SLVS848D July   2009  – October 2015 TPS62620 , TPS62621 , TPS62622 , TPS62623 , TPS62624 , TPS62625

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Mode Selection
      2. 8.3.2 Enable
      3. 8.3.3 Undervoltage Lockout
      4. 8.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Soft Start
      2. 8.4.2 Switching Frequency
      3. 8.4.3 Power-Save Mode
      4. 8.4.4 Output Capacitor Discharge (TPS62624 Only)
      5. 8.4.5 Short-Circuit Protection
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Inductor Selection
        2. 9.2.2.2 Output Capacitor Selection
        3. 9.2.2.3 Input Capacitor Selection
        4. 9.2.2.4 Checking Loop Stability
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Information
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information
    1. 13.1 Package Summary
    2. 13.2 Chip Scale Package Dimensions

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発注情報

9 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.

9.1 Application Information

The TPS6262x device family provides high-frequency synchronous step-down DC/DC converters optimized for battery-powered portable applications. Intended for low-power applications, the TPS6262x devices support up to 600 mA load current, and allow the use of low cost chip inductor and capacitors.

9.2 Typical Application

TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 pmi_lvs848.gif Figure 5. TPS6262x Typical Application Schematic

9.2.1 Design Requirements

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

Table 1 shows the list of components for the Application Curves.

Table 1. List of Components

REFERENCE DESCRIPTION MANUFACTURER
L 1 μH MURATA LQM21PN1R0NGR
CIN 2.2μF, 6.3V, 0402, X5R MURATA GRM155R60J225ME15
COUT 4.7μF, 6.3V, 0402, X5R MURATA GRM155R60J475M

9.2.2 Detailed Design Procedure

9.2.2.1 Inductor Selection

The TPS6262x device family of step-down converters have been optimized to operate with an effective inductance value in the range of 0.3 μH to 1.3 μH and with output capacitors in the range of 4.7 μF to 10 μF. The internal compensation is optimized to operate with an output filter of L = 0.47 μH and COUT = 4.7 μF. Larger or smaller inductor values can be used to optimize the performance of the device for specific operation conditions. For more details, see section Checking Loop Stability.

The inductor value affects its peak-to-peak ripple current, the PWM-to-PFM transition point, the output voltage ripple and the efficiency. The selected inductor has to be rated for its DC resistance and saturation current. The inductor ripple current (ΔIL) decreases with higher inductance and increases with higher VIN or VOUT.

Equation 1. TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eq1_app_slvs848.gif

where

  • fSW = Switching frequency (6 MHz typical)
  • L = Inductor value
  • ΔIL = Peak-to-peak inductor ripple current
Equation 2. TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eq2_app_slvs848.gif

where

  • ΔIL = Peak-to-peak inductor ripple current
  • IL(MAX) = Maximum inductor current

In high-frequency converter applications, the efficiency is essentially affected by the inductor AC resistance (i.e. quality factor) and to a smaller extent by the inductor DCR value. To achieve high efficiency operation, care should be taken in selecting inductors featuring a quality factor above 25 at the switching frequency. Increasing the inductor value produces lower RMS currents, but degrades transient response. For a given physical inductor size, increased inductance usually results in an inductor with lower saturation current.

The total losses of the coil consist of both the losses in the DC resistance (R(DC)) and the following frequency-dependent components:

  • The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
  • Additional losses in the conductor from the skin effect (current displacement at high frequencies)
  • Magnetic field losses of the neighboring windings (proximity effect)
  • Radiation losses

The following inductor series from different suppliers have been used with the TPS6262x converters.

