SLVS753C February   2007  – November 2016 TPS40180

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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Current Sensing and Overcurrent Detection
      2. 7.3.2 Hiccup Fault Recovery
      3. 7.3.3 Selecting Current Sense Network Components
      4. 7.3.4 PGOOD Functionality
      5. 7.3.5 Output Overvoltage and Undervoltage Protection
      6. 7.3.6 Overtemperature Protection
      7. 7.3.7 eTRIM™
      8. 7.3.8 Connections Between Controllers for Stacking
      9. 7.3.9 VSH Line in the Multiphase
    4. 7.4 Device Functional Modes
      1. 7.4.1 Tracking
    5. 7.5 Programming
      1. 7.5.1 Programming the Operating Frequency
      2. 7.5.2 Programming the Soft-Start Time
      3. 7.5.3 Using the Device for Clock Master/Slave Operation
      4. 7.5.4 Using the TPS40180 for Voltage Control Loop Master or Slave Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Single Output Synchronous Buck Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Inductor Selection
          2. 8.2.1.2.2 Output Capacitor Selection
          3. 8.2.1.2.3 Input Capacitor Selection
          4. 8.2.1.2.4 MOSFET Selection
          5. 8.2.1.2.5 Peripheral Component Design
            1. 8.2.1.2.5.1  Switching Frequency Setting (RT)
            2. 8.2.1.2.5.2  Output Voltage Setting (FB)
            3. 8.2.1.2.5.3  Current Sensing Network Design (CS+, CS-)
            4. 8.2.1.2.5.4  Overcurrent Protection (ILIM)
            5. 8.2.1.2.5.5  VREG (PVCC)
            6. 8.2.1.2.5.6  BP5
            7. 8.2.1.2.5.7  Phase Select (PSEL)
            8. 8.2.1.2.5.8  VSHARE (VSH)
            9. 8.2.1.2.5.9  Powergood (PGOOD)
            10. 8.2.1.2.5.10 Undervoltage Lockout (UVLO)
            11. 8.2.1.2.5.11 Clock Synchronization (CLKIO)
            12. 8.2.1.2.5.12 Bootstrap Capacitor
            13. 8.2.1.2.5.13 Soft Start (SS)
            14. 8.2.1.2.5.14 Remote Sense
            15. 8.2.1.2.5.15 Feedback Compensator Design
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Simultaneous Tracking With TPS40180 Devices
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 2-Phase Single Output With TPS40180
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Inductor Selection
          2. 8.2.3.2.2 Output Capacitor Selection
          3. 8.2.3.2.3 Input Capacitor Selection
          4. 8.2.3.2.4 Peripheral Component Design
            1. 8.2.3.2.4.1 PSEL Pin
            2. 8.2.3.2.4.2 CLKIO Pin
            3. 8.2.3.2.4.3 RT Pin
            4. 8.2.3.2.4.4 SS Pin
            5. 8.2.3.2.4.5 DIFFO Pin and FB Pin
            6. 8.2.3.2.4.6 COMP Pin
            7. 8.2.3.2.4.7 VSH Pin
            8. 8.2.3.2.4.8 Other Pins
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power Stage
      2. 10.1.2 Device Peripheral
      3. 10.1.3 PowerPad Layout™
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Device Nomenclature
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community 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

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The first design example describes the design process and component selection for a single-phase, synchronous buck, DC/DC converter using the TPS40180 device. The design process and component selection for a two-phase design are provided as well.

8.2 Typical Applications

8.2.1 Single Output Synchronous Buck Converter

Figure 32 illustrates the design process and component selection for a single output synchronous buck converter using TPS40180. The design goal parameters are given in Table 6. A list of symbol definitions is found in Device Nomenclature.

TPS40180 single_output_converter_schem_slvs753.gif Figure 32. Single-Output Converter Schematic

8.2.1.1 Design Requirements

Table 6 lists the design parameters for the single output configuration from 12-V to 1.5-V DC-to-DC converter using a TPS40180.

Table 6. Design Goal Parameters

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VIN Input voltage 10.8 12 13.2 V
VOUT Output voltage 1.5 V
VRIPPLE Output ripple IOUT = 20 A 30 mV
IOUT Output current 20 A
fSW Switching frequency 280 kHz

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Inductor Selection

The inductor is determined by the desired ripple current. The required inductor is calculated by Equation 19.

