SLVS417F March   2002  – June 2015 TPS62200 , TPS62201 , TPS62202 , TPS62203 , TPS62204 , TPS62205 , TPS62207 , TPS62208

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Undervoltage Lockout
      2. 7.3.2 Dynamic Voltage Positioning
      3. 7.3.3 Soft Start
      4. 7.3.4 Low Dropout Operation 100% Duty Cycle
      5. 7.3.5 Enable
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power Save Mode Operation
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Adjustable Output Voltage Version
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Output Capacitor Selection
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
      1. 8.3.1 Various Output Voltages
      2. 8.3.2 Adjustable Output Voltage Version Set to 1.5 V
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Related Links
    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

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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 TPS6220x devices are a family of high-efficiency synchronous step-down converters ideally suited for portable systems powered by 1-cell Li-Ion or 3-cell NiMH/NiCd batteries. The devices are also suitable to operate from a standard 3.3-V or 5-V voltage rail.

8.2 Typical Application

TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 ai_ta_cir_lvs417.gifFigure 5. Typical Application Circuit for the Adjustable Output Voltage

8.2.1 Design Requirements

The Detailed Design Procedure provides a component selection to operate the device within the Recommended Operating Conditions.

8.2.2 Detailed Design Procedure

8.2.2.1 Adjustable Output Voltage Version

When the adjustable output voltage version TPS62200 is used, the output voltage is set by the external resistor-divider. See Figure 5.

The output voltage is calculated as:

Equation 4. TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 Q4_Vout_slvs417.gif

where

  • R1 + R2 ≤ 1 MΩ and internal reference voltage V(ref)typ = 0.5 V.

R1 + R2 should not be greater than 1 MΩ for reasons of stability. To keep the operating quiescent current to a minimum, the feedback resistor-divider should have high impedance with R1+R2 ≤ 1 MΩ. Because of the high impedance and the low reference voltage of Vref = 0.5 V, the noise on the feedback pin (FB) needs to be minimized. Using a capacitive divider C1 and C2 across the feedback resistors minimizes the noise at the feedback without degrading the line or load transient performance.

C1 and C2 should be selected as:

Equation 5. TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 Q5_C1_slvs417.gif

where

  • R1 = upper resistor of voltage divider.
  • C1 = upper capacitor of voltage divider.

For C1 a value should be chosen that comes closest to the calculated result.

Equation 6. TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 Q6_C2_slvs417.gif

where

  • R2 = lower resistor of voltage divider.
  • C2 = lower capacitor of voltage divider.

For C2 the selected capacitor value should always be selected larger than the calculated result. For example, in Figure 5 for C2, 100 pF are selected for a calculated result of C2 = 86.17 pF.

If quiescent current is not a key design parameter, C1 and C2 can be omitted, and a low-impedance feedback divider must be used with R1+R2 <100 kΩ. This design reduces the noise available on the feedback pin (FB) as well, but increases the overall quiescent current during operation.

8.2.2.2 Inductor Selection

The TPS6220x device is optimized to operate with a typical inductor value of 10 µH.

For high efficiencies, the inductor should have a low DC resistance to minimize conduction losses. Although the inductor core material has less effect on efficiency than its DC resistance, an appropriate inductor core material must be used.

The inductor value determines the inductor ripple current. The larger the inductor value, the smaller the inductor ripple current, and the lower the conduction losses of the converter. On the other hand, larger inductor values cause a slower load transient response. Usually the inductor ripple current, as calculated below, is around 20% of the average output current.

To avoid saturation of the inductor, the inductor should be rated at least for the maximum output current of the converter plus the inductor ripple current that is calculated as:

Equation 7. TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 Q7_delta_slvs417.gif

where

  • f = switching frequency (1 MHz typical, 650 kHz minimal).
  • L = inductor value.
  • ΔIL = peak-to-peak inductor ripple current.
  • ILmax = maximum inductor current.

The highest inductor current occurs at maximum Vin.

A more conservative approach is to select the inductor current rating just for the maximum switch current of 670 mA. Refer to Table 2 for inductor recommendations.

