SNOSAV4C April   2008  – August 2026 LM7332

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Thermal Information
    4. 5.4 Recommended Operating Conditions
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
    7. 5.7 Old vs. New Die Comparison
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Device Functional Modes
      1. 6.3.1 Driving Capacitive Loads
    4. 6.4 Electrical Overstress
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
      3. 7.4.3 Output Short Circuit Current and Dissipation Issues
  9. 8 Device and Documentation Support
    1. 8.1 Support Resources
    2. 8.2 Trademarks
    3. 8.3 Electrostatic Discharge Caution
    4. 8.4 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.4.3 Output Short Circuit Current and Dissipation Issues

The LM7332 output stage is designed for maximum output current capability. Even though momentary output shorts to ground and either supply can be tolerated at all operating voltages, longer-lasting short conditions can cause the junction temperature to rise beyond the absolute maximum rating of the device, especially at higher supply voltage conditions.

With the operational amplifier tied to a load, the device power dissipation consists of the quiescent power due to the supply current flow into the device, in addition to power dissipation due to the load current. The load portion of the power can include an average value (due to a DC load current) and an AC component. DC load current flows if there is an output voltage offset, or the output AC average current is non-zero, or if the operational amplifier operates in a single-supply application where the output is maintained somewhere in the range of linear operation.

Therefore,

Equation 5. P T O T A L = P Q + P D C + P A C

The operational amplifier quiescent power dissipation is calculated by Equation 6:

Equation 6. P Q = I S × V S

where

  • IS: Supply Current
  • VS: Total Supply Voltage (V+ − V−)

The DC load power is calculated by Equation 7:

Equation 7. P D C = I O × V r - V O

where

  • VO: Average Output Voltage
  • Vr: V+ for sourcing and V− for sinking current

The AC load power is calculated as PAC = the value shown in Table 7-1.

Table 7-1 shows the maximum AC component of the load power dissipated by the operational amplifier for standard sinusoidal, triangular, and square waveforms:

Table 7-1 Normalized AC Power Dissipated in the Output Stage for Standard Waveforms
PAC (W.Ω/V2)
SINUSOIDALTRIANGULARSQUARE
50.7 × 10−346.9 × 10−362.5 × 10−3

The table entries are normalized to VS2/RL. To figure out the AC load current component of power dissipation, simply multiply the table entry corresponding to the output waveform by the factor VS2/RL. For example, with ±12V supplies, a 600Ω load, and triangular waveform power dissipation in the output stage is calculated as:

Equation 8. P A C = 46.9 × 10 - 3 × 24 2 ∕   600 =   45.0 m W

The maximum power dissipation allowed at a certain temperature is a function of maximum die junction temperature (TJ(MAX)) allowed, ambient temperature TA, and package thermal resistance from junction to ambient, RθJA.

Equation 9. P D M A X = T J M A X - T A R θ J A

For the LM7332, the maximum junction temperature allowed is 150°C at which no power dissipation is allowed. The power capability at 25°C is given by:

For VSSOP package:

Equation 10. P D M A X = 150 ℃ -   25 ℃ 169.6 ℃ = 0.737 W

For SOIC package:

Equation 11. P D M A X = 150 ℃ -   25 ℃ 124 ℃ = 1.008 W

Similarly, the power capability at 125°C is given by:

For VSSOP package:

Equation 12. P D M A X = 150 ℃ -   25 ℃ 169.6 ℃ = 0.147 W

For SOIC package:

Equation 13. P D M A X = 150 ℃ -   25 ℃ 124 ℃ = 0.202 W

When the device works in the operating area where PTOTAL is less than PD(MAX), the device junction temperature remains below 150°C. When high power is required and ambient temperature cannot be reduced, providing air flow is an effective approach to reduce thermal resistance therefore to improve power capability.