Equation 19. TPS40180 equation_19_slvs753.gif

Typically the peak-to-peak inductor current IRIPPLE is selected to be around 25% of the rated output current. In this design, IRIPPLE is targeted at 25% of IOUT. The calculated inductor is 0.95 µH and in practical a 1-µH inductor with 1.7-mΩ DCR from Vishay is selected. The real inductor ripple current is 4.7 A.

8.2.1.2.2 Output Capacitor Selection

The output capacitor is typically selected by the output load transient response requirement. Equation 20 estimates the minimum capacitor to reach the undervoltage requirement with load step-up. Equation 21 estimates the minimum capacitor for over voltage requirement with load step-down. When VIN(min) < 2 × VOUT, the minimum output capacitance can be calculated using Equation 20. Otherwise, Equation 21 is used.

Equation 20. TPS40180 equation_20_slvs753.gif
Equation 21. TPS40180 equation_21_slvs753.gif

In this design, VIN(min) is much larger than 2 × VOUT, so Equation 21 is used to determine the minimum capacitance. Based on a 8-A load transient with a maximum of 60-mV deviation, a minimum 356-µF output capacitor is required. Considering the capacitance variation and derating, four 220-µF, 4-V, SP capacitor are selected in the design to achieve sufficient margin. Each capacitor has an ESR of 5 mΩ.

Another criterion for capacitor selection is the output ripple voltage. The output ripple is determined mainly by the capacitance and the ESR. With an 880-µF output capacitance, the ripple voltage at the capacitor is calculated to be 1.5 mV. In the specification, the output ripple voltage should be less than 30 mV, so based on Equation 22, the required maximum ESR is 9.4 mΩ. The selected capacitors can meet this requirement.

Equation 22. TPS40180 equation_22_slvs753.gif

8.2.1.2.3 Input Capacitor Selection

The input voltage ripple depends on input capacitance and ESR. The minimum capacitor and the maximum ESR can be estimated by Equation 23 and Equation 24.

Equation 23. TPS40180 equation_23_slvs753.gif
Equation 24. TPS40180 equation_24_slvs753.gif

For this design, assume VRIPPLE(Cin) is 100 mV and VRIPPLE(CinESR) is 50 mV, so the calculated minimum capacitance is 89 µF and the maximum ESR is 2.3 mΩ. Choosing four 22-µF, 16-V, 2-mΩ ESR ceramic capacitors meets this requirement.

Another important thing for the input capacitor is the RMS ripple current rating. The RMS current in the input capacitor is estimated with Equation 25.

Equation 25. TPS40180 equation_25_slvs753.gif

where

  • D is the duty cycle

The calculated RMS current is 6.6 A. Each selected ceramic capacitor has a RMS current rating of 4.3 A, so it is sufficient to reach this requirement.

8.2.1.2.4 MOSFET Selection

The MOSFET selection determines the converter efficiency. In this design, the duty cycle is very small so that the high-side MOSFET is dominated with switching losses and the low-side MOSFET is dominated with conduction loss. To optimize the efficiency, choose smaller gate charge for the high-side MOSFET and smaller RDS(on) for the low-side MOSFET. RENESAS HAT2167H and HAT2164H are selected as the high-side and low-side MOSFET respectively. The power losses in the high-side MOSFET is calculated with the following equations.

The RMS current in the high-side MOSFET is Equation 26.

Equation 26. TPS40180 equation_26_slvs753.gif

The RDS(on)(sw) is 9.3 mΩ when the MOSFET gate voltage is 4.5 V. The conduction loss is Equation 27.

Equation 27. TPS40180 equation_27_slvs753.gif

The switching loss is Equation 28.

Equation 28. TPS40180 equation_28_slvs753.gif

The calculated total loss is the high-side MOSFET is Equation 29.

Equation 29. TPS40180 equation_29_slvs753.gif

The RMS current in the low-side MOSFET is Equation 30.

Equation 30. TPS40180 equation_30_slvs753.gif

The RDS(on)(sr) of each HAT2164 is 4.4 mΩ when the gate voltage is 4.5 V. Two HAT2164 FETs are used in this design.

