SLVSCX0B February   2016  – April 2016 TPS62770

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1. 5.1 Output Voltage Setting Step-Down Converter
  6. 6 Specifications
    1. 6.1 ESD Ratings
    2. 6.2 Thermal Information
    3. 6.3 Electrical Characteristics
    4. 6.4 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 Step-Down Converter Device
        1. 7.3.1.1 DCS-Control
        2. 7.3.1.2 Output Voltage Selection with pins VSEL1-VSEL3
        3. 7.3.1.3 CTRL / Output Load
        4. 7.3.1.4 Output Discharge At Pins VO1 And LOAD
        5. 7.3.1.5 Undervoltage Lockout UVLO
        6. 7.3.1.6 Short Circuit Protection
      2. 7.3.2 Step-Up Converter Device
        1. 7.3.2.1 Under-Voltage Lockout
        2. 7.3.2.2 Output Disconnect
        3. 7.3.2.3 12 V Fixed Output Voltage
        4. 7.3.2.4 Mode Selection With Pin BM
        5. 7.3.2.5 Output Overvoltage Protection
        6. 7.3.2.6 Output Short Circuit Protection
        7. 7.3.2.7 PWM to Analog Converter AT PIN EN2/PWM
    4. 7.4 Device Functional Modes
      1. 7.4.1 Step-Down Converter
        1. 7.4.1.1 Enable and Shutdown
        2. 7.4.1.2 Power Save Mode Operation
        3. 7.4.1.3 PWM Mode Operation
        4. 7.4.1.4 Device Start-up and Soft Start
        5. 7.4.1.5 Automatic Transition Into 100% Mode
      2. 7.4.2 Step-Up Converter
        1. 7.4.2.1 Enable and Shutdown
        2. 7.4.2.2 Soft Start
        3. 7.4.2.3 Power Save Mode
        4. 7.4.2.4 PWM Mode
        5. 7.4.2.5 Constant-Current Step-Up Mode Operation
        6. 7.4.2.6 Constant-Voltage Step-Up Mode Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 TPS62770 Step-Down Converter + Load Switch
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Setting The Output Voltage Of The Step-Down Converter
          2. 8.2.1.2.2 Inductor Selection Step-Down Converter
          3. 8.2.1.2.3 Input and Output Capacitor Selection
        3. 8.2.1.3 Application Curves - TPS62770 Step-Down Converter + Load Switch
      2. 8.2.2 TPS62770 Step-Up Converter with Adjustable Output Voltage (9 V to 15 V)
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Programming the Output Voltage Of The Step-Up Converter
          2. 8.2.2.2.2 Inductor Selection for TPS62770 Step-Up Converter
            1. 8.2.2.2.2.1 Example Step-Up Converter with 12-V Fixed Output
        3. 8.2.2.3 Application Curves for Step-Up Converter
      3. 8.2.3 Step-Up Converter with Constant 5-V Output Voltage
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Performance Curves
      4. 8.2.4 Typical Step Up Converter with Constant Output Current
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Detailed Design Procedure
          1. 8.2.4.2.1 Setting the Output Current
          2. 8.2.4.2.2 Inductor Selection
        3. 8.2.4.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
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 TPS62770 is a tiny power solution for wearable applications including a 370 nA ultra low Iq step-down converter, a slew-rate controlled load switch and a dual-mode step-up converter. The output voltage of the step-down converter can be selected between 1.0 V and 3.0 V. The output voltage can be changed during operation. In shutdown mode, the output of the step-down converter is pulled to GND. The integrated load switch is internally connected to the output of the step-down converter and features slew rate control during turn on phase. Once turned off, its output is connected to GND. In order to achieve better supply voltage decoupling / noise reduction a capacitor can be connected on the LOAD output. The RDSON of the load switch and the connected capacitor form a RC filter.

The dual mode step-up converter can generate a constant output voltage up to 15V, e.g. for PMOLED supply, or a constant output current, e.g. for LED back light supply. The output voltage can be adjusted up to 15 V with external resistors, or set to fixed 12 V by connecting the FB pin to VIN. The device features an internal over voltage protection of 17 V in case the FB node is left open or tight to GND. It includes an internal rectifier and load disconnect function. When used as constant output current driver, the device offers a PWM to analog converter to scale down the reference voltage according to the duty cycle of the PWM signal.

