JAJS536I October   2002  – December 2016 TPS61040 , TPS61041

PRODUCTION DATA.  

  1. 特長
  2. アプリケーション
  3. 概要
  4. 改訂履歴
  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 Peak Current Control
      2. 7.3.2 Soft Start
      3. 7.3.3 Enable
      4. 7.3.4 Undervoltage Lockout
      5. 7.3.5 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 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 Inductor Selection, Maximum Load Current
        2. 8.2.2.2 Setting the Output Voltage
        3. 8.2.2.3 Line and Load Regulation
        4. 8.2.2.4 Output Capacitor Selection
        5. 8.2.2.5 Input Capacitor Selection
        6. 8.2.2.6 Diode Selection
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 デベロッパー・ネットワークの製品に関する免責事項
    2. 11.2 関連リンク
    3. 11.3 コミュニティ・リソース
    4. 11.4 商標
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 用語集
  12. 12メカニカル、パッケージ、および注文情報

パッケージ・オプション

デバイスごとのパッケージ図は、PDF版データシートをご参照ください。

メカニカル・データ(パッケージ|ピン)
  • DBV|5
  • DRV|6
サーマルパッド・メカニカル・データ
発注情報

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.

Application Information

The TPS6104x is designed for output voltages up to 28 V with an input voltage range of 1.8 V to 6 V and a switch peak current limit of 400 mA (250 mA for the TPS61041). The device operates in a pulse-frequency-modulation (PFM) scheme with constant peak current control. This control scheme maintains high efficiency over the entire load current range, and with a switching frequency up to 1 MHz, the device enables the use of very small external components. The following section provides a step-by-step design approach for configuring the TPS61040 as a voltage regulating boost converter for LCD bias power supply, as shown in Figure 12.

Typical Application

The following section provides a step-by-step design approach for configuring the TPS611040 as a voltage regulating boost converter for LCD bias supply, as shown in Figure 12.

TPS61040 TPS61041 ai_lcd_lvs413.gif Figure 12. LCD Bias Supply

Design Requirements

Table 2. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input Voltage 1.8 V to 6 V
Output Voltage 18 V
Output Current 10 mA

Detailed Design Procedure

Inductor Selection, Maximum Load Current

Because the PFM peak current control scheme is inherently stable, the inductor value does not affect the stability of the regulator. The selection of the inductor together with the nominal load current, input and output voltage of the application determines the switching frequency of the converter. Depending on the application, inductor values from 2.2 μH to 47 μH are recommended. The maximum inductor value is determined by the maximum on time of the switch, typically 6 μs. The peak current limit of 400 mA/250 mA (typically) should be reached within this 6-μs period for proper operation.

The inductor value determines the maximum switching frequency of the converter. Therefore, select the inductor value that ensures the maximum switching frequency at the converter maximum load current is not exceeded. The maximum switching frequency is calculated by the following formula:

Equation 2. TPS61040 TPS61041 Q2_lvs413.gif

where

  • IP = Peak current as described in Peak Current Control
  • L = Selected inductor value
  • VIN(min) = The highest switching frequency occurs at the minimum input voltage

If the selected inductor value does not exceed the maximum switching frequency of the converter, the next step is to calculate the switching frequency at the nominal load current using the following formula:

Equation 3. TPS61040 TPS61041 Q3_lvs413.gif

where

  • IP = Peak current as described in Peak Current Control
  • L = Selected inductor value
  • Iload = Nominal load current
  • Vd = Rectifier diode forward voltage (typically 0.3 V)

A smaller inductor value gives a higher converter switching frequency, but lowers the efficiency.

The inductor value has less effect on the maximum available load current and is only of secondary order. The best way to calculate the maximum available load current under certain operating conditions is to estimate the expected converter efficiency at the maximum load current. This number can be taken out of the efficiency graphs shown in Figure 1 through Figure 4. The maximum load current can then be estimated as follows:

Equation 4. TPS61040 TPS61041 Q4_lvs413.gif

where

  • IP = Peak current as described in Peak Current Control
  • L = Selected inductor value
  • fSmax = Maximum switching frequency as calculated previously
  • η = Expected converter efficiency. Typically 70% to 85%

The maximum load current of the converter is the current at the operation point where the converter starts to enter the continuous conduction mode. Usually the converter should always operate in discontinuous conduction mode.

