SLVSBC1D October   2013  – October 2016 TLV62565 , TLV62566

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Simplified Schematic
  5. Revision History
  6. Device Comparison Table
  7. Pin Configuration and Functions
  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. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Feature Description
      1. 9.3.1 Power Save Mode
      2. 9.3.2 Enabling/Disabling the Device
      3. 9.3.3 Soft Start
      4. 9.3.4 Switch Current Limit
      5. 9.3.5 Power Good
    4. 9.4 Device Functional Modes
      1. 9.4.1 Under Voltage Lockout
      2. 9.4.2 Thermal Shutdown
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 Output Filter Design
        2. 10.2.1.2 Inductor Selection
        3. 10.2.1.3 Input and Output Capacitor Selection
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Setting the Output Voltage
        2. 10.2.2.2 Loop Stability
      3. 10.2.3 Application Performance Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Considerations
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Related Links
    4. 13.4 Receiving Notification of Documentation Updates
    5. 13.5 Community Resources
    6. 13.6 Trademarks
    7. 13.7 Electrostatic Discharge Caution
    8. 13.8 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 TLV6256x devices are synchronous step-down converters optimized for small solution size and high efficiency. The devices integrate switches capable of delivering an output current up to 1.5 A.

10.2 Typical Application

TLV62565 2.7-V to 5.5-V input, 1.2-V output converter.

TLV62565 TLV62566 typ_app_TLV62565_1p8V.gif Figure 8. TLV62565 1.2-V Output Application

Table 1. List of Components

REFERENCE DESCRIPTION MANUFACTURER
C1 4.7 µF, Ceramic Capacitor, 6.3 V, X5R, size 0603, GRM188R60J475ME84 Murata
C2 10 µF, Ceramic Capacitor, 6.3 V, X5R, size 0603, GRM188R60J106ME84 Murata
L1 2.2 µH, Power Inductor, 2.5 A, size 4mmx4mm, LQH44PN2R2MP0 Murata
R1, R2 Chip resistor,1%,size 0603 Std.

10.2.1 Design Requirements

10.2.1.1 Output Filter Design

The inductor and output capacitor together provide a low-pass frequency filter. To simplify this process, Table 2 outlines possible inductor and capacitor value combinations.

Table 2. Matrix of Output Capacitor and Inductor Combinations

L [µH](1) COUT [µF](2) (3)
4.7 10 22 47 100
1
2.2 + (4) +(4) +
4.7
(1) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and -30%.
(2) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by +20% and -50%.
(3) For low output voltage applications (≤ 1.2 V), more output capacitance is recommended (usually ≥ 22 µF) for smaller ripple.
(4) Typical application configuration. '+' indicates recommended filter combinations.

10.2.1.2 Inductor Selection

The main parameters for inductor selection is inductor value and then saturation current of the inductor. To calculate the maximum inductor current under static load conditions, Equation 1 is given:

Equation 1. TLV62565 TLV62566 Eq_IL_peak_PWM_lvsae8.gif

where

  • IOUT,MAX is the maximum output current
  • ΔIL is the inductor current ripple
  • fSW is the switching frequency
  • L is the inductor value

It is recommended to choose a saturation current for the inductor that is approximately 20% to 30% higher than IL,MAX. In addition, DC resistance and size should also be taken into account when selecting an appropriate inductor. The recommended inductors are listed in Table 3.

Table 3. List of Recommended Inductors

INDUCTANCE
[µH]
CURRENT RATING
[mA]
DIMENSIONS
L x W x H [mm3]
DC RESISTANCE
[mΩ typ]
TYPE MANUFACTURER
2.2 2500 4 x 3.7 x 1.65 49 LQH44PN2R2MP0 Murata
2.2 3000 4 x 4 x 1.8 50 NRS4018T2R2MDGJ Taiyo Yuden

10.2.1.3 Input and Output Capacitor Selection

The input capacitor is the low impedance energy source for the converter that helps provide stable operation. The closer the input capacitor is placed to the VIN and GND pins, the lower the switch ring. A low ESR multilayer ceramic capacitor is recommended for best filtering. For most applications, 4.7-µF input capacitance is sufficient; a larger value reduces input voltage ripple.

