Chipanalog CA-IS3020S

CA-IS3020 and CA-IS3021 are low-power bidirectional I²C-compatible isolators. The input and output sides are electrically isolated by a high-voltage isolation capacitor constructed from silicon dioxide (SiO₂). The CA-IS302x series provides up to 5kVrms isolation, preventing noise and surges on the data bus or other circuits from reaching the local ground and interfering with or damaging sensitive circuitry. A CMTI rating of up to 150kV/μs ensures correct signal transmission in harsh noise environments.

The CA-IS3020 supports bidirectional transmission on both the SDA and SCK channels; the CA-IS3021 supports bidirectional communication on the SDA channel but uses a unidirectional SCK channel. The CA-IS3020 is suited for multi-master applications, while the CA-IS3021 is suited for single-master applications. If there is any possibility that a slave device may pull down the clock line in the actual application, the CA-IS3020 must be used.

The I²C bus is widely used in industrial applications, many of which require electrical isolation to eliminate ground loops. The I²C bus comprises two open-drain bidirectional lines — SCL and SDA — supporting data and clock transfer between one master and multiple slaves. The master controls bus timing via SCL, while data is transferred between master and slaves via SDA.

Unlike standard unidirectional digital isolators, an I²C isolator must operate in bidirectional communication mode. Simply connecting two opposing unidirectional digital isolation channels in parallel to form a bidirectional isolator will cause a low-level deadlock on the bus. Although this issue can be resolved by adding external anti-deadlock circuitry, doing so increases component count, board area, and cost. The CA-IS302x series provides a single-chip isolated I²C solution that requires no external components other than decoupling capacitors between VCC and GND and pull-up resistors on the I²C bus. The logic inputs and output drivers on both sides of the chip are safely isolated up to 5kVrms through on-chip SiO₂.

The CA-IS302x I²C isolators internally split the bidirectional SCL/SDA lines into two unidirectional digital signal channels. The output driver of each digital channel is an I²C-compatible open-drain output. Side A of the CA-IS302x connects to the low-capacitance node of the I²C bus, supporting a maximum load capacitance of 40pF; Side B connects to the high-capacitance node, supporting a maximum load capacitance of 400pF. An internal anti-deadlock circuit raises the SCL/SDA low-level output voltage on Side A to approximately 700mV. The Side A logic input is evaluated by an internal hysteresis comparator, which distinguishes between a low level pulled directly down by the SDA bus (not exceeding 400mV) and a low level elevated to 700mV by the Side A output driver. This mechanism determines the signal transmission direction on the SCL/SDA lines at any given time.

• Isolated bidirectional communication, compatible with I²C bus protocol
• Signal transmission rate: DC to 1MHz
• Wide supply voltage range: 3V to 5.5V
• Wide temperature range: -55°C to 125°C
• Open-drain output, Side A with 3.5mA current sink capability
• Side B with 35mA current sink capability
• Excellent electromagnetic immunity
• CMTI: ±150kV/μS
• Surge: 10kV
• ESD: 8kV
• Isolation voltage up to 5kVrms
• Isolation barrier lifetime: >40 years
• Package: SOIC8, Wide-body SOIC8
• RoHS compliant

• Isolated I²C bus
• SMBus and PMBus interface
• Motor drive systems
• I²C level translation