IP holds down power in always-on logic, in TSMC 55 ULP / ULP-eF process

January 25, 2016 // By Graham Prophet
Devices for mobile applications, IP vendor Dolphin Integration observes, spend most of the time in deep-sleep mode and it is essential to minimise the energy drawn by the always-operating functions. Dophin has developed a reliable methodology for defining the minimum operating voltage, based on a trade-off between operating speed and power consumption, while guaranteeing the best yield.

Using this approach, the standard cell validation and characterisation flow is tuned for both accuracy and reliability. The extremely low-voltage SESAME eLV library uses this design methodology and employs a patented flip-flop to achieve minimal power consumption.

SESAME eLV is designed to operate down to the minimum data retention voltage (0.55 V at TSMC 55nm uLPeFlash) allowing the designer to share the same supply voltage for always-on logic and retention RAM, if any. The advantage is to avoid a dedicated regulator for always-on logic, saving both area and power.

Operating at such a low voltage allows very significant power savings: power consumption can be divided by more than a factor of two when supplying the always-on logic at 0.55V compared to 1.2V.

However, Dolphin adds, ultra-low voltage operation also comes with a trade-off on maximum operating frequency. Therefore, the SESAME eLV library is available in different configurations (6 & 9 tracks, SVT & HVT, different PVT corners) in order to cover a wide range of needs. For TSMC 55 nm uLPeFlash, standard deliverables include characterisation at 0.55V for designs operating at a few tens of kHz – typically, an RTC at 32 kHz – and at 0.75 V for operation at a few MHz – typically, a wake-up trigger based on Voice Activity Detection (VAD).

Sesame eLV features



Dual/Low voltage

Dynamic and leakage power reduction

From 1.2 V +/-10%

To 0.55 V +/-10%

Multiple VTs

Best trade-off

between Speed & Leakage



Characterization corners

Custom PVT support to reach the best speed vs. power compromise in the range [0.55V-1.2V]

Dolphin Integration provides a complete set of complementary products to build an ultra low-power always-on block:

  • qLR Della Aon – Dual Output: an optimised cap-less LDO with dual output that enables supplying both standard IO cells and the ultra low-power always-on block.

  • Ultra low-power RC and crystal oscillators

  • qCMPH comparator , a low-power voltage trigger

  • Whisper Trigger ,