Table 2. Recommended Inductors

INDUCTOR VALUE COMPONENT SUPPLIER COMMENTS
10 µH
10 µH
10 µH
10 µH
Sumida CDRH5D28-100
Sumida CDRH5D18-100
Sumida CDRH4D28-100
Coilcraft DO1608-103
High efficiency
6.8 µH
10 µH
10 µH
10 µH
10 µH
Sumida CDRH3D16-6R8
Sumida CDRH4D18-100
Sumida CR32-100
Sumida CR43-100
Murata LQH4C100K04
Smallest solution

8.2.2.3 Input Capacitor Selection

Because the buck converter has a pulsating input current, a low ESR input capacitor is required. This results in the best input voltage filtering and minimizing the interference with other circuits caused by high input voltage spikes. Also the input capacitor must be sufficiently large to stabilize the input voltage during heavy load transients. For good input voltage filtering, usually a 4.7-µF input capacitor is sufficient. The capacitor can be increased without any limit for better input-voltage filtering. If ceramic output capacitors are used, the capacitor RMS ripple current rating always meets the application requirements.

Ceramic capacitors show a good performance because of the low ESR value, and they are less sensitive against voltage transients and spikes compared to tantalum capacitors.

Place the input capacitor as close as possible to the input pin of the device for best performance (refer to Table 3 for recommended components).

8.2.2.4 Output Capacitor Selection

The advanced fast response voltage mode control scheme of the TPS6220x allows the use of tiny ceramic capacitors with a value of 10 µF without having large output voltage under and overshoots during heavy load transients.

Ceramic capacitors with low ESR values have the lowest output voltage ripple and are therefore recommended. If required, tantalum capacitors may be used as well (refer to Table 3 for recommended components).

At nominal load current the device operates in PWM mode and the overall output voltage ripple 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 8. TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 Q8_deltaV_slvs417.gif

where

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

At light load currents, the device operates in power save mode, and the output voltage ripple is independent of the output capacitor value. The output voltage ripple is set by the internal comparator thresholds. The typical output voltage ripple is 1% of the output voltage Vo.

Table 3. Recommended Capacitors

CAPACITOR VALUE CASE SIZE COMPONENT SUPPLIER COMMENTS
4.7 µF 0805 Taiyo Yuden JMK212BY475MG Ceramic
10 µF 0805 Taiyo Yuden JMK212BJ106MG
TDK C12012X5ROJ106K
Ceramic
Ceramic
10 µF 1206 Taiyo Yuden JMK316BJ106KL
TDK C3216X5ROJ106M
Ceramic
22 µF 1210 Taiyo Yuden JMK325BJ226MM Ceramic

8.2.3 Application Curves

TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_effic_lvs417.gif
Figure 6. Efficiency vs Load Current
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_3effic_lvs417.gif
Figure 8. Efficiency vs Load Current
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_freq_lvs417.gif
Figure 10. Frequency vs Temperature
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_line_res_lvs417.png
Figure 12. Line Transient Response
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_pwr_sv_lvs417.png
Figure 14. Power Save Mode Operation
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_2effic_lvs417.gif
Figure 7. Efficiency vs Load Current
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_4effic_lvs417.gif
Figure 9. Efficiency vs Input Voltage
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_out_volt_lvs417.gif
Figure 11. Output Voltage vs Output Current
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_load_res_lvs417.png
Figure 13. Load Transient Response
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 tc_startup_lvs417.png
Figure 15. Start-Up

8.3 System Examples

8.3.1 Various Output Voltages

TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 ai_18fixed_lvs417.gifFigure 16. Li-Ion to 1.8-V Fixed Output Voltage Version
TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 ai_15adj_lvs417.gifFigure 17. 1.8 V Fixed Output Voltage Version Using 4.7-µH Inductor

8.3.2 Adjustable Output Voltage Version Set to 1.5 V

TPS62200 TPS62201 TPS62202 TPS62203 TPS62204 TPS62205 TPS62207 TPS62208 ai_lion18_lvs417.gifFigure 18. Adjustable Output Voltage Version Set to 1.5 V