SLVS432F September   2002  – June 2015 TPS62050 , TPS62051 , TPS62052 , TPS62054 , TPS62056

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 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. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Enable and Overtemperature Protection
      2. 9.3.2 Low-Battery Detector (Standard Version)
      3. 9.3.3 ENABLE / Low-Battery Detector (Enhanced Version) TPS62051 Only
      4. 9.3.4 Undervoltage Lockout
      5. 9.3.5 Power Good Comparator
      6. 9.3.6 Synchronization
    4. 9.4 Device Functional Modes
      1. 9.4.1 Soft-Start
      2. 9.4.2 Constant Frequency Mode Operation (SYNC = HIGH)
      3. 9.4.3 Power-Save Mode Operation (SYNC = LOW)
      4. 9.4.4 100% Duty Cycle Low Dropout Operation
      5. 9.4.5 No Load Operation
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Standard Circuit for Adjustable Version
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Inductor Selection
          2. 10.2.1.2.2 Output Capacitor Selection
          3. 10.2.1.2.3 Input Capacitor Selection
          4. 10.2.1.2.4 Feedforward Capacitor
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Standard Circuit for Fixed Voltage Version
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
        3. 10.2.2.3 Application Curves
    3. 10.3 System Examples
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Related Links
    3. 13.3 Community Resource
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 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 TPS6205x family of devices are high-efficiency synchronous step-down DC-DC converters ideally suited for systems powered from a 1-cell or 2-cell Li-Ion battery or from a 3-cell to 5-cell NiCd, NiMH, or alkaline battery.

10.2 Typical Applications

10.2.1 Standard Circuit for Adjustable Version

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 ai_stand_adj_lvs432.gifFigure 6. Standard Circuit for Adjustable Version

10.2.1.1 Design Requirements

The design guidelines provide a component selection to operate the adjustable device within the Recommended Operating Conditions.

Table 1. Bill of Materials for Adjustable Version

REFERENCE PART NUMBER VALUE MANUFACTURER
Ci C3216X5R1A106M 10 µF TDK
Co JMK316BJ226ML 22 µF Taiyo Yuden
L1 WE PD 74477710 10 µH Wurth
IC1 TPS62050 - Texas Instruments
R1 generic metal film resistor; tolerance 1% 820 kΩ (depending on desired output voltage) —
R2 generic metal film resistor; tolerance 1% 91 kΩ (depending on desired output voltage) —
R3, R4 generic metal film resistor; tolerance 1% 1 MΩ —
R5 generic metal film resistor; tolerance 1% 130 kΩ —
R6 generic metal film resistor; tolerance 1% 100 kΩ —
C(ff) generic ceramic capacitor; COG 6.8 pF —

10.2.1.2 Detailed Design Procedure

All graphs have been generated using the circuit as shown unless otherwise noted. For output voltages other than 5 V, the fixed-voltage versions were used. The resistors R1, R2, and the feed forward capacitor (Cff) are removed and the feedback pin is directly connected to the output.

Equation 2. TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 Q_VO_VFB_lvs432.gif

Table 2. Values for Resistor Combinations and Feedback Capacitors

NOMINAL OUTPUT VOLTAGE EQUATION POSSIBLE RESISTOR COMBINATION TYPICAL FEEDBACK CAPACITOR
0.7 V R1 = 0.4 × R2 R1 = 270 k, R2 = 680 k C(ff) = 22 pF
1.2 V R1 = 1.4 × R2 R1 = 510 k, R2 = 360 k (1.21 V) C(ff) = 6.8 pF
1.5 V R1 = 2 × R2 R1 = 300 k, R2 = 150 k (1.5 V) C(ff) = 6.8 pF
1.8 V R1 = 2.6 × R2 R1 = 390 k, R2 = 150 k (1.80 V) C(ff) = 6.8 pF
2.5 V R1 = 4 × R2 R1 = 680 k, R2 = 169 k (2.51 V) C(ff) = 6.8 pF
3.3 V R1 = 5.6 × R2 R1 = 560 k, R2 = 100 k (3.3 V) C(ff) = 6.8 pF
5 V R1 = 9 × R2 R1 = 820 k, R2 = 91 k (5 V) C(ff) = 6.8 pF

