SLVSHH4 July   2024 TPS546E25

ADVANCE INFORMATION  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
  7. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  D-CAP4 Control
        1. 6.3.1.1 Loop Compensation
      2. 6.3.2  Internal VCC LDO and Using an External Bias on VCC Pin and VDRV Pin
      3. 6.3.3  Input Undervoltage Lockout (UVLO)
        1. 6.3.3.1 Fixed VCC_OK UVLO
        2. 6.3.3.2 Fixed VDRV UVLO
        3. 6.3.3.3 Programmable PVIN UVLO
        4. 6.3.3.4 Control (CNTL)Enable
      4. 6.3.4  Differential Remote Sense and Internal, External Feedback Divider
      5. 6.3.5  Set the Output Voltage and VORST#
      6. 6.3.6  Start-Up and Shutdown
      7. 6.3.7  Dynamic Voltage Slew Rate
      8. 6.3.8  Set Switching Frequency
      9. 6.3.9  Switching Node (SW)
      10. 6.3.10 Overcurrent Limit and Low-side Current Sense
      11. 6.3.11 Negative Overcurrent Limit
      12. 6.3.12 Zero-Crossing Detection
      13. 6.3.13 Input Overvoltage Protection
      14. 6.3.14 Output Overvoltage and Undervoltage Protection
      15. 6.3.15 Overtemperature Protection
      16. 6.3.16 Telemetry
    4. 6.4 Device Functional Modes
      1. 6.4.1 Forced Continuous-Conduction Mode
      2. 6.4.2 DCM Light Load Operation
      3. 6.4.3 Powering the Device From a 12V Bus
      4. 6.4.4 Powering the Device From a Split-rail Configuration
      5. 6.4.5 Pin Strapping
        1. 6.4.5.1 Programming MSEL1
        2. 6.4.5.2 Programming PMB_ADDR
        3. 6.4.5.3 Programming MSEL2
        4. 6.4.5.4 Programming VSEL\FB
    5. 6.5 Programming
      1. 6.5.1 Supported PMBus Commands
  8. Register Maps
    1. 7.1  Conventions for Documenting Block Commands
    2. 7.2  (01h) OPERATION
    3. 7.3  (02h) ON_OFF_CONFIG
    4. 7.4  (03h) CLEAR_FAULTS
    5. 7.5  (04h) PHASE
    6. 7.6  (09h) P2_PLUS_WRITE
    7. 7.7  (0Ah) P2_PLUS_READ
    8. 7.8  (0Eh) PASSKEY
    9. 7.9  (10h) WRITE_PROTECT
    10. 7.10 (15h) STORE_USER_ALL
    11. 7.11 (16h) RESTORE_USER_ALL
    12. 7.12 (19h) CAPABILITY
    13. 7.13 (1Bh) SMBALERT_MASK
    14. 7.14 (20h) VOUT_MODE
    15. 7.15 (21h) VOUT_COMMAND
    16. 7.16 (22h) VOUT_TRIM
    17. 7.17 (24h) VOUT_MAX
    18. 7.18 (25h) VOUT_MARGIN_HIGH
    19. 7.19 (26h) VOUT_MARGIN_LOW
    20. 7.20 (27h) VOUT_TRANSITION_RATE
    21. 7.21 (29h) VOUT_SCALE_LOOP
    22. 7.22 (2Ah) VOUT_SCALE_MONITOR
    23. 7.23 (2Bh) VOUT_MIN
    24. 7.24 (33h) FREQUENCY_SWITCH
    25. 7.25 (35h) VIN_ON
    26. 7.26 (36h) VIN_OFF
    27. 7.27 (39h) IOUT_CAL_OFFSET
    28. 7.28 (40h) VOUT_OV_FAULT_LIMIT
    29. 7.29 (41h) VOUT_OV_FAULT_RESPONSE
    30. 7.30 (42h) VOUT_OV_WARN_LIMIT
    31. 7.31 (43h) VOUT_UV_WARN_LIMIT
    32. 7.32 (44h) VOUT_UV_FAULT_LIMIT
    33. 7.33 (45h) VOUT_UV_FAULT_RESPONSE
    34. 7.34 (46h) IOUT_OC_FAULT_LIMIT
    35. 7.35 (48h) IOUT_OC_LV_FAULT_LIMIT
    36. 7.36 (49h) IOUT_OC_LV_FAULT_RESPONSE
    37. 7.37 (4Ah) IOUT_OC_WARN_LIMIT
    38. 7.38 (4Fh) OT_FAULT_LIMIT
    39. 7.39 (50h) OT_FAULT_RESPONSE
    40. 7.40 (51h) OT_WARN_LIMIT
    41. 7.41 (55h) VIN_OV_FAULT_LIMIT
    42. 7.42 (60h) TON_DELAY
    43. 7.43 (61h) TON_RISE
    44. 7.44 (64h) TOFF_DELAY
    45. 7.45 (65h) TOFF_FALL
    46. 7.46 (78h) STATUS_BYTE
    47. 7.47 (79h) STATUS_WORD
    48. 7.48 (7Ah) STATUS_VOUT
    49. 7.49 (7Bh) STATUS_IOUT
    50. 7.50 (7Ch) STATUS_INPUT
    51. 7.51 (7Dh) STATUS_TEMPERATURE
    52. 7.52 (7Eh) STATUS_CML
    53. 7.53 (7Fh) STATUS_OTHER
    54. 7.54 (80h) STATUS_MFR_SPECIFIC
    55. 7.55 (88h) READ_VIN
    56. 7.56 (8Bh) READ_VOUT
    57. 7.57 (8Ch) READ_IOUT
    58. 7.58 (8Dh) READ_TEMPERATURE_1
    59. 7.59 (98h) PMBUS_REVISION
    60. 7.60 (99h) MFR_ID
    61. 7.61 (9Ah) MFR_MODEL
    62. 7.62 (9Bh) MFR_REVISION
    63. 7.63 (ADh) IC_DEVICE_ID
    64. 7.64 (AEh) IC_DEVICE_REV
    65. 7.65 (D1h) SYS_CFG_USER1
    66. 7.66 (D2h) PMBUS_ADDR
    67. 7.67 (D4h) COMP
    68. 7.68 (D5h) VBOOT_OFFSET_1
    69. 7.69 (D6h) STACK_CONFIG
    70. 7.70 (D8h) PIN_DETECT_OVERRIDE
    71. 7.71 (D9h) NVM_CHECKSUM
    72. 7.72 (DAh) READ_TELEMETRY
    73. 7.73 (79h) STATUS_ALL
    74. 7.74 (DDh) EXT_WRITE_PROTECTION
    75. 7.75 (A4h) IMON_CAL
    76. 7.76 (FCh) FUSION_ID0
    77. 7.77 (FDh) FUSION_ID1
  9. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Application
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Input Capacitor Selection
        2. 8.2.3.2 Inductor Selection
        3. 8.2.3.3 Output Capacitor Selection
        4. 8.2.3.4 Compensation Selection
        5. 8.2.3.5 VCC and VRDV Bypass Capacitors
        6. 8.2.3.6 BOOT Capacitor Selection
        7. 8.2.3.7 VOSNS and GOSNS Capacitor Selection
        8. 8.2.3.8 PMBus Address Resistor Selection
      4. 8.2.4 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
        1. 8.4.2.1 Thermal Performance on TPS546E25EVM
  10. Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

