Galvanic isolation is used in a variety of medical and industrial applications to isolation a circuit at a high voltage potential from a circuit at a low voltage potential. This isolation prevents excessive voltages from either circuit from reaching the other circuit. This presentation outlines a semiconductor transformer method developed by the AMS foundry to place transformers in silicon on to achieve such isolation between two CMOS high-voltage die in the same plastic package. This capability is available from Triad Semiconductor and AMS.

1. Galvanic Isolation & RS485
Triad Semiconductor - The Configurable Mixed Signal ASIC Company

2. Galvanic Isolation
 Galvanic isolation contained in IC1
- IC2 ground at 450V
- IC1 ground at 0V
 Inductive coupling of signals
between IC2 and IC1
 Isolation Coils (transformer) can be
built in various device layers
 Signals in IC1 and IC2 are
modulated before transmission
across the Galvanic Transformer
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3. Galvanic Isolation Capabilities
Inductive coupling
between layers
Continuous
10 y / 150 C / 10ppm
Transient
100s / 150 C / 10ppm
Metal-1 to Metal-3
207Vrms, 290VDC
2.1kVrms
Substrate to Metal-3
300Vrms, 423VDC
3.0kVrms
Metal-1 to Metal-4
330Vrms, 465VDC
3.3kVrms
Substrate to Metal-4
420Vrms, 590VDC
4.2kVrms
Galvanic isolation guidelines for inductive coupling between different process layers.
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4. Galvanic Isolation Encode / Decode
 Signals encoded (modulated) to allow for transmission though the inductive loop
 Signals decoded (demodulated) after inductive loop to baseband and DC signals
High-Side VCA Die
Low-Side VCA Die
Decode
Encode
Encode
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Galvanic
Isolation
Inductive
Coil
Galvanic
Isolation
Inductive
Coil
Decode
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5. Galvanic Isolation within a System-In-Package Solution
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6. RS-485 Overview
RS-485 is a half-duplex, 2-wire, multi-drop
communications implementation
- Physical layer specification only
- No communication protocol is implied
- Differential twisted-pair increases noise
immunity
- Data rates from 10’s of Kbps to 10’s of Mbps
Applications include
- Industrial process monitoring and control
- Factory automation
- Robotics motor control
- Serial communications requiring a more robust
electrical interface when compared to RS-232
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7. Triad RS-485 IP Block Highlights
- One transmitter / one receiver
- Separate TX/RX enables
- Thermal cutoff and short circuit protection
- Pre-compensation filter and programmable slew rate for enhanced performance
over long transmission lines
• Analog power (VDD) from 8V to 15V
IO
IOVOLTS
VDD
TXEN
IO
220k
VCC
220k
sl e
• Digital I/O from 1.5V to 5.5V
• Data rates up to 500Kbps
E
TXIN
IO
• Analog I/O (VCC) from 3V to VDD
w
• Common mode range from -10V to
+12V
220k
PRECOMP
on/off
• BUS+/- ports tolerant to +/- 45V
BUS-
RXOUT
BUS+
• 120mA drive capability
/RXEN
220k
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GND
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8. Key Parameter Comparison with RS-485 Standard
Max Number of Transmitters/Receivers on Bus
Standard requires 32...
Triad IP supports 64!
...
...
...
...
...
...
Max Cable Length
Standard requires 4,000 ft...
Triad IP supports 14,000 ft!
OR
Up to 10 stubs of 2,500 ft each (25,000 ft total length)!
** Pre-compensation filter and programmable slew-rate allow
communicating over long lengths
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