Table 2. List Of Inductors(1)

MANUFACTURER SERIES DIMENSIONS
MURATA LQM21PN1R0NGR 2.0 x 1.2 x 1.0 max. height
LQM21PNR54MG0 2.0 x 1.2 x 1.0 max. height
LQM21PNR47MC0 2.0 x 1.2 x 0.55 max. height
LQM21PN1R0MC0 2.0 x 1.2 x 0.55 max. height
LQM21PN1R5MC0 2.0 x 1.2 x 0.55 max. height
HITACHI METALS HSLI-201210AG-R47 2.0 x 1.2 x 1.0 max. height
HSLI-201210SW-R85 2.0 x 1.2 x 1.0 max. height
JSLI-201610AG-R70 2.0 x 1.6 x 1.0 max. height
TOKO MDT2012-CX1R0A 2.0 x 1.2 x 1.0 max. height
FDK MIPS2012D1R0-X2 2.0 x 1.2 x 1.0 max. height
TAIYO YUDEN NM2012NR82 2.0 x 1.2 x 1.0 max. height
NM20121NR0 2.0 x 1.2 x 1.0 max. height
(1) See the Third-Party Products disclaimer.

9.2.2.2 Output Capacitor Selection

The advanced fast-response voltage mode control scheme of the TPS6262x converters allows the use of tiny ceramic capacitors. Ceramic capacitors with low ESR values have the lowest output voltage ripple and are recommended. For best performance, the device should be operated with a minimum effective output capacitance of 1.6 μF. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequencies.

At nominal load current, the device operates in PWM mode and the overall output voltage ripple is the sum of the voltage step caused by the output capacitor ESL and the ripple current flowing through the output capacitor impedance.

At light loads, the output capacitor limits the output ripple voltage and provides holdup during large load transitions. A 4.7 μF capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions. The typical output voltage ripple is 1% of the nominal output voltage VOUT.

The output voltage ripple during PFM mode operation can be kept very small. The PFM pulse is time controlled, which allows to modify the charge transferred to the output capacitor by the value of the inductor. The resulting PFM output voltage ripple and PFM frequency depend in first order on the size of the output capacitor and the inductor value. The PFM frequency decreases with smaller inductor values and increases with larger ones. Increasing the output capacitor value and the effective inductance will minimize the output ripple voltage.

9.2.2.3 Input Capacitor Selection

Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is required to prevent large voltage transients that can cause misbehavior of the device or interferences with other circuits in the system. For most applications, a 2.2-μF capacitor is sufficient.

Take care when using only ceramic input capacitors. When a ceramic capacitor is used at the input and the power is being supplied through long wires, such as from a wall adapter, a load step at the output can induce ringing at the VIN pin. This ringing can couple to the output and be mistaken as loop instability or could even damage the part. Additional "bulk" capacitance (electrolytic or tantalum) should in this circumstance be placed between CIN and the power source lead to reduce ringing than can occur between the inductance of the power source leads and CIN.

9.2.2.4 Checking 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.

As a next step in the evaluation of the regulation loop, the load transient response is tested. The time between the application of the load transient and the turn on of the P-channel MOSFET, the output capacitor must supply all of the current required by the load. VOUT immediately shifts by an amount equal to ΔI(LOAD)  x  ESR, where ESR is the effective series resistance of COUT. ΔI(LOAD) begins to charge or discharge COUT generating a feedback error signal used by the regulator to return VOUT to its steady-state value. The results are most easily interpreted when the device operates in PWM mode.

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

Because the damping factor of the circuitry is directly related to several resistive parameters (e.g., MOSFET RDS(on)) that are temperature dependant, the loop stability analysis has to be done over the input voltage range, load current range, and temperature range.

