SLVS977B February   2010  – July 2016 TPS61325

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 Timing Requirements
    7. 7.7 Typical Characteristics
  8. Parameter Measurement Information
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  LED High-current Regulators, Unused Inputs
      2. 9.3.2  Safety Timer Accuracy
      3. 9.3.3  Current Limit Operation
      4. 9.3.4  Start-Up Sequence
      5. 9.3.5  Power Good (Flash Ready)
      6. 9.3.6  LED Temperature Monitoring
      7. 9.3.7  Hot Die Detector
      8. 9.3.8  Undervoltage Lockout
      9. 9.3.9  Storage Capacitor Active Cell Balancing
      10. 9.3.10 RED Light Privacy Indicator
      11. 9.3.11 White LED Privacy Indicator
      12. 9.3.12 Storage Capacitor, Precharge Voltage Calibration
      13. 9.3.13 Storage Capacitor, Adaptive Precharge Voltage
      14. 9.3.14 Serial Interface Description
        1. 9.3.14.1 F/S-Mode Protocol
        2. 9.3.14.2 HS-Mode Protocol
    4. 9.4 Device Functional Modes
      1. 9.4.1  Down Mode In Voltage Regulation Mode
      2. 9.4.2  Power-Save Mode Operation, Efficiency
      3. 9.4.3  Mode Of Operation: DC-Light and Flashlight
      4. 9.4.4  Flash Strobe Is Level Sensitive (STT = 0): LED Strobe Follows STRB0 and STRB1 Inputs
      5. 9.4.5  Flash Strobe Is Leading Edge Sensitive (STT = 1): One-Shot LED Strobe
      6. 9.4.6  LED Failure Modes and Overvoltage Protection
      7. 9.4.7  Hardware Voltage Mode Selection
      8. 9.4.8  Flashlight Blanking (Tx-MASK)
      9. 9.4.9  Shutdown
      10. 9.4.10 Thermal Shutdown
    5. 9.5 Programming
      1. 9.5.1 TPS6132x I2C Update Sequence
    6. 9.6 Register Maps
      1. 9.6.1  Slave Address Byte
      2. 9.6.2  Register Address Byte
      3. 9.6.3  REGISTER0 (address = 0x00)
      4. 9.6.4  REGISTER1 (address = 0x01)
      5. 9.6.5  REGISTER2 (address = 0x02)
      6. 9.6.6  REGISTER3 (address = 0x03)
      7. 9.6.7  REGISTER4 (address = 0x04)
      8. 9.6.8  REGISTER5 (address = 0x05)
      9. 9.6.9  REGISTER6 (address = 0x06)
      10. 9.6.10 REGISTER7 (address = 0x07)
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 4100-mA Two White High-Power LED Flashlight With Storage Capacitor
        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 Input Capacitor
          3. 10.2.1.2.3 Output Capacitor
          4. 10.2.1.2.4 NTC Selection
          5. 10.2.1.2.5 Checking Loop Stability
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Other Application Circuit Examples
  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 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ(パッケージ|ピン)
サーマルパッド・メカニカル・データ
発注情報

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 TPS6132x drives up to three white LEDs in parallel. The extended high-current mode (HC_SEL) allows up to 1025-mA and 2050-mA, and 1025-mA flash current out of the storage capacitor. The high-capacity storage capacitor on the output of the boost regulator provides the high-peak flash LED current, thereby reducing the peak current demand from the battery to a minimum.

In the TPS6132x device, the DC-light and flash can be controlled either by the I2C interface or by the means of hardware control signals (STRB0 and STRB1). The maximum duration of the flashlight pulse can be limited by means of an internal user programmable safety timer (STIM). The DC-light watchdog timer can be disabled by pulling high the STRB1 signal.

10.2 Typical Applications

10.2.1 4100-mA Two White High-Power LED Flashlight With Storage Capacitor

TPS61325 TPS61326 storage2_cap_lvs977.gif Figure 62. 4100-mA Two High-Power White LED Flashlight With Storage Capacitor Schematic

10.2.1.1 Design Requirements

In this application, the TPS61325 is required to drive a 4100-mA, two high-power white LED, flashlight with an input voltage range of 2.5 V to 5.5 V. This is a high-power LED application, so a storage capacitor is required to maintain sufficient headroom voltage across the LED current regulators for the entire strobe time and also minimize the power dissipation in the device.

10.2.1.2 Detailed Design Procedure

10.2.1.2.1 Inductor Selection

A boost converter requires two main passive components for storing energy during the conversion. A boost inductor and a storage capacitor at the output are required. The TPS6132x device integrates a current limit protection circuitry. The valley current of the PMOS rectifier is sensed to limit the maximum current flowing through the synchronous rectifier and the inductor. The valley peak current limit (250 mA, 1150 mA, 1600 mA) is user selectable through the I2C interface.

To optimize solution size the TPS6132x device is designed to operate with inductance values from 1.3 μH to 2.9 μH. TI recommends 2.2-µH inductance be used in typical high current white LED applications.