The architecture of the TLV62565/6 allow use of tiny ceramic-type output capacitors with low equivalent series resistance (ESR). These capacitors provide low output voltage ripple and are thus recommended. To keep its resistance up to high frequencies and to achieve narrow capacitance variation with temperature, it is recommended to use X7R or X5R dielectric. The TLV62565/6 are designed to operate with an output capacitance of 10 µF to 47 µF, as outlined in Table 2.

10.2.2 Detailed Design Procedure

10.2.2.1 Setting the Output Voltage

An external resistor divider is used to set output voltage. By selecting R1 and R2, the output voltage is programmed to the desired value. When the output voltage is regulated, the typical voltage at the FB pin is VFB. Equation 2, Equation 3, and Equation 4 can be used to calculate R1 and R2.

When sizing R2, in order to achieve low current consumption 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 but increase current consumption.

Equation 2. TLV62565 TLV62566 Eq_Vo.gif
Equation 3. TLV62565 TLV62566 Eq_Vo_2.gif
Equation 4. TLV62565 TLV62566 Eq_Vo_3.gif

Due to the maximum duty cycle limit, the output voltage is out of regulation if the input voltage is too low. For proper regulation, VOUT should be set below VIN_MIN as shown in Equation 5.

Equation 5. TLV62565 TLV62566 eq_Vout_Max_SLVSBC1.gif

where

  • VIN_MIN, the minimum value of the input voltage;

10.2.2.2 Loop Stability

The first step of circuit and stability evaluation is to look from a steady-state perspective at the following signals:

  • Switching node, SW
  • Inductor current, IL
  • Output ripple voltage, VOUT(AC)

These are the basic signals that need to be measured when evaluating a switching converter. When the switching waveform shows large duty cycle jitter or the output voltage or inductor current shows oscillations, the regulation loop may be unstable. This is often a result of board layout and/or L-C combination. Applications with the recommended L-C combinations in Table 2 are designed for good loop stability as well as fast load transient response.

As a next step in the evaluation of the regulation loop, the load transient response is illustrated. The TLV62565/6 use a constant on time with valley current mode control, so the on time of the high-side MOSFET is relatively consistent from cycle to cycle when a load transient occurs. Whereas the off time adjusts dynamically in accordance with the instantaneous load change and brings VOUT back to the regulated value.

During recovery time, VOUT can be monitored for settling time, overshoot, or ringing which helps judge the stability of the converter. Without any ringing, the loop usually has more than 45° of phase margin.

10.2.3 Application Performance Curves

TLV62565 TLV62566 C001_eff_SLVSBC1.png
Figure 9. Efficiency vs Load Current
TLV62565 TLV62566 C003_eff_SLVSBC1.png
Figure 11. Efficiency vs Load Current
TLV62565 TLV62566 C004_Vout_SLVSBC1.png
Figure 13. Output Voltage vs Load Current
TLV62565 TLV62566 G002_PFM_SLVSBC1.gif
Figure 15. Typical Application (PFM Mode)
TLV62565 TLV62566 G007_Loadtran1_SLVSBC1.gif
Figure 17. Load Transient
TLV62565 TLV62566 G004_ENStartup_SLVSBC1.gif
IOUT = 1.5 A
Figure 19. Start Up
TLV62565 TLV62566 G006_Short_SLVSBC1.gif
No load to short circuit
Figure 21. Short Circuit Protection
TLV62565 TLV62566 C002_eff_SLVSBC1.png
Figure 10. Efficiency vs Load Current
TLV62565 TLV62566 C011_Vout_SLVSBC1.png
Figure 12. Output Voltage vs Input Voltage
TLV62565 TLV62566 G001_PWM_SLVSBC1.gif
IOUT = 1.5 A
Figure 14. Typical Application (PWM Mode)
TLV62565 TLV62566 G003_PFM_SLVSBC1.gif
Figure 16. Typical Application (PFM Mode)
TLV62565 TLV62566 G008_Loadtran2_SLVSBC1.gif
Figure 18. Load Transient
TLV62565 TLV62566 G005_PGStartup_SLVSBC1.gif
Figure 20. Start Up (Power Good)