Important Issue with RHS Headstages, Controllers, and RHS2116 Chips
May 12, 2021
In May 2021, Intan identified a hardware degradation mode in the Intan RHS2116 chips used in our RHS stim/record headstages. When powering these chips from a ±9V supply, the anodic (positive) current generator in each stimulator circuit begins to fail after many stimulation pulses, typically in the range of 30,000 to 1 million stimulation pulses. After degradation, the positive current output will be too low, often zero. This is a permanent hardware failure that cannot be reset by power-cycling the device.
The cathodic (negative) current generators do not degrade, so in most applications neural tissue will still be activated but due to the absence of anodic current, change balance will not be maintained.
We have run extensive tests at Intan and determined that lowering the supply voltage to ±7V protects the chip against these failures. We have tested RHS headstages to more than 100 million stimulation pulses at these supply levels with no anodic current failures observed.
We therefore request that any users who purchased an RHS stimulation/recording controller before May 2021 contact us to arrange returning the unit for free retrofitting to reduce the voltage supplies on the four headstage ports from ±9V to ±7V. This will reduce the ability of headstages to drive currents into higher-impedance electrodes by about 25%, but it is unlikely to have a practical impact on most users.
Customers may also return any RHS stim/record headstages and we will test them and replace any units that show damaged anodic current generators.
If you are unsure if your RHS stimulation/recording controller has been modified for ±7V operation, look on the back panel near the USB port. All controllers built or modified for ±7V operation will have a red 7V label near the USB port:
RHS2116 Chips
All customers using RHS2116 chips in custom hardware applications are advised to reduce power supplies to ±7V (or a total voltage difference between VSTIM+ and VSTIM- of no more than 14V) to avoid long-term degradation of anodic current generators on the chip.
We announced this issue in our Intan email newsletter on May 12, 2021. If you are not subscribed to our newsletter, you may sign up at the bottom of this page.
Please contact us if you have any questions or concerns about this issue. We apologize for any inconvenience but will do everything we can to repair existing systems as quickly as possible.
