SLVS585E July   2005  – June 2015 TPS62110 , TPS62111 , TPS62112 , TPS62113

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 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 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Enable
      2. 9.3.2 Low-Battery Detector (Standard Version)
      3. 9.3.3 Enable/Low-Battery Detector - Enhanced Version (TPS62113 Only)
      4. 9.3.4 Power Good Comparator
      5. 9.3.5 Undervoltage Lockout
      6. 9.3.6 Synchronization
      7. 9.3.7 Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Soft Start
      2. 9.4.2 Constant-Frequency Mode of Operation (Sync = High)
      3. 9.4.3 Power Save Mode of Operation (Sync = Low)
      4. 9.4.4 100% Duty-Cycle, Low-Dropout Operation
      5. 9.4.5 No-Load Operation
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Standard Connection for Adjustable Version
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 External Component Selection
          2. 10.2.1.2.2 Inductor Selection
          3. 10.2.1.2.3 Output Capacitor Selection
          4. 10.2.1.2.4 Input Capacitor Selection
          5. 10.2.1.2.5 Feedforward Capacitor Selection
          6. 10.2.1.2.6 Recommended Capacitors
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Standard Connection for Fixed-Voltage Version
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
        3. 10.2.2.3 Application Curves
    3. 10.3 System Examples
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Related Links
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

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10 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.

10.1 Application Information

The TPS6211x devices are a family of low-noise synchronous step-down DC-DC converters that are ideally suited for systems powered from a 2- to 4-cell Li-ion battery or from a 12-V or 15-V rail.

10.2 Typical Applications

10.2.1 Standard Connection for Adjustable Version

TPS62110 TPS62111 TPS62112 TPS62113 evm_sch_lvs585.gif
For an output voltage lower than 2.5 V, TI recommends an output capacitor of 33 μF or greater to improve load transient performance.
Figure 6. Standard Connection for Adjustable Version

10.2.1.1 Design Requirements

The design guidelines provide a component selection to operate the device within the Recommended Operating Conditions.

Table 1. Bill of Materials for the Adjustable Version

REFERENCE PART NUMBER VALUE MANUFACTURER
Ci C3225X5R1E106K 10 µF TDK
Co C3225X7R1C226M 22 µF TDK
L1 SLF7032T-6R8M1R6 6.8 µH TDK
C1 TMK212B7105KG-T 1 µF Taiyo Yuden
IC1 TPS62110 - Texas Instruments
R1 generic metal film resistor; tolerance 1% 220 kΩ (depending on desired output voltage) —
R2 generic metal film resistor; tolerance 1% 390 kΩ (depending on desired output voltage) —
R3, R4 generic metal film resistor; tolerance 1% 1 MΩ —
R5 generic metal film resistor; tolerance 1% open —
R6 generic metal film resistor; tolerance 1% 261 kΩ —
C(ff) generic ceramic capacitor; COG 10 pF (depending on output voltage) —

10.2.1.2 Detailed Design Procedure

The graphs were generated using the EVM with the setup according to Figure 6, unless otherwise noted. Graphs for an output voltage of 1.5 V and 1.8 V were generated using the TPS62110 device with the output voltage dividers adjusted according Table 2.

Equation 3. TPS62110 TPS62111 TPS62112 TPS62113 q7_vout_lvs585.gif
VFB = 1.153 V

Table 2. Recommended Resistors

OUTPUT VOLTAGE R1 R2 NOMINAL VOLTAGE TYPICAL Cff
9 V 680 kΩ 100 kΩ 8.993 V 22 pF
5 V 510 kΩ 150 kΩ 5.073 V 10 pF
3.3 V 560 kΩ 300 kΩ 3.305 V 10 pF
2.5 V 390 kΩ 330 kΩ 2.515 V 10 pF
1.8 V 220 kΩ 390 kΩ 1.803 V 10 pF
1.5 V 100 kΩ 330 kΩ 1.502 V 10 pF

10.2.1.2.1 External Component Selection

The control loop of the TPS6211x family of devices requires a certain value for the output inductor and the output capacitor for stable operation. As long as the nominal value of L × C ≥ 6.2 µH × 22 µF, the control loop has enough phase margin and the device is stable. Reducing the inductor value without increasing the output capacitor (or vice versa) may cause stability problems. There are applications where it may be useful to increase the value of the output capacitor, and so on, for a low-transient output-voltage change. From a stability point of view, the inductor value could be decreased to keep the L × C product constant. However, there are drawbacks if the inductor value is decreased. A low inductor value causes a high inductor ripple current, and therefore reduces the maximum DC output current. Table 3 gives the advantages and disadvantages when designing the inductor and output capacitor.