10.2.1.2.1 Inductor Selection

A 10-µH minimum inductor must be used with the TPS6205x family of devices. Values larger than 22 µH or smaller than 10 µH may cause stability problems due to the internal compensation of the regulator. After choosing the inductor value of typically 10 µH, two additional inductor parameters must be considered: the current rating of the inductor and the DC resistance. The DC resistance of the inductance directly influences the efficiency of the converter. Therefore, an inductor with lowest DC resistance must be selected for highest efficiency. To avoid saturation of the inductor, the inductor must be rated at least for the maximum output current plus half the inductor ripple current which is calculated using Equation 3.

Equation 3. TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 Q_IL_VO_lvs432.gif

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 the TPS6205x device, which is 1.4 A maximum. See Table 3 for inductors that have been tested for operation with the TPS6205x devices.

Table 3. Inductors

MANUFACTURER TYPE INDUCTANCE DC RESISTANCE SATURATION CURRENT
TDK SLF7032T-100M1R4SLF7032T-220M96SLF7045T-100M1R3SLF7045T-100MR90 10 µH ±20%
22 µH ±20%
10 µH ±20%
22 µH ±20%		 53 mΩ ±20%
110 mΩ ±20%
36 mΩ ±20%
61 mΩ ±20%		 1.4 A
0.96 A
1.3 A
0.9 A
Sumida CDR74B 10 µH 70 mΩ 1.65 A
CDR74B 22 µH 130 mΩ 1.12 A
CDH74 10 µH 49 mΩ 1.8 A
CDH74 22 µH 110 mΩ 1.23 A
CDR63B 10 µH 140 mΩ 1 A
CDRH4D28 10 µH 128 mΩ 1 A
CDRH5D28 10 µH 48 mΩ 1.3 A
CDRH5D18 10 µH 92 mΩ 1.2 A
Coilcraft DT3316P-153 15 µH 60 mΩ 1.8 A
DT3316P-223 22 µH 84 mΩ 1.5 A
Wuerth WE-PD 744 778 10 10 µH 72 mΩ 1.68 A
WE-PD 744 777 10 10 µH 49 mΩ 1.84 A
WE-PD 744 778 122 22 µH 190 mΩ 1.07A
WE-PD 744 777 122 22 µH 110 mΩ 1.23 A

10.2.1.2.2 Output Capacitor Selection

The output capacitor must have a minimum value of 22 µF. For best performance, a low ESR ceramic output capacitor is needed.

For completeness, use Equation 4 to calculate the RMS ripple current.

Equation 4. TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 Q_IRMS_VO_lvs432.gif

The overall output ripple voltage is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charge and discharging the output capacitor, as shown in Equation 5.

Equation 5. TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 Q_VO_VO_lvs432.gif

The highest output voltage ripple occurs at the highest input voltage VI.

10.2.1.2.3 Input Capacitor Selection

Because the buck converter has a pulsating input current, a low ESR input capacitor is required for best input voltage filtering and minimizing the interference with other circuits caused by high input voltage spikes. The input capacitor must have a minimum value of 10 µF and can be increased without any limit for better input voltage filtering. The input capacitor must be rated for the maximum input ripple current calculated as:

Equation 6. TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 Q_IRMS_IO_lvs432.gif

The worst-case RMS ripple current occurs at D = 0.5 and is calculated as: IRMS = IO/2. Ceramic capacitors have a good performance because of their low ESR value and they are less sensitive to voltage transients compared to tantalum capacitors. Place the input capacitor as close as possible to the input pin of the IC for best performance.