Last, the selected inductor should have a saturation current that meets the maximum peak current of the converter (as calculated in Peak Current Control). Use the maximum value for ILIM for this calculation.

Another important inductor parameter is the dc resistance. The lower the dc resistance, the higher the efficiency of the converter. See Table 3 and the typical applications for the inductor selection.

Table 3. Recommended Inductor for Typical LCD Bias Supply (see Figure 23)

DEVICE INDUCTOR VALUE COMPONENT SUPPLIER COMMENTS
TPS61040 10 μH Sumida CR32-100 High efficiency
10 μH Sumida CDRH3D16-100 High efficiency
10 μH Murata LQH4C100K04 High efficiency
4.7 μH Sumida CDRH3D16-4R7 Small solution size
4.7 μH Murata LQH3C4R7M24 Small solution size
TPS61041 10 μH Murata LQH3C100K24 High efficiency
Small solution size

Setting the Output Voltage

The output voltage is calculated as:

Equation 5. TPS61040 TPS61041 Q5_lvs413.gif

For battery-powered applications, a high-impedance voltage divider should be used with a typical value for R2 of ≤200 kΩ and a maximum value for R1 of 2.2 MΩ. Smaller values might be used to reduce the noise sensitivity of the feedback pin.

A feedforward capacitor across the upper feedback resistor R1 is required to provide sufficient overdrive for the error comparator. Without a feedforward capacitor, or one whose value is too small, the TPS6104x shows double pulses or a pulse burst instead of single pulses at the switch node (SW), causing higher output voltage ripple. If this higher output voltage ripple is acceptable, the feedforward capacitor can be left out.

The lower the switching frequency of the converter, the larger the feedforward capacitor value required. A good starting point is to use a 10-pF feedforward capacitor. As a first estimation, the required value for the feedforward capacitor at the operation point can also be calculated using the following formula:

Equation 6. TPS61040 TPS61041 Q6_lvs413.gif

where

  • R1 = Upper resistor of voltage divider
  • fS = Switching frequency of the converter at the nominal load current (See Inductor Selection, Maximum Load Current for calculating the switching frequency)
  • CFF = Choose a value that comes closest to the result of the calculation

The larger the feedforward capacitor the worse the line regulation of the device. Therefore, when concern for line regulation is paramount, the selected feedforward capacitor should be as small as possible. See the following section for more information about line and load regulation.

Line and Load Regulation

The line regulation of the TPS6104x depends on the voltage ripple on the feedback pin. Usually a 50 mV peak-to-peak voltage ripple on the feedback pin FB gives good results.

Some applications require a very tight line regulation and can only allow a small change in output voltage over a certain input voltage range. If no feedforward capacitor CFF is used across the upper resistor of the voltage feedback divider, the device has the best line regulation. Without the feedforward capacitor the output voltage ripple is higher because the TPS6104x shows output voltage bursts instead of single pulses on the switch pin (SW), increasing the output voltage ripple. Increasing the output capacitor value reduces the output voltage ripple.

If a larger output capacitor value is not an option, a feedforward capacitor CFF can be used as described in the previous section. The use of a feedforward capacitor increases the amount of voltage ripple present on the feedback pin (FB). The greater the voltage ripple on the feedback pin (≥50 mV), the worse the line regulation. There are two ways to improve the line regulation further:

  1. Use a smaller inductor value to increase the switching frequency which will lower the output voltage ripple, as well as the voltage ripple on the feedback pin.
  2. Add a small capacitor from the feedback pin (FB) to ground to reduce the voltage ripple on the feedback pin down to 50 mV again. As a starting point, the same capacitor value as selected for the feedforward capacitor CFF can be used.