The conduction loss in the low-side MOSFETs is Equation 31.

Equation 31. TPS40180 equation_31_slvs753.gif

The total power loss in the body diode is Equation 32.

Equation 32. TPS40180 equation_32_slvs753.gif

Therefore, the calculated total loss in the SR MOSFETs is Equation 33.

Equation 33. TPS40180 equation_33_slvs753.gif

8.2.1.2.5 Peripheral Component Design

8.2.1.2.5.1 Switching Frequency Setting (RT)

Equation 34. TPS40180 equation_34_slvs753.gif

In the design, a 95.3 kΩ resistor is selected. The actual switching frequency is 280 kHz.

8.2.1.2.5.2 Output Voltage Setting (FB)

Substitute the top resistor R1 with 10 kΩ in Equation 35, and then calculate the bottom bias resistor.

Equation 35. TPS40180 equation_35_slvs753.gif

8.2.1.2.5.3 Current Sensing Network Design (CS+, CS–)

Choosing C1 a value for 0.1 µF, and calculating R with Equation 36.

Equation 36. TPS40180 equation_36_slvs753.gif

8.2.1.2.5.4 Overcurrent Protection (ILIM)

ILIM pin is connected to VSH and VOUT pins with R1 and R2 respectively. Equation 8 and Equation 9 are used to calculate the overcurrent setting resistors. The DC over current rating is set at 28 A. The calculated values are 41 kΩ and 830 kΩ for R1 and R2 respectively. In the final design, R1 and R2 are chosen as 36.5 kΩ and
787 kΩ for temperature and other tolerances compensation.

8.2.1.2.5.5 VREG (PVCC)

A 4.7-µF capacitor is recommended to filter noise.

8.2.1.2.5.6 BP5

A 4.7-Ω resistor and 1-µF capacitor is placed between V REG and BP5 as a low-pass filter.

8.2.1.2.5.7 Phase Select (PSEL)

If the board is configured as a clock master for a multiphase application, an 8-phase CLKIO signal is generated if PSEL pin is open, and a 6-phase CLKIO signal is generated if PSEL is tied to ground with a 29.4-kΩ resistor. If the board is stacked as a slave for a multiphase application, a different resistor value is selected. The PSEL resistor selection is illustrated in the previous datasheet section.

8.2.1.2.5.8 VSHARE (VSH)

A 1-µF capacitor is tied from VSHARE to GND.

8.2.1.2.5.9 Powergood (PGOOD)

The PGOOD pin is tied to BP5 with a 10-kΩ resistor.

8.2.1.2.5.10 Undervoltage Lockout (UVLO)

UVLO is connected to the input voltage with a resistor divider. The two resistors have the same value of 10 kΩ. When the input voltage is higher than 2 V, the internal linear regulator is enabled.

8.2.1.2.5.11 Clock Synchronization (CLKIO)

CLKIO is floating as no clock synchronization required for single output configuration.

8.2.1.2.5.12 Bootstrap Capacitor

A bootstrap capacitor is connected between the BOOT and SW pin. The bootstrap capacitor depends on the total gate charge of the high-side MOSFET and the amount of droop allowed on the bootstrap capacitor (see Equation 37).

Equation 37. TPS40180 equation_37_slvs753.gif

Qg is 11 nC and is 0.2 V in the calculation. For this application, a 0.1-µF capacitor is selected.

8.2.1.2.5.13 Soft Start (SS)

To get about 1-ms soft-start time, a 22-nF capacitor is tied to SS pin (see Equation 38).

Equation 38. TPS40180 equation_38_slvs753.gif

ISS is the soft-start current which is 15-µA typically. VREF is the reference voltage, 0.7 V.

8.2.1.2.5.14 Remote Sense

VOUT and GSNS are connected to the remote sensing output connector. DIFFO is connected to the output voltage setting resistor divider. If the differential amplifier is not used, VOUT and GSNS are suggested to be grounded, and DIFFO is left open.

8.2.1.2.5.15 Feedback Compensator Design

Peak current mode control method is employed in the controller. A small signal model is developed from the COMP signal to the output (see Equation 39).