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

8.2 Typical Applications

8.2.1 TPS62770 Step-Down Converter + Load Switch

TPS62770 app_TPS62770_buck_12Vfix.gif Figure 9. Simplified Schematic – TPS62770 Step-Down Converter Set to 1.8-V Output

8.2.1.1 Design Requirements

The LC output filter should meet the values shown in Table 2.

Table 2. Recommended LC Output Filter Combinations for the Step-Down Converter

INDUCTOR VALUE [µH](2) OUTPUT CAPACITOR VALUE [µF](1)
10 µF 22 µF
2.2 √(3) √
(1) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by 20% and -50%.
(2) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.
(3) This LC combination is the standard value and recommended for most applications.

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Setting The Output Voltage Of The Step-Down Converter

The output voltage is set with the VSEL1-3 pins according to Output Voltage Setting Step-Down Converter. No further external components are required.

8.2.1.2.2 Inductor Selection Step-Down Converter

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 and can be estimated according to Equation 3.

Equation 4 calculates the maximum inductor current under static load conditions. The saturation current of the inductor should be rated higher than the maximum inductor current, as calculated with Equation 4. This is recommended because during a heavy load transient the inductor current rises above the calculated value. A more conservative way is to select the inductor saturation current above the high-side MOSFET switch current limit, ILIMF.

Equation 3. TPS62770 eq4_dil_lvs941.gif
Equation 4. TPS62770 eq5_ilmax_lvs941.gif

With:

f = Switching Frequency
L = Inductor Value
ΔIL= Peak to Peak inductor ripple current
ILmax = Maximum Inductor current

In DC/DC converter applications, the efficiency is essentially affected by the inductor AC resistance (i.e. quality factor) and by the inductor DCR value. 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 (RDC) 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

8.2.1.2.3 Input and Output Capacitor Selection

Ceramic capacitors with low ESR values have the lowest output voltage ripple and are recommended. 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 light load currents, the converter operates in Power Save Mode and the output voltage ripple is dependent on the output capacitor value and the PFM peak inductor current. A 10 µF ceramic capacitor is recommended as input capacitor.

Table 3 shows a list of tested input/output capacitors.

Table 3. Components for Application Curves – TPS62770 Step-Down Converter + Load Switch

REFERENCE DESCRIPTION VALUE PACKAGE CODE / SIZE [mm x mm x mm] MANUFACTURER(1)
CIN Ceramic capacitor X5R 6.3V, GRM155R60J106ME11 10 µF 0402 / 1.0 x 0.5 x 0.5 Murata
COUT1 Ceramic capacitor X5R 6.3V, GRM155R60J106ME11 10 µF 0402 / 1.0 x 0.5 x 0.5 Murata
L1 Inductor DFE201610C 2.2 µH 2.0 x 1.6 x 1.0 Toko

