DESCRIPCIÓN

The TPS84259 is an easy-to-use negative output voltage power module that combines a 15-W DC/DC converter with an inductor, and passives into a lowprofile QFN package. This total power solution allows as few as five external components and eliminates the loop compensation and magnetics part selection process.
The 9 × 11 × 2.8 mm QFN package is easy to solder onto a printed circuit board. Its compact design also contains fewer components and possesses excellent power dissipation capability. The TPS84259 offers the flexibility and the feature-set of a discrete design and is ideal for powering a wide range of ICs and analog circuits requiring a negative output voltage. Advanced packaging technology affords a robust and reliable power solution, compatible with standard QFN mounting and testing techniques.

 

CARACTERÍSTICAS

• Complete Integrated Power Solution Allows Small Footprint, Low-Profile Design
• WideInput-Voltage Range from 4.5 V to 40 V
• Output Adjustable from–3 V to–17 V
• Supplies up to 2-A of Output Current
• 45-V Surge Capability
• Synchronizes to an External Clock
• Adjustable Slow Start
• Programmable Undervoltage Lockout (UVLO)
• Output Overcurrent Protection
• Overtemperature Protection
• Operating Temperature Range:–40°C to +85°C
• Enhanced Thermal Performance: 14°C/W
• Meets EN55022 Class B Emissions

 

APLICACIONES

• Industrial and Motor Controls
• Automated Test Equipment
• Bipolar Amplifiers in Audio/Video
• High Density Power Systems

 

Capacitor Technologies

Electrolytic, Polymer-Electrolytic Capacitors
When using electrolytic capacitors, high-quality, computer-grade electrolytic capacitors are recommended. Polymer-electrolytic type capacitors are recommended for applications where the ambient operating temperature is less than 0°C. The Sanyo OS-CON capacitor series is suggested due to the lower ESR, higher rated surge, power dissipation, ripple current capability, and small package size. Aluminum electrolytic capacitors provide adequate decoupling over the frequency range of 2 kHz to 150 kHz, and are suitable when ambient temperatures are above 0°C.

 

Ceramic Capacitors

The performance of aluminum electrolytic capacitors is less effective than ceramic capacitors above 150 kHz. Multilayer ceramic capacitors have a low ESR and a resonant frequency higher than the bandwidth of the regulator. They can be used to reduce the reflected ripple current at the input as well as improve the transient response of the output.

 

Tantalum, Polymer-Tantalum Capacitors

Polymer-tantalum type capacitors are recommended for applications where the ambient operating temperature is less than 0°C. The Sanyo POSCAP series and Kemet T530 capacitor series are recommended rather than many other tantalum types due to their lower ESR, higher rated surge, power dissipation, ripple current capability, and small package size. Tantalum capacitors that have no stated ESR or surge current rating are not recommended for power applications.

 

Condensador de entrada

The TPS84259 requires a minimum input capacitance of 4.7 μF of ceramic type. The voltage rating of input capacitors must be greater than the maximum input voltage. The ripple current rating of the capacitor must be at least 450 mArms.

 

Power-Up Characteristics

When configured as shown in the application schematics, the TPS84259 produces a regulated output voltage following the application of a valid input voltage. During the power-up, internal soft-start circuitry slows the rate that the output voltage rises, thereby limiting the amount of in-rush current that can be drawn from the input source. The soft-start circuitry introduces a short time delay from the point that a valid input voltage is recognized.

 

Light-Load Behavior

The TPS84259 is a non-synchronous converter. One of the characteristics of non-synchronous operation is that as the output load current decreases, a point is reached where the energy delivered by a single switching pulse is more than the load can absorb. This energy causes the output voltage to rise slightly. This rise in output voltage is sensed by the feedback loop and the device responds by skipping one or more switching cycles until the output voltages falls back to the set point. At very light loads or no load, many switching cycles are skipped. The observed effect during this pulse skipping mode of operation is an increase in the peak to peak ripple voltage, and a decrease in the ripple frequency. The amount of load current when pulse skipping begins is a function of the input voltage, the output voltage, and the switching frequency.