SLVSFJ3C May   2022  – October 2023 TPS62870-Q1 , TPS62871-Q1 , TPS62872-Q1 , TPS62873-Q1

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Revision History
  6. Description (continued)
  7. Device Options
  8. Pin Configuration and Functions
  9. Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 I2C Interface Timing Characteristics
    7. 8.7 Timing Requirements
    8. 8.8 Typical Characteristics
  10. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Fixed-Frequency DCS Control Topology
      2. 9.3.2  Forced PWM and Power Save Modes
      3. 9.3.3  Precise Enable
      4. 9.3.4  Start-Up
      5. 9.3.5  Switching Frequency Selection
      6. 9.3.6  Output Voltage Setting
        1. 9.3.6.1 Output Voltage Range
        2. 9.3.6.2 Output Voltage Setpoint
        3. 9.3.6.3 Non-Default Output Voltage Setpoint
        4. 9.3.6.4 Dynamic Voltage Scaling
      7. 9.3.7  Compensation (COMP)
      8. 9.3.8  Mode Selection and Clock Synchronization (MODE/SYNC)
      9. 9.3.9  Spread Spectrum Clocking (SSC)
      10. 9.3.10 Output Discharge
      11. 9.3.11 Undervoltage Lockout (UVLO)
      12. 9.3.12 Overvoltage Lockout (OVLO)
      13. 9.3.13 Overcurrent Protection
        1. 9.3.13.1 Cycle-by-Cycle Current Limiting
        2. 9.3.13.2 Hiccup Mode
        3. 9.3.13.3 Current Limit Mode
      14. 9.3.14 Power Good (PG)
        1. 9.3.14.1 Standalone or Primary Device Behavior
        2. 9.3.14.2 Secondary Device Behavior
      15. 9.3.15 Remote Sense
      16. 9.3.16 Thermal Warning and Shutdown
      17. 9.3.17 Stacked Operation
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-On Reset
      2. 9.4.2 Undervoltage Lockout
      3. 9.4.3 Standby
      4. 9.4.4 On
    5. 9.5 Programming
      1. 9.5.1 Serial Interface Description
      2. 9.5.2 Standard, Fast, Fast Mode Plus Protocol
      3. 9.5.3 I2C Update Sequence
      4. 9.5.4 I2C Register Reset
    6. 9.6 Register Map
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Selecting the Inductor
        2. 10.2.2.2 Selecting the Input Capacitors
        3. 10.2.2.3 Selecting the Compensation Resistor
        4. 10.2.2.4 Selecting the Output Capacitors
        5. 10.2.2.5 Selecting the Compensation Capacitor, CC
        6. 10.2.2.6 Selecting the Compensation Capacitor, CC2
      3. 10.2.3 Application Curves
    3. 10.3 Best Design Practices
    4. 10.4 Power Supply Recommendations
    5. 10.5 Layout
      1. 10.5.1 Layout Guidelines
      2. 10.5.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    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
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Stacked Operation

The user can connect multiple devices in parallel in what is known as a "stack"; for example, to increase output current capability or reduce device junction temperature. A stack comprises one primary device and one or more secondary devices. During initialization, each device monitors its SYNC_OUT pin to determine if must operate as a primary device or a secondary device:

  • If there is a 47-kΩ resistor between the SYNC_OUT pin and ground, the device operates as a secondary device.
  • If the SYNC_OUT pin is high impedance, the device operates as a primary device.

Figure 9-14 shows the recommended interconnections in a stack of two TPS6287x-Q1 devices.


GUID-E4C3AB1E-6307-434D-ACE3-86CBAF44702C-low.svg

Figure 9-14 Two TPS6287x-Q1 Devices in a Stacked Configuration

The key points to note are:

  • All the devices in the stack share a common enable signal, which must be pulled up with a resistance of at least 15 kΩ.
  • All the devices in the stack share a common power-good signal.
  • All the devices in the stack share a common compensation signal.
  • All secondary devices must connect a 47-kΩ resistor between the SYNC_OUT pin and ground.