Table 4. Capacitors

MANUFACTURER PART NUMBER SIZE VOLTAGE CAPACITANCE TYPE
Taiyo Yuden JMK212BJ106MG 0805 6.3 V 10 µF Ceramic
JMK316BJ106ML 1206 6.3 V 10 µF Ceramic
JMK316BJ226ML 1206 6.3 V 22 µF Ceramic
LMK316BJ475ML 1206 10 V 4.7 µF(1) Ceramic
EMK316BJ475ML 1206 16 V 4.7 µF(1) Ceramic
EMK325BJ106KN-T 1210 16 V 10 µF Ceramic
Kemet C1206C106M9PAC 1206 6.3 V 10 µF Ceramic
TDK C2012X5R0J106M 0805 6.3 V 10 µF Ceramic
C3216X5R0J226M 1206 6.3 V 22 µF Ceramic
C3216X5R1A106M 1206 10 V 10 µF Ceramic
(1) Connect two in parallel.

10.2.1.2.4 Feedforward Capacitor

The feedforward capacitor (C(ff) shown in Figure 5) improves the performance in SKIP mode. The comparator is faster; therefore, there is less voltage ripple at the output in SKIP mode. Use the values listed in Table 2. Larger values decrease stability in fixed frequency PWM mode. If the TPS6205x devices are only operated in fixed frequency PWM mode, the feedforward capacitor is not needed.

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 ai_PSM_lvs432.gifFigure 7. Power-Save Mode Output Voltage Thresholds

The converter enters the fixed frequency PWM mode again as soon as the output voltage falls below the comparator low 2 threshold set to 1.6% below VO, nominal.

10.2.1.3 Application Curves

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff50l_il_lvs432.gifFigure 8. TPS62050 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff52l_il_lvs432.gifFigure 10. TPS62052 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff56h_il_lvs432.gifFigure 12. TPS62056 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 OVR_v_skip_lvs432.gifFigure 14. Output Voltage Ripple in Skip Mode
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 line_TR_lvs432.gifFigure 16. Line Transient Response in PWM Mode
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 VS_and_IL_lvs432.gifFigure 18. V(SWITCH) and IL
(Inductor Current) in Skip Mode
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff56l_il_lvs432.gifFigure 9. TPS62056 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff50h_il_lvs432.gifFigure 11. TPS62050 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff52h_il_lvs432.gifFigure 13. TPS62052 Efficiency vs Load Current
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 OVR_PWM_lvs432.gifFigure 15. Output Voltage Ripple in PWM Mode
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 load_TR_lvs432.gifFigure 17. Load Transient Response
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 startup_lvs432.gifFigure 19. Start-up Timing

10.2.2 Standard Circuit for Fixed Voltage Version

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 ai_fixed_cir_lvs432.gifFigure 20. Standard Circuit for Fixed Voltage Version

10.2.2.1 Design Requirements

The design guidelines provide a component selection to operate the device within the Recommended Operating Conditions.

Table 5. Bill of Materials for Fixed Voltage Versions

REFERENCE PART NUMBER VALUE MANUFACTURER
Ci C3216X5R1A106M 10 µF TDK
Co JMK316BJ226ML 22 µF Taiyo Yuden
L1 WE PD 74477710 10 µH Wurth
IC1 TPS62054 — Texas Instruments
R3, R4 generic metal film resistor; tolerance 1% 1 MΩ —
R5 generic metal film resistor; tolerance 1% 130 kΩ —
R6 generic metal film resistor; tolerance 1% 100 kΩ —

10.2.2.2 Detailed Design Procedure

Connect the feedback pin (FB) to the pad of the output capacitor. The pullup resistors for pins PG and LBO are typically chosen as 100 kΩ each. The input capacitor must be placed as close to the VIN pin as possible.

10.2.2.3 Application Curves

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff54l_il_lvs432.gifFigure 21. TPS62054 Efficiency vs Load Current in PFM Mode
TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 eff54h_il__lvs432.gifFigure 22. TPS62054 Efficiency vs Load Current in PWM Mode

10.3 System Examples

The TPS62050 device is used to generate an output voltage of 0.7 V. With such low output voltages, the inductor discharges very slowly. This leads to a high-output voltage ripple in power-save mode (SYNC = GND). Therefore, TI recommends using a larger output capacitor to keep the output ripple low. With an output capacitor of 47 µF, the output voltage ripple is less than 40 mVPP.

TPS62050 TPS62051 TPS62052 TPS62054 TPS62056 ai_converter_lvs432.gifFigure 23. Converter for 0.7-V Output Voltage