SLVSAH5E December   2010  – May 2019

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Detailed Description
1. 7.1 Overview
2. 7.2 Functional Block Diagram
3. 7.3 Feature Description
4. 7.4 Device Functional Modes
8. Application and Implementation
1. 8.1 Application Information
2. 8.2 Typical Application
1. 8.2.1 Design Requirements
2. 8.2.2 Detailed Design Procedure
3. 8.2.3 Application Curves
9. Power Supply Recommendations
10. 10Layout
11. 11Device and Documentation Support
1. 11.1 Device Support
2. 11.2 Documentation Support
4. 11.4 Community Resources
6. 11.6 Electrostatic Discharge Caution
7. 11.7 Glossary
12. 12Mechanical, Packaging, and Orderable Information

• RTE|16
• RTE|16

8.2.2.8 Output-Voltage And Feedback-Resistor Selection

For the example design, the selection for R6 is 100 kΩ. Using Equation 33, calculate R7 as 80 kΩ. The nearest standard 1% resistor is 80.5 kΩ.

Equation 33.

Due to the internal design of the TPS57114-Q1 device, there is a minimum output voltage limit for any given input voltage. The output voltage can never be lower than the internal voltage reference of 0.8 V. Above 0.8 V, an output voltage limit may exist due to the minimum controllable on-time. In this case, Equation 34 gives the minimum output voltage

Equation 34.

where

• VO(min) = minimum achievable output voltage
• t(ONmin) = minimum controllable on-time (65 ns, typical; 120 ns, no load)
• f(SWmax) = maximum switching frequency, including tolerance
• VI(max) = maximum input voltage
• IO(min) = minimum load current
• rDS(on) = minimum high-side MOSFET on-resistance (15 mΩ–19 mΩ)
• R(L) = series resistance of output inductor

There is also a maximum achievable output voltage, which is limited by the minimum off-time. Equation 35 gives the maximum output voltage.

Equation 35.

where

• VO(max) = maximum achievable output voltage
• t(OFFmax) = maximum off-time (60 ns, typical)
• f(SWmax) = maximum switching frequency, including tolerance
• VI(min) = minimum input voltage
• IO(max) = maximum load current
• rDS(on) = maximum high-side MOSFET on-resistance (19 mΩ–30 mΩ)
• R(L) = series resistance of output inductor