The BAL-2593D5U and BAL-2690D3U are integrated baluns used to convert
the antenna signal to a balanced pair of signals as required by the
Bluetooth transceiver. As replacements for traditional baluns built
with discrete components, the integrated baluns occupy up to 70 percent
less printed-circuit-board area, simplify design and assembly and
improve wireless performance, ST claimed.

The ICs include the wound transformers and integrated passive devices fabricated using a glass substrate.

The BAL-2593D5U is optimized for use with the STLC2500D
standalone Bluetooth transceiver and STLC2592/3 combo devices, which
implement an FM radio tuner enabling users to listen to radio directly
on a Bluetooth headset. The BAL-2690D3U is designed to partner the
STLC2690, a Bluetooth/FM-tuner combo that also adds a short-range FM
transmitter allowing the user to play stored music through a system
such as a car radio.

The BAL-2593D5U offers an impedance of 50/50+j50 ohm and 1.2-dB
insertion loss, in a 1.16-mm by 1.26-mm footprint. The component is
under 0.7-mm high. The BAL-2690D3U offers an impedance of 50/30+j25 ohm
and 0.8-dB insertion loss, in a 0.91-mm by 0.91-mm footprint and the
same profile.

The BAL-2593D5U and BAL-2690D3U are in production in 4-bump
flip-chip packages, priced at $0.25 for a minimum order of 5000 pieces.