoltage Lockout
      11. 8.3.11 OTP Error Correction
      12. 8.3.12 Operation of GPO Signals
      13. 8.3.13 Digital Signal Filtering
    4. 8.4 Device Functional Modes
      1. 8.4.1 Modes of Operation
    5. 8.5 Programming
      1. 8.5.1 I2C-Compatible Interface
        1. 8.5.1.1 Data Validity
        2. 8.5.1.2 Start and Stop Conditions
        3. 8.5.1.3 Transferring Data
        4. 8.5.1.4 I2C-Compatible Chip Address
        5. 8.5.1.5 Auto Increment Feature
    6. 8.6 Register Maps
      1. 8.6.1 Register Descriptions
        1. 8.6.1.1 LP8770_map Registers
  9. 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. 9.2.2.1 Application Components
          1. 9.2.2.1.1 Inductor Selection
          2. 9.2.2.1.2 Buck Input Capacitor Selection
          3. 9.2.2.1.3 Buck Output Capacitor Selection
          4. 9.2.2.1.4 Boost Input Capacitor Selection
          5. 9.2.2.1.5 Boost Output Capacitor Selection
          6. 9.2.2.1.6 Supply Filtering Components
      3. 9.2.3 Current Limit vs Maximum Output Current
      4. 9.2.4 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 Third-Party Products Disclaimer
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Section 9.2 shows the inductors L0, L1, and L2. The inductor's inductance and DCR affects the buck and boost converter's control loop. Table 9-2 lists the recommended inductors, or similar ones, that should be used. Pay attention to the inductor's saturation current and temperature rise current. Check that the saturation current is higher than the peak current limit and the temperature rise current is higher than the maximum expected rms output current. Section 7 shows the minimum effective inductance that ensures good performance. The inductor's DC resistance should be less than 0.05 Ω for good efficiency at high-current condition. The inductor AC loss (resistance) also affects conversion efficiency. Higher Q factor at switching frequency usually gives better efficiency at light load to middle load. Shielded inductors are preferred as they radiate less noise.

Table 9-2 Recommended Inductors for Buck Converters
MANUFACTURER PART NUMBER VALUE DIMENSIONS
L × W x× H (mm)		 RATED DC CURRENT,
ISAT max / ITEMP max (A)		 DCR typ / max (mΩ)
MURATA DFE252012PD-R47M 0.47 µH (20%) 2.5 × 2 × 1.2 5.2 / 4.0(1) - / 27
TDK TFM252012ALMAR47MTAA 0.47 µH (20%) 2.5 × 2 × 1.2 5.8 / 4.9(1) 19 / 24
(1) Operating temperature range is up to 125°C including self temperature rise.
Table 9-3 Recommended Inductor for Boost Converters
MANUFACTURER PART NUMBER VALUE DIMENSIONS
L × W x× H (mm)		 RATED DC CURRENT,
ISAT max / ITEMP max (A)		 DCR typ / max (mΩ)
MURATA DFE252012PD-1R0M 1 µH (20%) 2.5 × 2 × 1.2 3.8 / 3.2 (1) - / 42
TDK TFM25201ALMA1R0MTAA 1 µH (20%) 2.5 × 2 × 1.2 4.2 / 3.7 (1) 35 / 42