  • The remote sense pins (VOSNS and GOSNS) of each device must be connected (do not leave these pins floating).
  • Each device must be configured for the same switching frequency.
  • The primary device must be configured for forced PWM operation (secondary devices are automatically configured for forced PWM operation).
  • A stacked configuration can support synchronization to an external clock or spread-spectrum clocking.
  • Only the VSEL pin of the primary device is used to set the default output voltage. The VSEL pin of secondary devices is not used and must be connected to ground.
  • The SDA and SCL pins of secondary devices are not used and must be connected to ground.
  • A stacked configuration uses a daisy-chained clocking signal, in which each device switches with a phase offset of approximately 140° relative to the adjacent devices in the daisy-chain. To daisy-chain the clocking signal, connect the SYNC_OUT pin of the primary device to the MODE/SYNC pin of the first secondary device. Connect the SYNC_OUT pin of the first secondary device to the MODE/SYNC pin of the second secondary device. Continue this connection scheme for all devices in the stack, to daisy-chain them together.
  • Hiccup overcurrent protection must not be used in a stacked configuration.

In a stacked configuration, the common enable signal also acts as a SYSTEM_READY signal (see Section 9.3.3). Each device in the stack can pull its EN pin low during device start-up or when a fault occurs. Thus, the stack is only enabled when all devices have completed their start-up sequence and are fault-free. A fault in any one device disables the whole stack for as long as the fault condition exists.

During start-up, the primary converter pulls the COMP pin low for as long as the enable signal (SYSTEM_READY) is low. When the enable signal goes high, the primary device actively controls the COMP pin and all converters in the stack follow the COMP voltage. During start-up, each device in the stack pulls its PG pin low while it initializes. When initialization is complete, each secondary device in the stack sets its PG pin to a high impedance and the primary device alone controls the state of the PG signal. The PG pin goes high when the stack has completed its start-up ramp and the output voltage is within specification. The secondary converters in the stack detect the rising edge of the power-good signal and switch from DCM operation to CCM operation. After the stack has successfully started up, the primary device controls the power-good signal in the normal way. In a stacked configuration, there are some faults that only affect individual devices, and other faults that affect all devices. For example, if one device enters current limit, only that device is affected. But a thermal shutdown or undervoltage lockout event in one device disables all devices through the shared enable (SYSTEM_READY) signal.

Functionality During Stacked Operation

Some device features are not available during stacked operation, or are only available in the primary converter. Table 9-8 summarizes the available functionality during stacked operation.

Table 9-8 Functionality During Stacked Operation
FunctionPrimary DeviceSecondary DeviceRemark
UVLOYesYesCommon enable signal
OVLOYesYesCommon enable signal
OCP – Current LimitYesYesIndividual
OCP – Hiccup OCPNoNoDo not use during stacked operation.
Thermal ShutdownYesYesCommon enable signal
Power-Good (Window Comparator)YesNoPrimary device only
I2C InterfaceYesNoPrimary device only
DVSThrough I2CNoVoltage loop controlled by primary device only
SSCThrough I2CNoDaisy-chained from primary device to secondary devices
SYNCYesYesSynchronization clock applied to primary device
Precise EnableNoNoOnly binary enable
Output DischargeYesYesAlways enabled in secondary devices

Fault Handling During Stacked Operation

In a stacked configuration, there are some faults that only affect individual devices and other faults that affect all devices. For example, if one device enters current limit, only that device is affected. A thermal shutdown or undervoltage lockout event in one device disables all devices through the shared enable (SYSTEM_READY) signal. Table 9-9 summarizes the fault handling of the TPS6287x-Q1 devices during stacked operation.

Table 9-9 Fault Handling During Stacked Operation
Fault ConditionDevice ResponseSystem Response
UVLOEnable signal pulled lowNew soft start
OVLO
Thermal shutdown
Current limitEnable signal remains highError amplifier clamped