SLUSA48 June   2016 TPS51200-EP

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  Sink and Source Regulator (VO Pin)
      2. 7.3.2  Reference Input (REFIN Pin)
      3. 7.3.3  Reference Output (REFOUT Pin)
      4. 7.3.4  Soft-Start Sequencing
      5. 7.3.5  Enable Control (EN Pin)
      6. 7.3.6  Powergood Function (PGOOD Pin)
      7. 7.3.7  Current Protection (VO Pin)
      8. 7.3.8  UVLO Protection (VIN Pin)
      9. 7.3.9  Thermal Shutdown
      10. 7.3.10 Tracking Start-up and Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Low-Input Voltage Applications
      2. 7.4.2 S3 and Pseudo-S5 Support
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical VTT DIMM Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input Voltage Capacitor
        2. 8.2.2.2 VLDO Input Capacitor
        3. 8.2.2.3 Output Capacitor
        4. 8.2.2.4 Output Tolerance Consideration for VTT DIMM Applications
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
      1. 8.3.1 3.3-VIN, DDR2 Configuration
      2. 8.3.2 2.5-VIN, DDR3 Configuration
      3. 8.3.3 3.3-VIN, LP DDR3 or DDR4 Configuration
      4. 8.3.4 3.3-VIN, DDR3 Tracking Configuration
      5. 8.3.5 3.3-VIN, LDO Configuration
      6. 8.3.6 3.3-VIN, DDR3 Configuration with LFP
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Design Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Evaluation Modules
        2. 11.1.2.2 Spice Models
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 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 TPS51200-EP device is specifically designed to power up the memory termination rail (as shown in Figure 19). The DDR memory termination structure determines the main characteristics of the VTT rail, which is to be able to sink and source current while maintaining acceptable VTT tolerance. See Figure 20 for typical characteristics for a single memory cell.

8.2 Typical VTT DIMM Applications

TPS51200-EP v08022_lus812.gif Figure 19. Typical Application Diagram for DDR3 VTT DIMM Using TPS51200-EP

8.2.1 Design Requirements

Use the information listed in Table 1 as the design parameters.

Table 1. DDR, DDR2, DDR3, and LP DDR3 Termination Technology and Differences

PARAMETER DDR DDR2 DR3 LOW-POWER DDR3
FSB data rates 200, 266, 333 and 400 MHz 400, 533, 677 and 800 MHz 800, 1066, 1330 and 1600 MHz Same as DDR3
Termination Motherboard termination to VTT for all signals On-die termination for data group. VTT termination for address, command and control signals. On-die termination for data group. VTT termination for address, command and control signals. Same as DDR3
Termination current demand Max sink and source transient currents of up to 2.6 A to 2.9 A Not as demanding
  • Only 34 signals (address, command, control) tied to VTT
  • ODT handles data signals
Less than 1 A of burst current		 Not as demanding
  • Only 34 signals (address, command, control) tied to VTT
  • ODT handles data signals
Less than 1 A of burst current		 Same as DDR3
Voltage level 2.5-V core and I/O 1.25-V VTT 1.8-V core and I/O 0.9-V VTT 1.5-V core and I/O 0.75-V VTT 1.2-V core and I/O 0.6-V VTT

8.2.2 Detailed Design Procedure

8.2.2.1 Input Voltage Capacitor

Add a ceramic capacitor, with a value between 1-μF and 4.7-μF, placed close to the VIN pin, to stabilize the bias supply (2.5-V rail or 3.3-V rail) from any parasitic impedance from the supply.

8.2.2.2 VLDO Input Capacitor

Depending on the trace impedance between the VLDOIN bulk power supply to the device, a transient increase of source current is supplied mostly by the charge from the VLDOIN input capacitor. Use a 10-μF (or greater) ceramic capacitor to supply this transient charge. Provide more input capacitance as more output capacitance is used at the VO pin. In general, use one-half of the COUT value for input.

8.2.2.3 Output Capacitor

For stable operation, the total capacitance of the VO output pin must be greater than 20 μF. Attach 3 × 10-μF ceramic capacitors in parallel to minimize the effect of equivalent series resistance (ESR) and equivalent series inductance (ESL). If the ESR is greater than 2 mΩ, insert an RC filter between the output and the VOSNS input to achieve loop stability. The RC filter time constant should be almost the same as or slightly lower than the time constant of the output capacitor and its ESR.

8.2.2.4 Output Tolerance Consideration for VTT DIMM Applications

Figure 20 shows the typical characteristics for a single memory cell.

TPS51200-EP v08023_lus812.gif Figure 20. DDR Physical Signal System Bi-Directional SSTL Signaling

In Figure 20, when Q1 is on and Q2 is off:

  • Current flows from VDDQ via the termination resistor to VTT
  • VTT sinks current

In Figure 20, when Q2 is on and Q1 is off:

  • Current flows from VTT via the termination resistor to GND
  • VTT sources current

Because VTT accuracy has a direct impact on the memory signal integrity, it is imperative to understand the tolerance requirement on VTT. Equation 1 applies to both DC and AC conditions and is based on JEDEC VTT specifications for DDR and DDR2 (JEDEC standard: DDR JESD8-9B May 2002; DDR2 JESD8-15A Sept 2003).

Equation 1. VVTTREF – 40 mV < VVTT < VVTTREF + 40 mV

The specification itself indicates that VTT must keep track of VTTREF for proper signal conditioning.

The TPS51200-EP ensures the regulator output voltage to be as shown in Equation 2, which applies to both DC and AC conditions.

