SLVSCX7A February   2015  – March 2015 TPS22958

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 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 (VBIAS = 5 V)
    6. 7.6  Electrical Characteristics (VBIAS = 3.3 V)
    7. 7.7  Electrical Characteristics (VBIAS = 2.5 V)
    8. 7.8  Switching Characteristics
    9. 7.9  Typical DC Characteristics
    10. 7.10 Typical AC Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 ON/OFF Control
      2. 9.3.2 Quick Output Discharge (QOD)
      3. 9.3.3 VIN and VBIAS Voltage Range
      4. 9.3.4 Adjustable Rise Time
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Input Capacitor (Optional)
      2. 10.1.2 Output Capacitor (Optional)
      3. 10.1.3 Power Supply Sequencing Without a GPIO Input
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 VIN to VOUT Voltage Drop
        2. 10.2.2.2 Inrush Current
        3. 10.2.2.3 Thermal Considerations
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Related Links
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Detailed Description

9.1 Overview

This device is a 5.5 V, 4 A / 6 A, single channel load switch with an adjustable rise time. The device contains an N-channel MOSFET controlled by an on/off GPIO-compatible input. The ON pin must be connected and cannot be left floating. The device is designed to control the turn-on rate and therefore the inrush current. By controlling the inrush current, power supply sag can be reduced during turn on. The slew rate is set by connecting a capacitor from the CT pin to GND.

The slew rate is proportional to the capacitor on the CT pin. Refer to the Adjustable Rise Time section to determine the correct CT value for a desired rise time.

The internal circuitry is powered by the VBIAS pin, which supports voltages from 2.5 to 5.5 V. This circuitry includes the charge pump, QOD, and control logic. For these internal blocks to function correctly, a voltage between 2.5 and 5.5 V must be supplied to VBIAS.

When a voltage is supplied to VBIAS and the ON pin goes low, the QOD turns on. This connects VOUT to GND through an on-chip resistor and is not a feature for the TPS22958N. The typical pull-down resistance (RPD) is 135 Ω.

9.2 Functional Block Diagram

TPS22958 TPS22958N TPS22958 functional block diagram.png

9.3 Feature Description

9.3.1 ON/OFF Control

The ON pin controls the state of the switch. Asserting ON high enables the switch. ON is active high and has a low threshold, making it capable of interfacing with low-voltage signals. The ON pin is compatible with standard GPIO logic threshold. It can be used with any microcontroller with 1.2 V or higher GPIO voltage. This pin cannot be left floating and must be tied either high or low for proper functionality.

9.3.2 Quick Output Discharge (QOD)

The TPS22958 includes a QOD feature while the TPS22958N does not. When the device is disabled, a discharge resistor is connected between VOUT and GND. This resistor has a typical value of 135 Ω and prevents the output from floating while the switch is disabled.

9.3.3 VIN and VBIAS Voltage Range

For optimal RON performance, make sure VIN ≤ VBIAS. The device will still function if VIN > VBIAS but will exhibit an RON greater than what is listed in the Electrical Characteristics table. See Figure 35 for an example of a typical device. RON increases as VIN exceeds the VBIAS voltage. For the maximum voltage ratings on the VIN and VBIAS pins, please refer to the Absolute Maximum Ratings table.

TPS22958 TPS22958N D029_TPS22958.gif
TA = 25°C IOUT = -200 mA VON = 5 V
Figure 35. RON vs VIN

9.3.4 Adjustable Rise Time

A capacitor from the CT pin to GND sets the slew rate, and it should be rated for 25 V and above. An approximate formula for the relationship between CT and slew rate with VBIAS = 5 V is:

Equation 1. SR = 0.146 × CT + 14.78

where

  • SR = slew rate (in µs/V)
  • CT = the capacitance value on the CT pin (in pF)
  • The units for the constant 14.78 is µs/V.
  • The units for the constant 0.146 is µs/(V×pF)

Rise time can be calculated by multiplying the input voltage by the slew rate. Table 1 contains rise time values measured on a typical device.

Table 1. Rise Time Table

CTx (pF) RISE TIME (µs) 10% - 90%, CL = 0.1 µF, CIN = 1 µF, RL = 10 Ω, VBIAS = 5 V
Typical values at 25°C with a 25-V X7R 10% ceramic capacitor on CT
VIN = 5 V VIN = 3.3 V VIN = 1.8 V VIN = 1.5 V VIN = 1.2 V VIN = 0.8 V VIN = 0.6 V
0 79 59 41 37 33 26 23
220 227 158 97 86 74 55 48
470 397 270 160 139 116 88 72
1000 769 522 301 258 211 153 126
2200 1659 1118 640 548 450 315 256
4700 3445 2314 1315 1128 927 656 528
10000 7310 4884 2778 2372 1950 1379 1103

9.4 Device Functional Modes

The following table lists the VOUT pin connections for a particular device as determined by the ON pin.

Table 2. VOUT Functional Table

ON (Control Input) TPS22958 TPS22958N
L GND Open
H VIN VIN