TPS61254YFFT

TPS61254YFFT Application Field and Working Principle

TPS61254YFFT is a monolithic synchronous step up converter with all the features needed for a current-limited high efficiency application. It belongs to a category of PMIC (Power Management ICs) voltage regulators called DC DC Switching Regulators.

Features

• Available in 1.5V to 6V application voltage range
• Maximum input voltage of 16V
• Current-mode control topology
• High accuracy constant frequency current-mode
• 50mV input voltage transition (for VIN ≥ 2V)
• Two power-saving stages to reduce quiescent current
• Build-in Power MOSFET
• Output voltage accuracy ±2%
• Integrated soft start
• Thermal shutdown protection
• Output disable

Applications

• Cellular phones
• Handsets
• CDMA/WCDMA/TDMA/GSM
• Wireless modems
• Personal digital assistant (PDAs)
• Portable Stereo player
• Portable DVD players
• Portable digital cameras
• Portable gaming consoles

Working Principle

When the power supply\'s input voltage reaches the start-up voltage threshold, the integrated high-side power MOSFET turns on and draws the external inductor current. This current is then limited by a current-sense resistor or built-in current-sense circuit. In normal operation, the output current feeds the integrated MOSFET and the output voltage rises as the inductor current increases. The duty cycle (D) is calculated through a cycle-by-cycle current-mode control. TPS61254YFFT constantly monitors the voltage on the high-side MOSFET and turns it off when the output current is limited to the set maximum. The high-side MOSFET is turned back on if the load current falls below the set threshold.

For multiple cell Li-ion applications, a battery charger control (BCC) pin can be used to delay the turn-on of the power MOSFET. This way, TPS61254YFFT won\'t be powered up until the Li-ion battery voltage reaches the BCC voltage. This feature helps to extend the life of the battery by preventing an excessive current draw from the Li-ion cell when the battery is depleted.

The internal voltage loop keeps the output voltage accurate by comparing the FB pin voltage with the reference. The voltage difference is then buffered and amplified before being fed back into the integrated PWM comparator, which in turns keeps the output voltage regulated. A voltage compensation block is also integrated in order to improve the transient response. The voltage loop bandwidth is adjusted using an external resistor and capacitor.

An external compensation network is also needed and its time constants are set according to the value of the output voltage. A lower output voltage gives a longer time constant, making the loop more stable.

Conclusion

TPS61254YFFT belongs to PMIC (Power Management ICs) voltage regulators called DC DC Switching Regulators and is suitable for many applications such as cellular phones, handsets, PDAs, portable stereo players, portable DVD players, portable digital cameras and portable gaming consoles. Its current-mode control topology and integrated soft start, power-saving stages and thermal shutdown protection features make it a reliable and accurate device.