SLVS788D February   2009  – November 2016 TPS22951

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configurations and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Current Limit
      2. 8.3.2 Power Good Indication
      3. 8.3.3 EN and DET inputs
      4. 8.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
  9. 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
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8 Detailed Description

8.1 Overview

The TPS22951 smart-load switch is intended for applications where heavy capacitive loads and short circuits are likely to be encountered. This device incorporates a 1-Ω P-channel MOSFET power switch for power distribution. The switch is controlled by a logic enable (EN) input and an accessory detect (DET) pin. The switch is active when EN is high and DET is low. The switch is disabled if EN is low or DET is high. A low power state is achieved by driving EN low.

When the output load exceeds the current-limit threshold or a short is present, the device limits the output current to a safe level by increasing the on resistance of the power switch. When continuous heavy overloads and short circuits increase the power dissipation in the switch, causing the junction temperature to rise, a thermal-protection circuit shuts off the switch to prevent damage. The device recovers from a thermal shutdown once the device has cooled sufficiently, but the switch remains OFF until EN is toggled. This smart-load switch is designed to set current limit at 600 mA maximum.

8.2 Functional Block Diagram

TPS22951 ld_lvs788_PG.gif

8.3 Feature Description

8.3.1 Current Limit

The TPS22951 includes a current-limiting feature. The current limit can help protect the system from high currents in the case of large capacitive loads and short circuits. When the load current exceeds the current limit threshold, the device limits the output current by increasing the on-resistance of the switch.

8.3.2 Power Good Indication

The TPS22951 includes an open-drain Power Good indication. This signal can be used to provide an indication to another component in the system. The signal behaves according to Table 1.

To use the signal, the PG pin must be connected to a pullup resistor. The PG pin has an absolute maximum rating of 6 V and must not be pulled up to any voltage beyond 6 V. The pullp resistor must be in the range of 10 kΩ to limit the current flowing into the PG pin when the switch is on and the PG signal is low.

8.3.3 EN and DET inputs

The switch is controlled by the EN and DET pins. To enable the switch, the EN pin must be high and the DET pin must be low.

8.3.4 Thermal Shutdown

The TPS22951 includes a thermal shutdown circuit. If the device reaches the thermal shutdown threshold, the switch is automatically be disabled. The switch retrys after the device temperature has decreased and the EN pin is toggled from H to L to H.

8.4 Device Functional Modes

Table 1 lists the functional modes of the TPS22951.

Table 1. Function Table

EN DET CURRENT
LIMIT		 THERMAL
LIMIT		 POWER SWITCH
(VCC TO PWR)		 PG
(OPEN-DRAIN)
0 X Not exceeded Not exceeded OFF Z
X 1 Not exceeded Not exceeded OFF Z
1 0 Not exceeded Not exceeded ON L
1 0 Exceeded Not exceeded ON – current-limited L
X X X Exceeded (1) OFF Z
(1) To recover from a thermal event, the die temperature must first drop below the specified limit. EN must then be toggled to latch in the proper state of the flip-flop.