Table 3. Advantages and Disadvantages When Designing the Inductor and Output Capacitor

INFLUENCE ON STABILITY ADVANTAGE DISADVANTAGE
Increase Cout (>22 µF) Uncritical Less output voltage ripple None
Less output voltage overshoot / undershoot during load transient
Decrease Cout (<22 µF) Critical
Increase inductor value >6.8 µH also 		None Higher-output voltage ripple
High-output voltage overshoot / undershoot during load transient
Less gain and phase margin
Increase L (>6.8 µH) Uncritical Less inductor current ripple More energy stored in the inductor → higher voltage overshoot during load transient
Higher DC output current possible if operated close to the current limit Smaller current rise → higher voltage undershoot during load transient → do not decrease the value of Cout due to these effects
Decrease L (<6.8 µH) Critical Small voltage overshoot and undershoot during load transient High inductor current ripple especially at high input voltage and low output voltage
Increase output capacitor value > 22 µF also

10.2.1.2.2 Inductor Selection

As shown in Table 3, the inductor value can be increased to greater values. For good performance, the peak-to-peak inductor-current ripple should be less than 30% of the maximum DC output current. Especially at input voltages greater than 12 V, it makes sense to increase the inductor value to keep the inductor-current ripple low. In such applications, the inductor value can be increased to 10 µH or 22 µH. Values greater than 22 µH should be avoided to keep the voltage overshoot during load transient in an acceptable range.

After choosing the inductor value, two additional inductor parameters should be considered:

  • Current rating of the inductor
  • DC resistance
The DC resistance of the inductance directly influences the efficiency of the converter. Therefore, an inductor with lowest DC resistance should be selected for highest efficiency. To avoid saturation of the inductor, the inductor should be rated at least for the maximum output current plus the inductor ripple current which is calculated using Equation 4.

Equation 4. TPS62110 TPS62111 TPS62112 TPS62113 q3_deltail_lvs585.gif

where

  • f = Switching frequency (1000 kHz typical)
  • L = Inductor value
  • ΔIL = Peak-to-peak inductor ripple current
  • IL(max) = Maximum inductor current

The highest inductor current occurs at maximum VI. A more conservative approach is to select the inductor current rating just for the maximum switch current of the TPS6211x, which is 2.4 A (typically). See Table 4 for recommended inductors.

Table 4. List of Inductors

MANUFACTURER PART NO. INDUCTANCE DC RESISTANCE SATURATION CURRENT
Coilcraft MSS6132-682 6.8 µH 65 mΩ (maximum) 1.5 A
HA3808-AL 6.8 µH 99 mΩ (typical) 4.4 A
Epcos B82462G4682M 6.8 µH 50 mΩ (maximum) 1.5 A
Sumida CDRH5D28-6R2 6.2 µH 33 mΩ (typical) 1.8 A
TDK SLF6028T-6R8M1R5 6.8 µH 35 mΩ (typical) 1.5 A
SLF7032T-6R8M1R6 6.8 µH 41 mΩ (typical) 1.6 A
Wurth 7447789006 6.8 µH 44 mΩ (typical) 2.75 A
7447779006 6.8 µH 33 mΩ (typical) 3.3 A
744053006 6.2 µH 45 mΩ (typical) 1.8 A

10.2.1.2.3 Output Capacitor Selection

A 22-μF (typical) output capacitor is needed with a 6.8-μH inductor. For an output voltage greater than 5 V, a 33-μF (minimum) output capacitor is required for stability. For best performance, a low-ESR ceramic output capacitor is needed.

The RMS ripple current is calculated using Equation 5.

Equation 5. TPS62110 TPS62111 TPS62112 TPS62113 q4_irmsco_lvs585.gif

The overall output ripple voltage is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor:

Equation 6. TPS62110 TPS62111 TPS62112 TPS62113 q5_deltaout_lvs585.gif

where

  • the highest output voltage ripple occurs at the highest input voltage VI.

10.2.1.2.4 Input Capacitor Selection

The nature of the buck converter is a pulsating input current; therefore, a low ESR input capacitor is required for best input voltage filtering and for minimizing the interference with other circuits caused by high input voltage spikes. The input capacitor should have a minimum value of 10 µF and can be increased without any limit for better input voltage filtering. The input capacitor should be rated for the maximum input ripple current and is calculated using Equation 7.

Equation 7. TPS62110 TPS62111 TPS62112 TPS62113 q6_irms_lvs585.gif

The worst-case RMS ripple current occurs at D = 0.5 and is calculated as: IRMS = IO/2. Ceramic capacitors show a good performance because of their low ESR value, and they are less sensitive against voltage transients compared to tantalum capacitors. Place the input capacitor as close as possible to the VIN and PGND pins of the IC for best performance.

