SNVSBU3 March   2021 LP87702

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 I2C Serial Bus Timing Parameters
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Descriptions
      1. 7.3.1  Step-Down DC/DC Converters
        1. 7.3.1.1 Overview
        2. 7.3.1.2 Transition Between PWM and PFM Modes
        3. 7.3.1.3 Buck Converter Load Current Measurement
      2. 7.3.2  Boost Converter
      3. 7.3.3  Spread-Spectrum Mode
      4. 7.3.4  Sync Clock Functionality
      5. 7.3.5  Power-Up
      6. 7.3.6  Buck and Boost Control
        1. 7.3.6.1 Enabling and Disabling Converters
        2. 7.3.6.2 Changing Buck Output Voltage
      7. 7.3.7  Enable and Disable Sequences
      8. 7.3.8  Window Watchdog
      9. 7.3.9  Device Reset Scenarios
      10. 7.3.10 Diagnostics and Protection Features
        1. 7.3.10.1 Voltage Monitorings
        2. 7.3.10.2 Interrupts
        3. 7.3.10.3 Power-Good Information to Interrupt, PG0, and PG1 Pins
          1. 7.3.10.3.1 PGx Pin Gated (Unusual) Mode
          2. 7.3.10.3.2 PGx Pin Operation in Continuous Mode
          3. 7.3.10.3.3 Summary of PG0, PG1 Gated, and Continuous Operating Modes
        4. 7.3.10.4 Warning Interrupts for System Level Diagnostics
          1. 7.3.10.4.1 Output Power Limit
          2. 7.3.10.4.2 Thermal Warning
        5. 7.3.10.5 Protections Causing Converter Disable
          1. 7.3.10.5.1 Short-Circuit and Overload Protection
          2. 7.3.10.5.2 Overvoltage Protection
          3. 7.3.10.5.3 Thermal Shutdown
        6. 7.3.10.6 Protections Causing Device Power Down
          1. 7.3.10.6.1 Undervoltage Lockout
      11. 7.3.11 OTP Error Correction
      12. 7.3.12 Operation of GPO Signals
      13. 7.3.13 Digital Signal Filtering
    4. 7.4 Device Functional Modes
      1. 7.4.1 Modes of Operation
    5. 7.5 Programming
      1. 7.5.1 I2C-Compatible Interface
        1. 7.5.1.1 Data Validity
        2. 7.5.1.2 Start and Stop Conditions
        3. 7.5.1.3 Transferring Data
        4. 7.5.1.4 I2C-Compatible Chip Address
        5. 7.5.1.5 Auto Increment Feature
    6. 7.6 Register Maps
      1. 7.6.1 Register Descriptions
        1. 7.6.1.1 LP8770_map Registers
  8. 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. 8.2.2.1 Application Components
          1. 8.2.2.1.1 Inductor Selection
          2. 8.2.2.1.2 Buck Input Capacitor Selection
          3. 8.2.2.1.3 Buck Output Capacitor Selection
          4. 8.2.2.1.4 Boost Input Capacitor Selection
          5. 8.2.2.1.5 Boost Output Capacitor Selection
          6. 8.2.2.1.6 Supply Filtering Components
      3. 8.2.3 Current Limit vs Maximum Output Current
      4. 8.2.4 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
7.3.10.3.1 PGx Pin Gated (Unusual) Mode

The PGx signal detects unexpected or unusual situations in this mode. Mode is selected by setting the PGx_MODE bit to 0 in the PG_CTRL register.

For the gated mode of operation, the PGx behaves as follows:

  • PGx is set to active or asserted state upon exiting the OTP configuration as an initial default state.
  • The PGx status is active or asserted during an 800-μs gated time period from the enable activation for each enabled rail, thereby gating-off the status indication.
  • The PGx state typically remains active or asserted for normal conditions during normal power-up sequencing and requested voltage changes.
  • The PGx status could change to inactive or de-asserted after an 800-μs gated time period if any output voltage is outside of regulation range during an abnormal power-up sequencing and requested voltage changes.
  • Using the gated mode of operation could allow the PGx signal to initiate an immediate power shutdown sequence if the PGx signal is wired-OR with signal connected to the EN input. This type of circuit configuration provides a smart PORz function for processor that eliminates the need for additional components to generate PORz upon start-up and to monitor voltage levels of key voltage domains.

PGx signal is set inactive if the output voltage of a monitored buck or boost converter is invalid or the output voltage is not valid at 800 µs from the enable of the converter, which should be considered when selecting the BUCKx_SLEW_RATE setting. Keep the sum of the soft start time and slew rate controlled part of the voltage ramp below 800 µs to avoid PGx triggering at start-up. In addition, the PGx is inactive when the invalid input voltage at VANA, VMON1, or VMON2 pin is detected.

Detected fault sets the corresponding fault bit in PG0_FAULT or in PG1_FAULT register. The detected fault must be cleared to continue the PGx monitoring. The over-voltage and thermal faults are cleared by writing 1 to the corresponding interrupt bits in INT_TOP_1 register. Converter, VMONx and VANA faults are cleared by writing 1 to the corresponding register bit in INT_BUCK, INT_BOOST, and INT_DIAG register, respectively. An example of the PGx pin operation in gated mode is shown in Figure 7-10 and the different use cases for the PGx signal operation are summarized in Table 7-6.

GUID-901DDA15-3AB3-4F0B-AA83-E627C6F46DA3-low.gifFigure 7-10 PGx Pin Operation in Gated Mode.