Equation 2. VVTTREF –25 mV < VVTT < VVTTREF + 25 mV

where

  • –2 A < IVTT < 2 A

The regulator output voltage is measured at the regulator side, not the load side. The tolerance is applicable to DDR, DDR2, DDR3, Low Power DDR3, and DDR4 applications (see Table 1 for detailed information). To meet the stability requirement, a minimum output capacitance of 20 μF is needed. Considering the actual tolerance on the MLCC capacitors, 3 × 10-μF ceramic capacitors sufficiently meet the VTT accuracy requirement.

The TPS51200-EP device uses transconductance (gM) to drive the LDO. The transconductance and output current of the device determine the voltage droop between the reference input and the output regulator. The typical transconductance level is 250 S at 2 A and changes with respect to the load in order to conserve the quiescent current (that is, the transconductance is very low at no load condition). The (gM) LDO regulator is a single pole system. Only the output capacitance determines the unity gain bandwidth for the voltage loop, as a result of the bandwidth nature of the transconductance (see Equation 3).

Equation 3. TPS51200-EP q_fugbw_slus812.gif

where

  • ƒUGBW is the unity gain bandwidth
  • gM is transconductance
  • COUT is the output capacitance

Consider these two limitations to this type of regulator that come from the output bulk capacitor requirement. In order to maintain stability, the zero location contributed by the ESR of the output capacitors must be greater than the –3-dB point of the current loop. This constraint means that higher ESR capacitors should not be used in the design. In addition, the impedance characteristics of the ceramic capacitor should be well understood in order to prevent the gain peaking effect around the transconductance (gM) –3-dB point because of the large ESL, the output capacitor, and the parasitic inductance of the VO pin voltage trace.

8.2.3 Application Curves

Figure 21 shows the bode plot simulation for this DDR3 design example of the TPS51200-EP device.

The unity-gain bandwidth is approximately 1 MHz and the phase margin is 52°. When the 0-dB level is crossed, the gain peaks because of the ESL effect. However, the peaking maintains a level well below 0 dB.

Figure 22 shows the load regulation and Figure 23 shows the transient response for a typical DDR3 configuration. When the regulator is subjected to ±1.5-A load step and release, the output voltage measurement shows no difference between the DC and AC conditions.

TPS51200-EP bode_plot_ddr3_wide_sluse812.gif
VIN = 3.3 V VVLDOIN = 1.5 V VVO = 0.75 V
IIO = 2 A 3 × 10-μF capacitors ESR = 2.5 mΩ
ESL = 800 pH
Figure 21. DDR3 Design Example Bode Plot
TPS51200-EP D003_SLUSA48.gif
VVIN = 3.3 V DDR3
Figure 22. Load Regulation
TPS51200-EP transient_wave_slus812.png Figure 23. Transient Waveform

8.3 System Examples

8.3.1 3.3-VIN, DDR2 Configuration

This design example describes a 3.3-VIN, DDR2 configuration application.

TPS51200-EP v08028_3p3_Vin_DDR2_slusa48.gif Figure 24. 3.3-VIN, DDR2 Configuration

Table 2. 3.3-VIN, DDR2 Configuration List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1, R2 Resistor 10 kΩ
R3 100 kΩ
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata

8.3.2 2.5-VIN, DDR3 Configuration

This design example describes a 2.5-VIN, DDR3 configuration application.

TPS51200-EP v08030_2p5_Vin_DDR3_slusa48.gif Figure 25. 2.5-VIN, DDR3 Configuration

Table 3. 2.5-VIN, DDR3 Configuration List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1, R2 Resistor 10 kΩ
R3 100 kΩ
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata

8.3.3 3.3-VIN, LP DDR3 or DDR4 Configuration

This design example describes a 3.3-VIN, LP DDR3 or DDR4 configuration application.

TPS51200-EP v08031_3p3_Vin_LPDDR3_DDR4_slusa48.gif Figure 26. 3.3-VIN, LP DDR3 or DDR4 Configuration

Table 4. 3.3-VIN, LP DDR3 or DDR4 Configuration List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1, R2 Resistor 10 kΩ
R3 100 kΩ
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata

8.3.4 3.3-VIN, DDR3 Tracking Configuration

This design example describes a 3.3-VIN, DDR3 tracking configuration application.

TPS51200-EP v08032_3p3_Vin_DDR3_tracking_slusa48.gif Figure 27. 3.3-VIN, DDR3 Tracking Configuration

Table 5. 3.3-VIN, DDR3 Tracking Configuration List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1, R2 Resistor 10 kΩ
R3 100 kΩ
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata

8.3.5 3.3-VIN, LDO Configuration

This design example describes a 3.3-VIN, LDO configuration application.

TPS51200-EP v08033_3p3_Vin_LDO_slusa48.gif Figure 28. 3.3-VIN, LDO Configuration

Table 6. 3.3-VIN, LDO Configuration List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1 Resistor 3.86 kΩ
R2 10 kΩ
R3 100 kΩ
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata

8.3.6 3.3-VIN, DDR3 Configuration with LFP

This design example describes a 3.3-VIN, DDR3 configuration with LFP application.

TPS51200-EP v08034_3p3_Vin_DDR3_LFP_slusa48.gif Figure 29. 3.3-VIN, DDR3 Configuration with LFP

Table 7. 3.3-VIN, DDR3 Configuration with LFP List of Materials

REFERENCE DESIGNATOR DESCRIPTION SPECIFICATION PART NUMBER MANUFACTURER
R1, R2 Resistor 10 kΩ
R3 100 kΩ
R4(1)
C1, C2, C3 Capacitor 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C4 1000 pF
C5 0.1 μF
C6 4.7 μF, 6.3 V GRM21BR60J475KA11L Murata
C7, C8 10 μF, 6.3 V GRM21BR70J106KE76L Murata
C9(1)
(1) Choose values for R4 and C9 to reduce the parasitic effect of the trace (between VO and the output MLCCs) and the output capacitors (ESR and ESL).