8.2.1.3 Application Curves – TPS62770 Step-Down Converter + Load Switch

TPS62770 Eff_buck_VO1p0V_vs_IOUT.gif
Figure 10. Efficiency vs. IOUT, VOUT1 = 1.0 V
TPS62770 Eff_buck_VO1p8V_vs_IOUT.gif
Figure 12. Efficiency vs. IOUT, VOUT1 = 1.8 V
TPS62770 Fsw_buck_1p1VVOvs_IOUT.gif
Figure 14. FSW vs. IOUT1, VOUT1 = 1.1 V
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_IO_50uA.gif
VIN = 3.6 V IOUT = 50 µA
VOUT = 1.2 V
Figure 16. Typical Operation in Power Save Mode
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_IO_50mA.gif
VIN = 3.6 V IOUT = 50 mA
VOUT = 1.2 V
Figure 18. Typical Operation in Power Save Mode
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_LT_5mA_200mA.gif
VIN = 3.6 V IOUT = 5 mA to 200 mA
VOUT = 1.2 V 1 µs Rise/Fall Time
Figure 20. Load Transient Performance
TPS62770 SP_TO_buck_VO_1p8V_startup_after_EN.gif
VIN = 3.6 V IOUT = 0 mA
VOUT = 1.8 V
Figure 22. Startup After EN High
TPS62770 SP_TO_buck_VO_1p8V_VIN_ramp_up_down.gif
VIN = 0 V to 3.6 V in 100 µs EN = VIN
VOUT = 1.8 V IOUT = 0 mA
Figure 24. VIN Ramp Up/Down
TPS62770 SP_TO_buck_CTRL_VO1p8V_5mA_VIN_3p6V_Load_150R.gif
VIN = 3.6 V IOUT1 = 5 mA
VOUT = 1.8 V RLOAD = 150 Ω
Figure 26. Output Load Enable/Disable
TPS62770 Eff_buck_VO1p2V_vs_IOUT.gif
Figure 11. Efficiency vs. IOUT, VOUT1 = 1.2 V
TPS62770 Eff_buck_VO3p0V_vs_IOUT.gif
Figure 13. Efficiency vs. IOUT, VOUT1 = 3.0 V
TPS62770 VOU1p8V_vs_IOUT1.gif
Figure 15. VOUT1 = 1.8 V vs IOUT1
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_IO_1mA.gif
VIN = 3.6 V IOUT = 1 mA
VOUT = 1.2 V
Figure 17. Typical Operation in Power Save Mode
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_IO_200mA.gif
VIN = 3.6 V IOUT = 200 mA
VOUT = 1.2 V
Figure 19. Typical Operation in PWM Mode
TPS62770 SP_TO_buck_VO1p2V_VIN_3p6V_ac_sweep_5mA_200mA.gif
VIN = 3.6 V IOUT = 5 mA to 200 mA
VOUT = 1.2 V Sinusoidal IOUT Sweep
Figure 21. AC Load Regulation Performance
TPS62770 SP_TO_buck_VO_1p8V_startup_ramp.gif
VIN = 3.6 V IOUT = 0 mA
VOUT = 1.8 V EN Altered from Low to High
Figure 23. VOUT Ramp Up
TPS62770 SP_TO_buck_VO_1p8V_output_discharge_VO1p8V_no_load.gif
VIN = 3.6 V IOUT = 0 mA
VOUT = 1.8 V
Figure 25. Output Discharge

8.2.2 TPS62770 Step-Up Converter with Adjustable Output Voltage (9 V to 15 V)

TPS62770 TPS_Catfish_light_9Vadj.gif Figure 27. Schematic for Step-Up Converter with Adjustable Output Voltage (9V-15V)

8.2.2.1 Design Requirements

The LC output filter should meet the values shown in Table 4.

Table 4. Recommended LC Output Filter Combinations for Step-Up Converter

INDUCTOR VALUE [µH](2) VOUT IOUT OUTPUT CAPACITOR VALUE [µF](1)
10 µF 2 x 10µF
10 9 V –15 V (IOUT ≤ 30 mA) √ √
(IOUT ≤ 100 mA) √(3)
(1) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by 20% and -50%.
(2) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.
(3) This LC combination is the standard value and recommended for most applications.

8.2.2.2 Detailed Design Procedure

8.2.2.2.1 Programming the Output Voltage Of The Step-Up Converter

There are two ways to set the output voltage of the step-up converter. When the FB pin is connected to the input voltage, the output voltage is fixed to 12 V. This function reduces the external components to minimize the solution size. The second way is to use an external resistor divider to set the desired output voltage.

By selecting the external resistor divider R1 and R2, as shown in Equation 5, the output voltage is programmed to the desired value. When the output voltage is regulated, the typical voltage at the FB pin is VREF of 795 mV.

Equation 5. TPS62770 EQ1_slvscq7.gif

Where:

VOUT is the desired output voltage

VREF is the internal reference voltage at the FB pin

8.2.2.2.2 Inductor Selection for TPS62770 Step-Up Converter

The step-up converter is optimized to work with an inductor values of 10 µH. Follow Equation 6 to Equation 8 to calculate the inductor’s peak current for the application. To calculate the current in the worst case, use the minimum input voltage, maximum output voltage, and maximum load current of the application. To have enough design margin, choose the inductor value with -30% tolerance, and a low power-conversion efficiency for the calculation.

In a step-up regulator, the inductor dc current can be calculated with Equation 6.

Equation 6. TPS62770 EQ2_slvscq7.gif

Where:

VOUT = output voltage

IOUT = output current

VIN = input voltage

η = power conversion efficiency, use 80% for most applications

The inductor ripple current is calculated with the Equation 7 for an asynchronous step-up converter in continuous conduction mode (CCM).