The highest peak current through the inductor and the power switch depends on the output load, the input and output voltages. Estimation of the maximum average inductor current and the maximum inductor peak current can be done using Equation 2 and Equation 3:

Equation 2. TPS61325 TPS61326 eq2_ll_lvs957.gif
Equation 3. TPS61325 TPS61326 eq3_llp_lvs957.gif

where

  • f = switching frequency (2 MHz)
  • L = inductance value (2.2 μH)
  • η = estimated efficiency (85%)

The losses in the inductor caused by magnetic hysteresis losses and copper losses are a major parameter for total circuit efficiency.

Table 17. List of Inductors

MANUFACTURER SERIES DIMENSIONS ILIM SETTINGS
FDK MIPST2520 2.5 mm x 2 mm x 0.8 mm (maximum) height 250 mA (typical)
MIP2520 2.5 mm x 2 mm x 1 mm (maximum) height
MIPSA2520 2.5 mm x 2 mm x 1.2 mm (maximum) height
MURATA LQM2HP-G0 2.5 mm x 2 mm x 1 mm (maximum) height
LQM2HP-GC 2.5 mm x 2 mm x 1 mm (maximum) height
TDK VLF3014AT 2.6 mm x 2.8 mm x 1.4 mm (maximum) height 1150 mA (typical)
COILCRAFT LPS3015 3 mm x 3 mm x 1.5 mm (maximum) height
MURATA LQH2HPN 2.5 mm x 2 mm x 1.2 mm (maximum) height
TOKO FDSE0312 3 mm x 3 mm x 1.2 mm (maximum) height 1600 mA (typical)
MURATA LQM32PN 3.2 mm x 2.5 mm x 1.2 mm (maximum) height

10.2.1.2.2 Input Capacitor

TI recommends low ESR ceramic capacitors for good input voltage filtering. TI recommends a 10-μF input capacitor to improve transient behavior of the regulator and EMI behavior of the total power supply circuit. The input capacitor must be placed as close as possible to the input pin of the converter.

10.2.1.2.3 Output Capacitor

The major parameter necessary to define the output capacitor is the maximum allowed output voltage ripple of the converter. This ripple is determined by two parameters of the capacitor, the capacitance and the ESR. It is possible to calculate the minimum capacitance required for the defined ripple, supposing that the ESR is zero, by using Equation 4:

Equation 4. TPS61325 TPS61326 eq4_cmin_lvs957.gif

where

  • f is the switching frequency
  • ΔV is the maximum allowed ripple

With a chosen ripple voltage of 10 mV, a minimum capacitance of 10 μF is required. The total ripple is larger due to the ESR of the output capacitor. This additional component of the ripple can be calculated using Equation 5:

Equation 5. ΔVESR = IOUT × RESR

The total ripple is the sum of the ripple caused by the capacitance and the ripple caused by the ESR of the capacitor. Additional ripple is caused by load transients. This means that the output capacitor must completely supply the load during the charging phase of the inductor. A reasonable value of the output capacitance depends on the speed of the load transients and the load current during the load change.

For the standard current white LED application (HC_SEL = 0, TPS6132x), a minimum of 3-μF effective output capacitance is usually required when operating with 2.2-μH (typical) inductors. For solution size reasons, this is usually one or more X5R or X7R ceramic capacitors.

Depending on the material, size, and therefore margin to the rated voltage of the used output capacitor, degradation on the effective capacitance can be observed. This loss of capacitance is related to the DC bias voltage applied. TI recommends checking that the selected capacitors are showing enough effective capacitance under real operating conditions.

To support high-current camera flash application (HC_SEL = 1), the converter is designed to work with a low voltage super-capacitor on the output to take advantage of the benefits they offer. A low-voltage super-capacitor in the 0.1-F to 1.5-F range, and with ESR larger than 40 mΩ, is suitable in the TPS6132x application circuit. For this device the output capacitor must be connected between the VOUT pin and a good ground connection.

10.2.1.2.4 NTC Selection

The TPS6132x requires a negative thermistor (NTC) for sensing the LED temperature. Once the temperature monitoring feature is activated, a regulated bias current, approximately 24 μA, is driven out of the TS port and produce a voltage across the thermistor.

If the temperature of the NTC-thermistor rises due to the heat dissipated by the LED, the voltage on the TS input pin decreases. When this voltage goes below the warning threshold, the LEDWARN bit in REGISTER6 is set. This flag is cleared by reading the register.

If the voltage on the TS input decreases further and falls below hot threshold, the LEDHOT bit in REGISTER6 is set and the device automatically goes into shutdown mode to avoid damaging the LED. This status is latched until the LEDHOT flag gets cleared by software.

The selection of the NTC-thermistor value strongly depends on the power dissipated by the LED and all components surrounding the temperature sensor and on the cooling capabilities of each specific application. With a 220-kΩ (at 25°C) thermistor, the valid temperature window is set from 60°C to 90°C. The temperature window can be enlarged by adding external resistors to the TS pin application circuit. To ensure proper triggering of the LEDWARN and LEDHOT flags in noisy environments, the TS signal may require additional filtering capacitance.