Equation 39. TPS40180 equation_39_slvs753.gif

The time constant is defined by Equation 40.

Equation 40. TPS40180 equation_40_slvs753.gif

Equation 40 is applied when the PWM pulse width is shorter than the current loop delay. The current loop delay is typically 100 ns.

Equation 41. TPS40180 equation_41_slvs753.gif

Equation 41 is applied when the PWM pulse width is longer than the current loop delay. The current loop delay is typically 100 ns. Equation 42 is used in this design because the PWM pulse width is much larger than the current loop delay. The low frequency pole is calculated by Equation 42.

Equation 42. TPS40180 equation_42_slvs753.gif

The ESR zero is calculated by Equation 43.

Equation 43. TPS40180 equation_43_slvs753.gif

In this design, at Type II compensator (Figure 33) is employed to compensate the loop.

TPS40180 type_ll_compensator_slvs753.gif Figure 33. Type II Compensator

The compensator transfer function is Equation 44.

Equation 44. TPS40180 equation_44_slvs753.gif

The loop gain function is Equation 45.

Equation 45. TPS40180 equation_45_slvs753.gif

Assume the desired crossover frequency is 25 kHz, then set the compensator zero about 1/10 of the crossover frequency and the compensator pole equal to the ESR zero. The compensator gain is then calculated to achieve the desired bandwidth. In this design, the compensator gain, pole and zero are selected using Equation 46 through Equation 49.

Equation 46. TPS40180 equation_46_slvs753.gif
Equation 47. TPS40180 equation_47_slvs753.gif
Equation 48. TPS40180 equation_48_slvs753.gif

From Equation 48, the compensator gain is solved as 4.5 × 105.

Equation 49. TPS40180 equation_49_slvs753.gif

Set R1 equal to 10 kΩ, and then calculate all the other components.

  • R2 = 40 kΩ
  • C1 = 22 pF
  • C2 = 1.6 nF

In the real laboratory practice, the final components are selected as following to increase the phase margin and reduce PWM jitter.

  • R1 = 10 kΩ
  • R2 = 39 kΩ
  • C1 = 22 pF
  • C2 = 2.7 nF

8.2.1.3 Application Curves

TPS40180 efficiency_curve_slvs753.gif Figure 34. Efficiency Curve
TPS40180 output_load_regulation_slvs753.gif Figure 35. Output Load Regulation

8.2.2 Simultaneous Tracking With TPS40180 Devices

TPS40180 additional_app_circuit_l_slvs753.gif Figure 36. Simultaneous Tracking With TPS40180

8.2.2.1 Design Requirements

The TPS40180 can function in a tracking mode, where the output tracks some other voltage. In the simultaneous tracking design, the output voltages of two TPS40180 blocks needs to rise up and fall down with the same slew rate.

8.2.2.2 Detailed Design Procedure

In Figure 36, the SS pin of Block II is connected to the output voltage of Block I via voltage divider. A value between 1 kΩ and 10 kΩ is suggested for the bottom. Here a 4.32-kΩ resistor is selected for bottom resistor. From Equation 12, the top resistor is calculated as 5.1 kΩ.

From Equation 13, a 220-nF capacitor is selected in parallel with the top resistor, and a 270-nF capacitor is selected in parallel with bottom resistor.

8.2.2.3 Application Curves

TPS40180 simultaneously_tracking_up_slvs753.gif Figure 37. Simultaneously Tracking Up
TPS40180 simultaneously_tracking_down_slvs753.gif Figure 38. Simultaneously Tracking Down

8.2.3 2-Phase Single Output With TPS40180

In Figure 39, Block I and Block II are configured as master and slave respectively.

TPS40180 2_phase_single_output_schem_slvs753.gif Figure 39. 2-Phase Single Output Schematic with TPS40180
VIN = 12 V, VOUT = 1.5 V, IOUT = 40 A

8.2.3.1 Design Requirements

Table 7 lists the design parameters for this example application.