Equation 7. TPS62770 EQ3_slvscq7.gif

Where:

ΔIL(P-P) = inductor ripple current

L = inductor value

f SW = switching frequency

VOUT = output voltage

VIN = input voltage

Therefore, the inductor peak current is calculated with Equation 8.

Equation 8. TPS62770 EQ4_slvscq7.gif

The following inductor series from different suppliers have been used:

Table 5. List Of Inductors

CONVERTER INDUCTANCE [µH] DIMENSIONS [mm3] INDUCTOR TYPE SUPPLIER(1) Output Current IOUT2
Step-up 10 2.0x1.6x1.2 VLS201610 TDK < 30mA
10 3.0 x 2.5 x 1.5 VLS302515 TDK < 100mA

8.2.2.2.2.1 Example Step-Up Converter with 12-V Fixed Output

TPS62770 app_TPS62770_step_up_12V fix.gif Figure 28. Schematic for a Step-Up Converter with Fixed 12-V Output

Table 6. Components for Application Curves for Step-Up Converter

REFERENCE DESCRIPTION VALUE PACKAGE CODE / SIZE [mm x mm x mm] MANUFACTURER(1)
CIN Ceramic capacitor X5R 6.3V, GRM155R60J106ME11 10 µF 0402 / 1.0 x 0.5 x 0.5 Murata
COUT2 Ceramic capacitor X5R 25V, GRM188R61E106MA73 2 x 10 uF 0603 / 1.6 x 0.8 x 0.8 Murata
L2 Inductor VLS302515 10 µH 3.0 x 2.5 x 1.5 TDK

8.2.2.3 Application Curves for Step-Up Converter

TPS62770 Eff_boost_VO15p0V_vs_IOUT.gif Figure 29. Efficiency vs. IOUT, VOUT = 15 V
TPS62770 VO2_12V_vs_IO2.gif
Figure 31. VOUT2 = 12 V vs IOUT2
TPS62770 SP_TO_boost_VO12V_VIN_3p6V_2mA.gif
VIN = 3.6 V IOUT2 = 2 mA
VOUT = 12 V L = 10 µH
Figure 33. Typical Operation PFM Mode
TPS62770 SP_TO_boost_VO12V_VIN_3p6V_ac_20mA.gif
VIN = 3.6 V IOUT2 = 0 mA to 20 mA
VOUT = 12 V L = 10 µH
Figure 35. AC Load Regulation Performance
TPS62770 Eff_boost_VO12p0V_vs_IOUT.gif Figure 30. Efficiency vs. IOUT, VOUT = 12 V
TPS62770 IOmax_boost_vs_VIN.gif
TA = 25°C Typical Switch Current Limit ILIM_SW
L = 10 µH IOUT2 max @ -3% VOUT Drop
COUT2 = 2x 10 µF
Figure 32. Maximum Output Current vs VIN for Typical ILIMSW
TPS62770 SP_TO_boost_VO12V_VIN_3p6V_30mA.gif
VIN = 3.6 V IOUT2 = 30 mA
VOUT = 12 V L = 10 µH
Figure 34. Typical Operation PWM Mode
TPS62770 SP_TO_boost_startup_1k_load_12V_VO.gif
VIN = 3.6 V RLOAD = 1 kΩ
VOUT = 12 V L = 10 µH
Figure 36. Startup after EN High

8.2.3 Step-Up Converter with Constant 5-V Output Voltage

TPS62770 app_boost_5V_200mA.gif Figure 37. Step-Up Converter Providing 5V VOUT2

8.2.3.1 Design Requirements

The LC output filter should meet the values shown in Table 7. For 5V Output voltage an inductor value of 4.7µH should be used for loop stability.

Table 7. Recommended LC Output Filter Combinations for Step-Up Converter

INDUCTOR VALUE [µH](2) VOUT IOUT OUTPUT CAPACITOR VALUE [µF](1)
10 µF 2 x 10µF
4.7 5 V (IOUT ≤ 200 mA) √(3)
(1) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by 20% and -50%.
(2) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.
(3) This LC combination is the standard value and recommended for most applications.

