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INDICE Semiconductor
High Resolution Digital amplifiers
enabled by Continuous Sigma
April 2015
CONTINUOUS SIGMA ENCODING
A breakthrough in high resolution, switched amplifiers
Continuous Sigma is Indice’s proprietary power control
algorithm that is able to remove switch-mode bridge error
and noise in real time, offering a breakthrough in high
resolution audio whilst maintaining ultra high efficiency.
We address the limitations of Class D amplifiers which
inherently introduce inter-modulation and harmonic
distortion due to the carrier frequency modulation and
inadequate adaptation rates.
Indice’s amplifier uses a multi-feedback system which
naturally rejects switching and power supply noise.
WHY CHOOSE INDICE?
Indice’s proprietary continuous sigma control offers
the following benefits covered in the slides:
•High Resolution audio (HRA) ready
•High frequency adaption rate
•Flat gain curve
•Spread spectrum EMI profile
•Bridge Tied load (BTL) standard offering
•Multiple feedback nodes
•High efficiency
High Resolution – Fast adaptation rate
The unique nature of Continuous Sigma is it is
adapting at the switching rate which enables more
accurate reproduction of the source music
•Algorithm:
Continuous Sigma
•Decision speed: 1MHz
•Sample b/w:
192KHz
Traditional Class D
~44KHz
44KHz
Switching frequency comparison
Continuous Sigma enables INDICE to make switching
decisions at the carrier frequency delivering superior
performance and a high resolution audio experience
Class D
decision
speed
44KHz
Class D
switching
frequency
200KHz
400KHz
INDICE switching
speed and decision
speed
600KHz
800KHz
1MHz
Class-AB amplifier crossover distortion
INDICE’s Continuous Sigma amplifiers do not suffer from
crossover distortion that is experienced in Class-AB
amplifiers
INDICE delivers a flat gain curve
Continuous sigma enables a very flat gain curve to
accurately reproduce the source music with the clarity of
Class A but with the efficiency of a digital amplifier.
Continuous sigma does not suffer compression like other
switching amplifiers which leads to higher THD.
Green = INDICE
Highly uniform frequency response
The flat gain curve and highly linear nature of Continuous
Sigma delivers an highly uniform frequency response
INDICE amplifiers are BTL (Bridge Tied
Loads)
All INDICE amplifiers are BTL which means that
they can run from a single supply rail, reducing
system cost while maintaining excellent frequency
response and performance.
Amplifiers that are not BTL have to factor in higher
system costs for the additional power supply rail.
EMI filter advantages
Most Class D amplifiers require the carrier to be present at
the speaker, Indice’s amplifiers do not as the feedback
network is before the output stage filter enabling a higher
attenuation filter to reduce speaker cable RF emissions
Class D feedback node
INDICE feedback node
Spread spectrum EMI profile
Continuous sigma is asynchronous so there is no
fixed carrier frequency that leads to a large EMI peak
or subsequent harmonics.
Traditional Class D
INDICE
High Efficiency gives freedom for
design
Continuous sigma enables efficiency >96% which reduces
heatsink design, in many applications the external heatsink can
be eliminated or reduced in size
EXTERNAL
HEATSINK
FREE
INDICE Blade
TAS5611A
>96%
~89%
4W
11W
Efficiency:
Pd @ 100WRMS:
Precise speaker position control
The BLADE has a very high damping factor (DF) enabling very
precise control of the speaker and fast attack and fade
Incredible audio fidelity
THD+N performance in a very cost effective package
INDICE BLADE IN81
vs TI TAS5611A D-CLASS IC
Description of Feature
INDICE
Texas Instruments
BLADE IN81
TAS5611A
Control technique
Continuous Sigma
PurePath HD
Power Bandwidth
50KHz / 100KHz*
44KHz
Rated power (1% THD into 4Ω)
91W (without heatsinking)
60W (heatsinked)
Maximum power rating (1% THD)
364W @1Ω
125W @2Ω
Efficiency (80% load, 4Ω)
96%
89%
Signal to Noise Ratio (Supply = 24V, Load = 4Ω, A-weighted)
122dB
100dB
THD+N (Supply = 24V, Load = 4Ω)
0.004%
0.05%
Idle Power consumption (Control circuit only)
200mW
750mW
Output noise (VCC = 24V)
34uV
168uV
Differential input range
4VRMS
0 – 5Vp-p
Power supply ripple rejection (PSSR)
-77dB (Vripple=1VRMS@100Hz)
Not specified
Switching frequency
Asynchronous up to 1.2MHz
400KHz
www.indicesemi.com
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