Table 7. Design Goal Parameters

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VIN Input voltage 10.8 12 13.2 V
VOUT Output voltage 1.5 V
VRIPPLE Output ripple IOUT = 40 A 30 mV
IOUT Output current 40 A
fSW Switching frequency 280 kHz

8.2.3.2 Detailed Design Procedure

8.2.3.2.1 Inductor Selection

The inductor is determined by the desired inductor ripple current. Use Equation 19 to calculate the inductor value. In this design, IRIPPLE is targeted at 25% of phase current. The calculated inductor is 0.95 µH and in practical a 1-µH inductor with 1.7-mΩ DCR is selected. The real inductor ripple current is 4.7 A.

8.2.3.2.2 Output Capacitor Selection

The output capacitor is typically selected by the output load transient response requirement. Equation 21 in the single-phase design example is used. The inductor L in the equation is equal to the phase inductance divided by number of phases.

Based on a 40-A load transient with a maximum of 30 mV deviation, a minimum 711-µF output capacitor is required. Considering the capacitance variation and derating, eight 220-µF SP capacitors are selected in the design with sufficient margin. Each capacitor has an ESR of 5 mΩ.

Another criterion for capacitor selection is the output ripple voltage that is determined mainly by the capacitance and the ESR.

Due to the interleaving of channels, the total output ripple current is smaller than the ripple current from a single phase. The ripple cancellation factor is expressed in Equation 50. In this design, the ripple cancellation factor is 0.857.

Equation 50. TPS40180 equation1_slus660.gif

where

  • D is the duty cycle for a single phase
  • NPH is the number of active phases, here it is equal to 2
  • m = floor (NPH × D) is the maximum integer that does not exceed the (NPH × D), here m is 0

The output ripple current is then calculated in Equation 51. The maximum output ripple is with maximum input voltage. In this design, the maximum output ripple is calculated as 4.03 A.

Equation 51. TPS40180 equation4_slus660.gif

With 1.76-mF output capacitance, the ripple voltage from the capacitance is 1 mV. In the specification, the output ripple voltage should be less than 30 mV, so based on Equation 22, the required maximum ESR is 7.2 mΩ. The selected capacitors must meet this requirement.

8.2.3.2.3 Input Capacitor Selection

The input voltage ripple depends on the input capacitance and ESR. The minimum capacitor and the maximum ESR can be estimated by Equation 23 and Equation 24 in the single phase design example. The phase current should be used in the calculation.

8.2.3.2.4 Peripheral Component Design

8.2.3.2.4.1 PSEL Pin

Use Table 3 and Table 4 to configure PSEL pin. In this design, the PSEL pin of master controller is open to set 8 phase CLKIO. The CLKIO pin sends out a pulse train for interleaving with 45° phase separation. The PSEL pin of slave controller is connected to GND through 47-kΩ resistor to set 180° phase angle.

8.2.3.2.4.2 CLKIO Pin

The CLKIO pins of master and slave controllers must be connected together. A 10-kΩ resistor is connected from the CLKIO line to GND to ensure that the CLKIO line falls to GND quickly when the master controller is shutdown or powers off.

8.2.3.2.4.3 RT Pin

In this design, the RT pin of master controller is connected to GND through 95.3-kΩ resistor to set switching frequency at 280 kHz per phase. The RT pin of slave controller is connected to VDD.

8.2.3.2.4.4 SS Pin

The SS pin of master controller is connected to GND through 22-nF capacitor to get about 1-ms soft-start time. The SS pin of slave parts to VDD pin is connected to VDD pin.

8.2.3.2.4.5 DIFFO Pin and FB Pin

The DIFFO pin and FB pin of master controller are connected to feedback and compensation network. The DIFFO pin and FB pin of slave controller are open.

8.2.3.2.4.6 COMP Pin

The COMP pins of master and slave controller must be connected together.

8.2.3.2.4.7 VSH Pin

An individual VSH bypass capacitor is required by master and slave controller. The VSH pins of master and slave controllers must be connected together.

8.2.3.2.4.8 Other Pins

Follow the design procedure of single-phase design for other peripheral components design.

8.2.3.3 Application Curves

TPS40180 switch_node_CLKIO_waveforms_slvs753.gif Figure 40. Switch Node and CLKIO Waveforms
TPS40180 current_balance_0_A_slvs753.gif Figure 41. Current Balance at 0-A to 16-A Load
Step-Up, 2.5-A/µs Slew Rate