SNVAA98 January   2024 LM25148 , LM74910-Q1 , TPS38700 , TPS389006 , TPS389006-Q1 , TPS628301 , TPS628302 , TPS628303 , TPS6287B10 , TPS6287B15 , TPS6287B20 , TPS6287B25 , TPS746

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. Introduction
  5. Design Parameters
  6. Schematics
  7. Design Considerations
  8. Front-End Protection
  9. 3.3V Always-ON Bias Supply
  10. 5V Pre-Regulator Buck Converter
  11. Low-Voltage High-Current Core Rail Buck Converter
  12. On-Board Core Rail Output Load Transient Stepper
  13. 10Multiple Peripheral Rail Buck Converters Sub-Circuits Schematic
  14. 11Voltage Supervisor and Sequencer
  15. 1212-Channel Sequencer Alternative
  16. 13Summary
  17. 14References

Low-Voltage High-Current Core Rail Buck Converter

For the low-voltage core rail, a 2-phase interleaved synchronous Buck converter is implemented using two of the TPS6287B25 regulator IC. This device can be used as a single-phase converter, or can be daisy-chained with other TPS6287B25 ICs to work together as an interleaved system. For the VE2302 device, a 2-phase TPS6287B25 design is implemented, with each phase switching at 1.5MHz. Phase 2 can be programmed to have a 180-degree phase shift from Phase 1, leading to an interleaved design, with an effective switching frequency of 3MHz. The TPS6287B25 has I2C capability, which can be used to program various features, functions, and parameters (see device data sheet for details). When configured as a multi-phase converter, the first phase device in the chain of devices becomes the main controller. This is the device that I2C communication is made with, as well as sets and dictates to the other phases, the output voltage setpoint, the compensation voltage, and main synchronization clock. To be able to provide significant amount of current in a very short time window, features like droop compensation implemented in TPS6287B25, selectable through I2C, helps to reduce overshoot and undershoot of the core voltage during steep load variations. Table 8-1 shows the IC pin functions for the primary/control phase device and the non-primary phase devices.

Alternative inductor options include: SLC1480-111MLB, SLR7010-101KED, SLC1049-101MLB

Table 8-1 TPS6287B25 Primary Phase and Non-Primary Phase Pin Functions
Pin NamePrimary Phase/Device FunctionNon-Primary Phase/Device Function
VINInput voltage; connect to VinInput voltage; connect to Vin
ENEnable pin; gang all phase EN pins together
MODE/SYNCSets the operating mode for all phasesSwitching clock input received from preceding phase
SYNC_OUTSwitching clock output to drive next phaseSwitching clock output to drive next phase unless no other phases to drive
VSET1Configures and sets default output voltageNo function; GND this pin
VSET2Configures and sets default output voltageNo function; GND this pin
SCLI2C clockNo function; GND this pin
SDAI2C dataNo function; GND this pin
SWSwitch node; connect to power inductor
VOSNSOutput rail positive node remote senseOutput rail positive node remote sense; connect to positive of local output capacitor
GOSNSOutput rail GND node remote senseOutput rail GND node remote sense; connect to GND of local output capacitor
COMPCompensation network pin; gang all COMP pins together
PGPower good output; gang all PG pins together
AGNDAnalog ground; perform proper connection as shown in data sheet or evaluation board
GNDPower ground; perform proper connection as shown in data sheet or evaluation board
EPExposed pad; connect to power ground and flood GND polygon pour to dissipate heat; see data sheet or evaluation board for details