9.2.3 Application Curves

TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eff3_io_lvs848.gif
VOUT = 1.82 V
Figure 6. Efficiency vs Load Current, VOUT = 1.82 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eff4_io_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V PFM/PWM Operation
Figure 8. Efficiency vs Load Current, VOUT = 1.82 V, PWM/PFM Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eff_vi_lvs848.gif
VOUT = 1.82 V PFM/PWM Operation
Figure 10. Efficiency vs Input Voltage, VOUT = 1.82 V, PWM/PFM Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 vo_io_lvs848.gif
VOUT = 1.2 V
Figure 12. Peak-To-Peak Output Ripple Voltage vs Load Current, VOUT = 1.2 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 line3_trns_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 14. Combined Line/Load Transient Response,
VOUT = 1.82 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load2_tr_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 16. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load_pfm_lvs848.gif
VOUT = 1.82 V VIN = 4.8 V MODE = Low
Figure 18. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 4.8 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load_pwm2_lvs848.gif
VOUT = 1.82 V VIN = 2.7 V MODE = Low
Figure 20. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 2.7 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 trans_res_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V MODE = Low
Figure 22. Load Transient Response in PFM/PWM Operation, VOUT = 1.2 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 trans3_res_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V MODE = Low
Figure 24. Load Transient Response in PFM/PWM Operation, VOUT = 1.2 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 ac2_load_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V MODE = Low
Figure 26. AC Load Transient Response, VOUT = 1.2 V,
VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 vob_io_lvs848.gif
VOUT = 1.2 V PFM/PWM Operation
Figure 28. DC Output Voltage vs Load Current,
VOUT = 1.2 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 io3_vi3_lvs848.gif
VOUT = 1.2 V Mode Change
Figure 30. PFM/PWM Boundaries, VOUT = 1.2 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 pwm_op_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 100 mA MODE = High
Figure 32. PWM Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 mode_chg_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 40 mA
Figure 34. Mode Change Response
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 ovr_cur_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 40 mA
MODE = Low
Figure 36. Over-Current Fault Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 shutdown_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V IOUT = 0 mA
TPS62624 MODE = Low
Figure 38. Shutdown
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eff_io_lvs848.gif
VOUT = 1.2 V
Figure 7. Efficiency vs Load Current, VOUT = 1.2 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 eff4b_io_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V PFM/PWM Operation
Figure 9. Efficiency vs Load Current, VOUT = 1.2 V, PWM/PFM Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 effb_vi_lvs848.gif
VOUT = 1.82 V
Figure 11. Peak-To-Peak Output Ripple Voltage vs Load Current, VOUT = 1.82 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 line2_trns_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 13. Combined Line/Load Transient Response, VOUT = 1.82 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load_tr_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 15. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load3_tr_lvs848.gif
VOUT = 1.82 V VIN = 2.7 V MODE = Low
Figure 17. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 2.7 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load_pwm_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 19. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 load_pfm2_lvs848.gif
VOUT = 1.82 V VIN = 4.8 V MODE = Low
Figure 21. Load Transient Response in PFM/PWM Operation, VOUT = 1.82 V, VIN = 4.8 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 trans2_res_lvs848.gif
VOUT = 1.2 V VIN = 3.6 V MODE = Low
Figure 23. Load Transient Response in PFM/PWM Operation, VOUT = 1.2 V, VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 ac_load_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V MODE = Low
Figure 25. AC Load Transient Response, VOUT = 1.82 V,
VIN = 3.6 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 voc_io_lvs848.gif
VOUT = 1.82 V PFM/PWM Operation
Figure 27. DC Output Voltage vs Load Current,
VOUT = 1.82 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 io2_vi2_lvs848.gif
VOUT = 1.82 V Mode Change
Figure 29. PFM/PWM Boundaries, VOUT = 1.82 V
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 fs_vi_lvs848.gif
VOUT = 1.82 V
Figure 31. PWM Switching Frequency vs Input Voltage
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 pwsvr_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 40 mA
MODE = Low
Figure 33. Power-Save Mode Operation
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 mode2_chg_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 40 mA
Figure 35. Mode Change Response
TPS62620 TPS62621 TPS62622 TPS62623 TPS62624 TPS62625 start_up_lvs848.gif
VOUT = 1.82 V VIN = 3.6 V IOUT = 0 mA
TPS62620 MODE = Low
Figure 37. Start-Up