The company had a first version of the wireless back stimulator chip, but it was sensitive to environmental conditions (voltage and temperature variations) and yielded poorly. There was an incomplete specification for the first device and the design database was not available. The assembly for the device required a long thin aspect ratio – beyond the generally practiced limits. It also had a requirement to be bonded to a flexible circuit board for insertion in a narrow tube (to be inserted in the back of the patient).


iSine engineers reviewed the design goals for the device with the customer and developed a new specification for the ASIC. The design spec was reviewed and accepted by the customer.

Special consideration was made in the design of the ASIC to ensure it was not as susceptible to environmental conditions. It was developed in a mature semiconductor process node with good yield.

The design was performed using SPICE modeling for the analog sections and VHDL for the digital sections. I/O cells and power-and-ground pads were custom designed to meet the low power, high performance requirements.

The final assembly needed to have the die delivered with solder balls for attachment to the flexible circuit board. iSine directed the assembly house to attach the correct size solder balls and to provide the devices in a tape-and-reel format to allow for easier final assembly.


The ASIC met all of the goals as defined in the specifications and was successful in meeting the customer requirements. It is shipping in volume and in use by the end customer.

It met both the schedule and cost goals set forth by the customer at the start of the project and is yielding well in the final assembly.

The ASIC was integrated in X-Fab’s 0.35µm technology.

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