SLVSBB9F March   2012  – January 2017 TLV62090

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 Enable (EN)
      2. 7.3.2 Softstart (SS) and Hiccup Current Limit During Startup
      3. 7.3.3 Voltage Tracking (SS)
      4. 7.3.4 Short Circuit Protection (Hiccup-Mode)
      5. 7.3.5 Output Discharge Function
      6. 7.3.6 Power Good Output (PG)
      7. 7.3.7 Undervoltage Lockout (UVLO)
      8. 7.3.8 Thermal Shutdown
      9. 7.3.9 Charge Pump (CP, CN)
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Operation
      2. 7.4.2 Power Save Mode Operation
      3. 7.4.3 Low Dropout Operation (100% Duty Cycle)
  8. 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 Custom Design with WEBENCH® Tools
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Input and Output Capacitor Selection
        4. 8.2.2.4 Setting the Output Voltage
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guideline
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Custom Design with WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Third-Party Products Disclaimer
    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

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 TLV62090 is a 3-A high frequency synchronous step-down converter optimized for small solution size, high efficiency and suitable for battery powered applications.

8.2 Typical Application

TLV62090 typ_app_lvsbb9.gif Figure 11. TLV62090 Typical Application Circuit

8.2.1 Design Requirements

The design guideline provides a component selection to operate the device within the recommended operating conditions.

For the typical application example, the following input parameters are used. See Table 2.

Table 2. Design Parameters

DESIGN PARAMETERS EXAMPLE VALUES
Input Voltage Range 2.5 V to 5.5 V
Output Voltage 1.8 V
Transient Response ±5% VOUT
Input Voltage Ripple 400 mV
Output Voltage Ripple 30 mV
Output current rating 3 A
Operating frequency 1.4 MHz

Table 3 shows the list of components for the Application Characteristic Curves.

Table 3. List of Components

REFERENCE DESCRIPTION MANUFACTURER
TLV62090 High efficiency step-down converter Texas Instruments
L1 Inductor: 1 µH Coilcraft XFL4020-102
C1 Ceramic capacitor: 22 µF (6.3V, X5R, 0805)
C2 Ceramic capacitor: 22 µF (6.3V, X5R, 0805)
C4, C5 Ceramic capacitor, 10 nF Standard
R1, R2, R3 Resistor Standard

8.2.2 Detailed Design Procedure

8.2.2.1 Custom Design with WEBENCH® Tools

Click here to create a custom design using the TLV62090 device with the WEBENCH® Power Designer.

  1. Start by entering your VIN, VOUT, and IOUT requirements.
  2. Optimize your design for key parameters like efficiency, footprint and cost using the optimizer dial and compare this design with other possible solutions from Texas Instruments.
  3. The WEBENCH Power Designer provides you with a customized schematic along with a list of materials with real time pricing and component availability.
  4. In most cases, you will also be able to:
    • Run electrical simulations to see important waveforms and circuit performance
    • Run thermal simulations to understand the thermal performance of your board
    • Export your customized schematic and layout into popular CAD formats
    • Print PDF reports for the design, and share your design with colleagues
  5. Get more information about WEBENCH tools at www.ti.com/WEBENCH.

The first step is the selection of the output filter components. To simplify this process, Table 4 outlines possible inductor and capacitor value combinations.

Table 4. Output Filter Selection

INDUCTOR VALUE [µH](3) OUTPUT CAPACITOR VALUE [µF](2)
10 22 47 100 150
0.47 √ √ √ √
1.0 √ √(1) √ √ √
2.2 √ √ √ √ √
3.3
(1) Typical application configuration. Other check mark indicates alternative filter combinations
(2) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by +20% and –50%.
(3) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and –30%.

8.2.2.2 Inductor Selection

The inductor selection is affected by several parameters like inductor ripple current, output voltage ripple, transition point into power save mode, and efficiency. See Table 5 for typical inductors.