Package Options

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

Overcurrent Limit and Low-side Current Sense

For a synchronous buck converter, the inductor current increases at a linear rate determined by the input voltage, the output voltage, and the output inductor value during the high-side MOSFET on-time (ON time). During the low-side MOSFET on-time (OFF time), this inductor current decreases linearly per slew rate determined by the output voltage and the output inductor value. The inductor during the OFF time, even with a negative slew rate, usually flows from the device SW node to the load the device which is said to be sourcing current and the output current is declared to be positive. This section describes the overcurrent limit feature based on the positive low-side current. The next section describes the overcurrent limit feature based on the negative low-side current.

The positive overcurrent limit (OCL) feature in the TPS546E25 device is implemented to clamp low-side valley current on a cycle-by-cycle basis. The inductor current is monitored during the OFF time by sensing the current flowing through the low-side MOSFET. When the sensed low-side MOSFET current remains above the selected OCL threshold, the low-side MOSFET stays ON until the sensed current level becomes lower than the selected OCL threshold. This operation extends the OFF time and pushes the next ON time (where the high-side MOSFET turns on) out. As a result, the OCL bit in STATUS_IOUT is set, also the average output current sourced by the device is reduced. As long as the load pulls a heavy load where the sensed low-side valley current exceeds the selected OCL threshold, the device continuously operates in this clamping mode which extends the current OFF time and pushes the next ON time out. The device does not implement a fault response circuit directly tied to the overcurrent limit circuit, instead, the VOUT Tracking UVF function is used to shuts the device down under an overcurrent fault. During an overcurrent event, the current sunk by the load (IOUT) exceeds the current sourced by the device to the output capacitors, thus, the output voltage tends to decrease. Eventually, when the output voltage falls below the selected undervoltage fault threshold, the VOUT Tracking UVF comparator detects and shuts down the device after the UVF Response Delay (programmable in VOUT_UV_FAULT_RESPONSE register). The device then responds to the Tracking UVF trigger per bit[3] RESTART selection in VOUT_UV_FAULT_RESPONSE register. With the RESTART bit unset (value "0"), the device latches OFF both high-side and low-side drivers. The latch is cleared with a reset of VCC or by toggling the EN pin. With the RESTART bit set (value "1"), the device enters hiccup mode and re-starts automatically after a hiccup sleep time of 56ms, without limitation on the number of restart attempts. In other words, the response to an overcurrent fault is set by the programmed UVF response.

If an OCL condition happens during a soft-start ramp the device still operates with the cycle-by-cycle current limit based on the sensed low-side valley current. This operation can limit the energy charged into the output capacitors thus the output voltage likely ramps up slower than the desired soft-start slew rate. During the soft start, the VOUT Tracking UVF comparator is disabled thus the device does not respond to a UVF event. Upon the completion of the soft start, the VOUT Tracking UVF comparator is enabled, then the device starts responding to the UVF event.

The OCL feature in the device is implemented by detecting the low-side valley current through analog circuitries and has no relationship with the integrated Analog-to-Digital converter (ADC). The telemetry analog-front-end gets an input from the low-side current sense circuit and average low-side MOSFET current from the start to the end of each low-side MOSFET on time. By this method, the telemetry sub-system reports the load current (IOUT) which is the average value of the inductor current but not peak or valley values.