SLVS839F July   2008  – October 2014

PRODUCTION DATA.

1. Features
2. Applications
3. Description
4. Simplified Schematic
5. Revision History
6. Pin Configuration and Functions
7. Specifications
8. Detailed Description
1. 8.1 Overview
2. 8.2 Functional Block Diagram
3. 8.3 Feature Description
4. 8.4 Device Functional Modes
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 Curves
10. 10Power Supply Recommendations
11. 11Layout
12. 12Device and Documentation Support
13. 13Mechanical, Packaging, and Orderable Information

• D|8
• DDA|8
• DDA|8

#### 9.2.2.11 Power Dissipation Estimate

The following formulas show how to estimate the device power dissipation under continuous-conduction mode (CCM) operations. These formulas should not be used if the device is working in the discontinuous-conduction mode (DCM) or pulse-skipping Eco-mode.

The device power dissipation includes:

1. Conduction loss:
2. Pcon = IOUT2 × RDS(on) × VOUT / VIN

where

• IOUT s the output current (A)
• RDS(on) is the on-resistance of the high-side MOSFET (Ω)
• VOUT is the output voltage (V)
• VIN is the input voltage (V)
3. Switching loss:
4. Psw = 0.5 × 10-9 × VIN2 × IOUT × ƒSW

where

• ƒSW is the switching frequency (Hz)
5. Gate charge loss:
6. Pgc = 22.8 × 10-9 × ƒSW
7. Quiescent current loss
8. Pq = 0.11 × 10-3 × VIN

Therefore:

Ptot = Pcon + Psw + Pgc + Pq

where

• Ptot is the total device power dissipation (W)

For given TA :

TJ = TA + Rth × Ptot

where

• TJ is the junction temperature (°C)
• TA is the ambient temperature (°C)
• Rth is the thermal resistance of the package (°C/W)

For given TJMAX = 150°C:

TAMAX = TJMAX – Rth × Ptot

where

• TJMAX is maximum junction temperature (°C)
• TAMAX is maximum ambient temperature (°C)