Table 5. Inductor Selection

INDUCTOR VALUE COMPONENT SUPPLIER SIZE (LxWxH mm) Isat/DCR (max)
0.6 µH Coilcraft XAL4012-601 4 x 4 x 2.1 7.9A/10.5 mΩ
1 µH Coilcraft XAL4020-102 4 x 4 x 2.1 6.7A/14.6 mΩ
1 µH Coilcraft XFL4020-102 4 x 4 x 2.1 4.5 A/11.9 mΩ
0.47 µH TOKO DFE252012CR47 2.5 x 2 x 1.2 3.7A/39 mΩ
1 µH TOKO DFE252012C1R0 2.5 x 2 x 1.2 3.0A/59 mΩ
0.68 µH TOKO DFE322512CR68 3.2 x 2.5 x 1.2 3.5A/35 mΩ
1 µH TOKO DFE322512C1R0 3.2 x 2.5 x 1.2 3.1A/45 mΩ

In addition, the inductor has to be rated for the appropriate saturation current and DC resistance (DCR). Equation 5 and Equation 6 calculate the maximum inductor current under static load conditions. The formula takes the converter efficiency into account. The converter efficiency can be taken from the data sheet graphs or 80% can be used as a conservative approach. The calculation must be done for the maximum input voltage where the peak switch current is highest.

Equation 5. TLV62090 eq_IL_slvsbb9.gif
Equation 6. TLV62090 eq_IL_2_slvsbb9.gif

where


ƒ = Converter switching frequency (typically 1.4 MHz)
L = Selected inductor value
η = Estimated converter efficiency (use the number from the efficiency curves or 0.80 as a conservative assumption)

Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current. A margin of about 20% should be added to cover for load transients during operation.

8.2.2.3 Input and Output Capacitor Selection

For best output and input voltage filtering, low ESR (X5R or X7R) ceramic capacitors are recommended. The input capacitor minimizes input voltage ripple, suppresses input voltage spikes and provides a stable system rail for the device. A 22-µF or larger input capacitor is recommended. The output capacitor value can range from 10 µF up to 150 µF and beyond. Load transient testing and measuring the bode plot are good ways to verify stability with larger capacitor values.

The recommended typical output capacitor value is 22 µF (nominal) and can vary over a wide range as outline in the output filter selection table. For output voltages above 1.8 V, noise can cause duty cycle jitter. This does not degrade device performance. Using an output capacitor of 2 x 22 µF (nominal) for output voltages >1.8 V avoids duty cycle jitter.

Ceramic capacitor have a DC-Bias effect, which has a strong influence on the final effective capacitance. Choose the right capacitor carefully in combination with considering its package size and voltage rating.

8.2.2.4 Setting the Output Voltage

The output voltage is set by an external resistor divider according to the following equations:

Equation 7. TLV62090 EQ2_vout_lvsaw2.gif
Equation 8. TLV62090 EQ3_R2_lvsaw2.gif
Equation 9. TLV62090 EQ4_R1_lvsaw2.gif

When sizing R2, in order to achieve low quiescent current and acceptable noise sensitivity, use a minimum of 5 µA for the feedback current IFB. Larger currents through R2 improve noise sensitivity and output voltage accuracy. A feed forward capacitor is not required for proper operation.

8.2.3 Application Curves

TLV62090 G002_SLVSAW2.png
Figure 12. Efficiency vs Load Current
TLV62090 G005_SLVSAW2.png
Figure 14. Efficiency vs Load Current
TLV62090 G012_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V/3 A f = 1.4 MHz
L = 1 µH
Figure 16. PWM Operation
TLV62090 G015_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V f = 1.4 MHz
L = 1 µH
Figure 18. Load Sweep, 0 to 1.5 A
TLV62090 plot14_lvsbb9.gif
VIN = 3.7 V VO = 1.8 V/No Load f = 1.4 MHz
L = 1 µH
Figure 20. Shutdown
TLV62090 G020_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V f = 1.4 MHz
L = 1 µH
Figure 22. Hiccup Short Circuit Protection
TLV62090 G023_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V 20 mA to 1 A
f = 1.4 MHz L = 1 µH CO = 22 µF
Figure 24. Load Transient Response
TLV62090 G003_SLVSAW2.png
Figure 13. Efficiency vs Load Current
TLV62090 G007_SLVSAW2.png
Figure 15. Output Voltage vs Load Current
TLV62090 G013_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V/100 mA f = 1.4 MHz
L = 1 µH
Figure 17. PFM Operation
TLV62090 plot13_lvsbb9.gif
VIN = 3.7 V VO = 1.8 V/600 mA
L = 1 µH CSS = 10 nF
Figure 19. Start-Up
TLV62090 G019_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V f = 1.4 MHz
L = 1 µH
Figure 21. Hiccup Short Circuit Protection
TLV62090 G022_slvsbb9.gif
VIN = 3.7 V VO = 1.8 V 0.3 A to 2.5 A
f = 1.4 MHz L = 1 µH CO = 22 µF
Figure 23. Load Transient Response