8.2.3.2 Detailed Design Procedure

For setting the output voltage, see Programming the Output Voltage Of The Step-Up Converter

Table 8. Components for Application Performance Curves

REFERENCE DESCRIPTION VALUE PACKAGE CODE / SIZE [mm x mm x mm] MANUFACTURER(1)
CIN Ceramic capacitor X5R 6.3V, GRM155R60J106ME11 10 µF 0402 / 1.0 x 0.5 x 0.5 Murata
COUT2 (2x) Ceramic capacitor X5R 6.3V, GRM188R60J106ME84 10uF 0603 / 1.6 x 0.8 x 0.8 Murata
L2 Inductor VLS302515 4.7 µH 3.0 x 2.5 x 1.5 TDK

8.2.3.3 Application Performance Curves

TPS62770 Eff_boost_VO5p0V_vs_IOUT.gif
Figure 38. Efficiency vs. IOUT, VOUT = 5.0 V
TPS62770 SP_TO_boost_VO5V_VIN_3p6V_LT_2mA_100mA_L_4p7uH_2x10uF.gif
Figure 39. Transient Response VOUT2 = 5 V

8.2.4 Typical Step Up Converter with Constant Output Current

TPS62770 app_boost_4_Leds_10mA.gif Figure 40. Step-Up Converter with Constant Output Current

8.2.4.1 Design Requirements

The step-up converter is configured to operate as a constant current driver e.g. to power 3 to 4 white LED's in a string. The maximum current through the string is set by the sense resistor RSense as shown in Figure 40 To minimize the losses in the sense resistor, the device features a 200mV internal reference, which is enabled by connecting the BM pin to high level. This section describes an application delivering 10mA through an LED string with 4 LED's which is suitable for small display used in wearable applications. See also TPS62770 Step-Up Converter with Adjustable Output Voltage (9 V to 15 V) section Design Requirements.

8.2.4.2 Detailed Design Procedure

8.2.4.2.1 Setting the Output Current

The Sense resistor to set the maximum output current can be calculated according to Equation 9 The output current IOUT2 can be reduced by applying a PWM signal at pin EN2/PWM according to Equation 10

Equation 9. TPS62770 eq_Rsense_current_mode.gif
Equation 10. TPS62770 eq_IOUT_current_mode_D.gif

Where:

RSense = sense resistor in [Ω]

IOUT2 = output current in [mA]

DPWM = Dutycycle of the PWM singal at pin EN2/PWM

8.2.4.2.2 Inductor Selection

See Inductor Selection for TPS62770 Step-Up Converter

Table 9. Components for Application Curves

REFERENCE DESCRIPTION VALUE PACKAGE CODE / SIZE [mm x mm x mm] MANUFACTURER(1)
CIN Ceramic capacitor X5R 6.3V, GRM155R60J106ME11 10 µF 0402 / 1.0 x 0.5 x 0.5 Murata
COUT2 Ceramic capacitor X5R 25V, GRM188R61E106MA73 10 uF 0603 / 1.6 x 0.8 x 0.8 Murata
L2 Inductor VLS302515 10 µH 3.0 x 2.5 x 1.5 TDK
RSense Resistor 1% 20 Ω 0402/ 1.0 x 0.5 x 0.5 Vishay
D1-D4 LED LTW-E670DS n/a Lite ON

8.2.4.3 Application Curves

TPS62770 SP_TO_boost_LED4_10mA_100perc_T150us.gif
VIN = 3.6 V RSense= 20 Ω
EN2/PWM = High 4 LEDs in Series
D = 100%, ILED = 10 mA L = 10 µH
Figure 41. Constant Current Operation with EN2/PWM = 100% D
TPS62770 SP_TO_boost_LED4_1mA_10perc_T150us.gif
VIN = 3.6 V RSense= 20 Ω
tDim_On = 15 µs, tDim_Off = 135 µs 4 LEDs in Series
D = 10%, TDIim = 140 µs, ILED = 1 mA L = 10 µH
Figure 43. Constant Current with EN2/PWM = 10% D
TPS62770 SP_TO_boost_LED4_5mA_50perc_T150us.gif
VIN = 3.6 V RSense= 20 Ω
tDim_On = 75 µs, tDim_Off = 75 µs 4 LEDs in Series
D = 50%, TDIim = 140 µs, ILED = 5 mA L = 10 µH
Figure 42. Constant Current with EN2/PWM = 50% D
TPS62770 ILED_VS_D_20kHz_3p6V_25dgc.gif
VIN = 3.6 V RSense= 20 Ω
TA = 25°C LED's in String Configuration
TDIim = 50 µs (F = 20 kHz) L = 10 µH
Figure 44. Constant Current vs D