Output Capacitor Selection

For best output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low ESR value but tantalum capacitors can be used as well, depending on the application.

Assuming the converter does not show double pulses or pulse bursts on the switch node (SW), the output voltage ripple can be calculated as:

Equation 7. TPS61040 TPS61041 Q7_lvs413.gif

where

  • IP = Peak current as described in Peak Current Control
  • L = Selected inductor value
  • Iout = Nominal load current
  • fS (Iout) = Switching frequency at the nominal load current as calculated previously
  • Vd = Rectifier diode forward voltage (typically 0.3 V)
  • Cout = Selected output capacitor
  • ESR = Output capacitor ESR value

See Table 4 and the Typical Application for choosing the output capacitor.

Table 4. Recommended Input and Output Capacitors

DEVICE CAPACITOR VOLTAGE RATING COMPONENT SUPPLIER(1) COMMENTS
TPS6104x 4.7 μF/X5R/0805 6.3 V Tayo Yuden JMK212BY475MG CIN/COUT
10 μF/X5R/0805 6.3 V Tayo Yuden JMK212BJ106MG CIN/COUT
1 μF/X7R/1206 25 V Tayo Yuden TMK316BJ105KL COUT
1 μF/X5R/1206 35 V Tayo Yuden GMK316BJ105KL COUT
4.7 μF/X5R/1210 25 V Tayo Yuden TMK325BJ475MG COUT
See Third-Party Products disclaimer.

Input Capacitor Selection

For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7-μF ceramic input capacitor is sufficient for most of the applications. For better input voltage filtering this value can be increased. See Table 4 and typical applications for input capacitor recommendations.

Diode Selection

To achieve high efficiency a Schottky diode should be used. The current rating of the diode should meet the peak current rating of the converter as it is calculated in Peak Current Control. Use the maximum value for ILIM for this calculation. See Table 5 and the typical applications for the selection of the Schottky diode.

Table 5. Recommended Schottky Diode for Typical LCD Bias Supply (see Figure 23)

DEVICE REVERSE VOLTAGE COMPONENT SUPPLIER(1) COMMENTS
TPS6104x 30 V ON Semiconductor MBR0530
20 V ON Semiconductor MBR0520
20 V ON Semiconductor MBRM120L High efficiency
30 V Toshiba CRS02
See Third-Party Products disclaimer.

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Application Curves

TPS61040 TPS61041 tc_line_lvs413.gif
Figure 13. Line Transient Response
TPS61040 TPS61041 tc_start_lvs413.gif
Figure 15. Start-Up Behavior
TPS61040 TPS61041 tc_load_lvs413.gif
Figure 14. Load Transient Response

System Examples

TPS61040 TPS61041 ai_bias_lvs413.gif Figure 16. LCD Bias Supply With Adjustable Output Voltage
TPS61040 TPS61041 ai_lcd2_lvs413.gif Figure 17. LCD Bias Supply With Load Disconnect
TPS61040 TPS61041 ai_pos_lvs413.gif Figure 18. Positive and Negative Output LCD Bias Supply
TPS61040 TPS61041 ai_stan_lvs413.gif Figure 19. Standard 3.3-V to 12-V Supply
TPS61040 TPS61041 ai_dual_lvs413.gif Figure 20. Dual Battery Cell to 5-V/50-mA Conversion
Efficiency Approximately Equals 84% at VIN = 2.4 V to Vo = 5 V/45 mA
TPS61040 TPS61041 ai_white_lvs413.gif Figure 21. White LED Supply With Adjustable Brightness Control
Using a PWM Signal on the Enable Pin, Efficiency Approximately Equals 86% at VIN = 3 V, ILED = 15 mA
TPS61040 TPS61041 ai_white2_lvs413.gif
A smaller output capacitor value for C2 causes a larger LED ripple.
Figure 22. White LED Supply With Adjustable Brightness Control
Using an Analog Signal on the Feedback Pin