TPS61325 TPS61326 temp_mon2_lvs957.gif Figure 63. Temperature Monitoring Characteristic

Table 18. List of Negative Thermistor (NTC)

MANUFACTURER PART NUMBER VALUE
MURATA NCP18WM224J03RB 220 kΩ

10.2.1.2.5 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 must 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 improper board layout or inductor and capacitor combinations.

The load transient response must be tested as a next step in the evaluation of the regulation loop. VOUT can be monitored for settling time, overshoot or ringing that helps judge the converter's stability. Without any ringing, the loop usually has more than 45° of phase margin.

Because the damping factor of the circuitry is directly related to several resistive parameters (for example, MOSFET rDS(on)) that are temperature dependant, the loop stability analysis must be done over the input voltage range, output current range, and temperature range.

10.2.1.3 Application Curves

TPS61325 TPS61326 tc26_lvs977.gif Figure 64. Junction Temperature vs Port Voltage
TPS61325 TPS61326 flash_seq_lvs977.gif Figure 65. Flash Sequence (HC_SEL = 0)
TPS61325 TPS61326 tmask_op1_lvs977.gif Figure 66. Tx-Masking Operation (HC_SEL = 0)
TPS61325 TPS61326 tmask_op3_lvs977.gif Figure 68. Tx-Masking Operation (HC_SEL = 0)
TPS61325 TPS61326 pwm_ops_lvs977.gif Figure 70. PWM Operation
TPS61325 TPS61326 dn_mode_op_lvs977.gif Figure 72. Down-Mode Operation (Voltage Mode)
TPS61325 TPS61326 dc_lt_stup_lvs977.gif Figure 74. Start-Up Into DC-Light Operation
TPS61325 TPS61326 prechg_nolo_lvs977.gif Figure 76. Storage Capacitor Precharge (HC_SEL = 1)
TPS61325 TPS61326 v_stup_nolo2_lvs977.gif Figure 78. Storage Capacitor Charge-Up (HC_SEL = 1)
TPS61325 TPS61326 dc_lt_op_lvs977.gif Figure 80. DC-Light Operation (HC_SEL = 1)
TPS61325 TPS61326 fl_str70_2_lvs977.gif Figure 82. Flash Sequence (HC_SEL = 1)
TPS61325 TPS61326 fl_str35_2_lvs977.gif Figure 84. Flash Sequence (HC_SEL = 1)
TPS61325 TPS61326 hc_sel_nolo_lvs977.gif Figure 86. Shutdown (HC_SEL = 1)
TPS61325 TPS61326 tmask_op2_lvs977.gif Figure 67. Tx-Masking Operation (HC_SEL = 0)
TPS61325 TPS61326 io_dim_op_lvs977.gif Figure 69. Low-LIGHT Dimming Mode Operation
TPS61325 TPS61326 pfm_ops_lvs977.gif Figure 71. PFM Operation
TPS61325 TPS61326 pfpw_ld_tr_lvs977.gif Figure 73. Voltage Mode Load Transient Response
TPS61325 TPS61326 vmode_stup_lvs977.gif Figure 75. Start-Up Into Voltage Mode Operation
TPS61325 TPS61326 v_stup_nolo1_lvs977.gif Figure 77. Storage Capacitor Charge-Up (HC_SEL = 1)
TPS61325 TPS61326 v_setup_nolo3_lvs977.gif Figure 79. Storage Capacitor Charge-Up (HC_SEL = 1)
TPS61325 TPS61326 fl_str70_1_lvs977.gif Figure 81. Flash Sequence (HC_SEL = 1)
TPS61325 TPS61326 fl_str70_3_lvs977.gif Figure 83. Flash Sequence (HC_SEL = 1)
TPS61325 TPS61326 die_temp_lvs977.gif Figure 85. Junction Temperature Monitoring (HC_SEL = 1)

10.2.2 Other Application Circuit Examples

Figure 87 and Figure 88 show application circuit examples using the TPS61325 device. Customers must fully validate and test these circuits before implementing a design based on these examples.

TPS61325 TPS61326 privacy_lvs977.gif Figure 87. 2x 600-mA High Power White LED Solution With Privacy Indicator Schematic

In this application, TPS61325 is used to drive two 600-mA white LEDs. A storage capacitor is not necessary because the LED current can be supplied by the TPS61325 directly. The privacy indicator is turned on.

TPS61325 TPS61326 storage3_cap_lvs977.gif Figure 88. 8200-mA Four High-Power White LED Flashlight With Storage Capacitor Schematic

In this application, it is required to drive a 8200-mA, four high-power white LED, flashlight. Because it is beyond the driving capability of the TPS61325, two devices are connected in parallel to drive the LED flashlight. One works as a master with a storage capacitor, and the other works as a slave.