Smart-antenna controller saves board space in smartphones
Saving board space, bill of materials and battery load, STMicroelectronics’ STHVDAC-253C7 digital controller can be used with for tunable capacitors such as ST’s STPTIC family, to save the power consumption of antenna-tuning circuits used to stabilise smartphone RF performance. Using the STHVDAC-253C7 with STPTIC capacitors for impedance matching and frequency tuning almost completely eliminates the effects of environmental variations, says ST, resulting in stronger signal reception, fewer dropped calls, faster data rates, and longer battery life for handset users.
The controller uses ST’s 0.18 micron BCD8 process and 0.35mm-pitch flip-chip package, making the STHVDAC-253C7 50 per cent smaller than its predecessor and consuming half the operating current. The controller works with the latest 0402 chip-size inductors and requires no external Schottky diode, reducing the overall circuit footprint even further, adds ST.
As a high-voltage digital to analogue converter (DAC) specifically designed to generate bias voltages for tunable capacitors, the STHVDAC-253C7 provides three outputs suitable for tuning three different capacitances in multi-band GSM/WCDMA/LTE handsets. ST has also integrated the boost converter needed to generate bias voltages across the full capacitor-tuning range from 0 to 24V. The STHVDAC-253C7 accepts standard MIPI RFFE (RF front end) commands from the system transceiver. Support for three RFFE unique slave IDs (USID) allows a single STHVDAC-253C7 to manage up to three separate antennae.
The STHVDAC-253C7 supports commonly used antenna-tuning modes, including normal mode, which moves to a newly commanded output voltage within 10 micro seconds, turbo mode, optimised for minimum settling time and glide mode, with programmable delay from 512 micro seconds to 16.84milliseconds for the smoothest transitions and to meet requirements such as 3GPP phase discontinuity. A general purpose input/output (GPIO) pin can be used for managing two controllers on the same RFFE bus in dual-tuner handsets. It also allows switching between registers to manage antenna-diversity designs or adjust settings to correct the antenna response when a USB cable is plugged in.
The STHVDAC-253C7 is supplied in a 12-bump 0.35mm pitch, flip chip, WLCSP.