An additional 1-µF input capacitor is required from VINA to AGND. VIN and VINA must be connected to the same source. TI does not recommend an RC filter from VIN to VINA.

10.2.1.2.5 Feedforward Capacitor Selection

The feedforward capacitor (Cff) is needed to compensate for parasitic capacitance from the feedback pin to GND. Typically, a value of 4.7 pF to 22 pF is needed for an output voltage divider with a equivalent resistance (R1 in parallel with R2) in the 150-kΩ range. The value can be chosen based on best transient performance and lowest output voltage ripple in PFM mode.

10.2.1.2.6 Recommended Capacitors

TI recommends using only X5R or X7R ceramic capacitors as input and output capacitors. Ceramic capacitors show a DC-bias effect. This effect reduces the effective capacitance when a DC-bias voltage is applied across a ceramic capacitor, as on the output and input capacitor of a DC-DC converter. The effect may lead to a significant capacitance drop, especially for high input and output voltages and small capacitor packages. See the manufacturer's data sheet about the performance with a DC bias voltage applied. It may be necessary to choose a higher voltage rating or nominal capacitance value to get the required value at the operating point. The capacitors listed in Table 5 have been tested with the TPS6211x devices with good performance.

Table 5. List of Capacitors

MANUFACTURER PART NUMBER SIZE VOLTAGE CAPACITANCE TYPE
Taiyo Yuden TMK316BJ106KL 1206 25 V 10 µF Ceramic
EMK325BJ226KM 1210 16 V 22 µF
TDK C3225X5R1E106M 1210 25 V 10 µF Ceramic
C3225X7R1C226M 16 V 22 µF
C3216X5R1E106MT 1206 25 V 10 µF

10.2.1.3 Application Curves

TPS62110 TPS62111 TPS62112 TPS62113 eff_18v_io_pwm_lvs585.gifFigure 7. TPS62110 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_15v_io_pwm_lvs585.gifFigure 9. TPS62110 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_18v_io_pfm_lvs585.gifFigure 8. TPS62110 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_15v_io_pfm_lvs585.gifFigure 10. TPS62110 Efficiency vs Output Current

10.2.2 Standard Connection for Fixed-Voltage Version

TPS62110 TPS62111 TPS62112 TPS62113 fxd_cap_lvs585.gifFigure 11. Standard Connection for Fixed-Voltage Version

10.2.2.1 Design Requirements

The design guidelines provide a component selection to operate the device within the Recommended Operating Conditions.

Table 6. Bill of Materials for the Fixed Voltage Versions

REFERENCE PART NUMBER VALUE MANUFACTURER
Ci C3225X5R1E106K 10 µF TDK
Co C3225X7R1C226M 22 µF TDK
L1 SLF7032T-6R8M1R6 6.8 µH TDK
C1 TMK212B7105KG-T 1 µF Taiyo Yuden
IC1 TPS62112 — Texas Instruments
R3 generic metal film resistor; tolerance 1% 1 MΩ —

10.2.2.2 Detailed Design Procedure

The graphs were generated using the EVM with the setup according to Figure 6, unless otherwise noted. Graphs for an output voltage of 5 V and 3.3 V were generated using the TPS62111 and TPS62112 devices with R1 = 0 Ω and R2 = open.

10.2.2.3 Application Curves

TPS62110 TPS62111 TPS62112 TPS62113 eff_5v_io_pwm_lvs585.gifFigure 12. TPS62112 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_3v_io_pwm_lvs585.gifFigure 14. TPS62111 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_5v_io_pfm_lvs585.gifFigure 13. TPS62112 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_3v_io_pfm_lvs585.gifFigure 15. TPS62111 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 eff_3v_sync_slvs585.gifFigure 16. TPS62111 Efficiency vs Output Current
TPS62110 TPS62111 TPS62112 TPS62113 load_33tran_lvs585.gif
Figure 18. TPS62111 Load Transient
TPS62110 TPS62111 TPS62112 TPS62113 start_up111_lvs585.gifFigure 20. TPS62111 Start-up Timing
TPS62110 TPS62111 TPS62112 TPS62113 line_33tran_lvs585.gif
Figure 17. TPS62111 Line Transient
TPS62110 TPS62111 TPS62112 TPS62113 vo_rip111_lvs585.gifFigure 19. TPS62111 Output Ripple

10.3 System Examples

The TPS62110 device can be used within an adjustable output voltage range from 1.2 V to 16 V. Figure 21 shows and application example with 9-V output.

TPS62110 TPS62111 TPS62112 TPS62113 app_cir9v_lvs585.gif
A. For an output voltage greater than 5 V, an output capacitor of 33 μF minimum is required for stability.
Figure 21. Application With 9-V Output