BMD101 Product Brief (Preliminary) 2012

NeuroSky BMD101 Product Brief Rev 0.9.2

NeuroSky Confidential

Page 6

BMD101 has built-in sensor-off detection capability. Any resistance between two sensor input pins that

exceeds typically 19-25 Meg Ohms will trigger the sensor-off status.

Also, the BMD101 contains an internal LDO which consists of a bandgap cell to generate a 1.2V

reference followed by two separate unity gain buffers, for the analog and digital supplies.

A digitally controlled oscillator (DCO) is included in the BMD101 as well, which provides a fully

integrated 22.1MHz clock reference signal.

The majority of the filtering of the bio-signal in this system will be done in the digital domain. It is

expected that the main interferers is due to pick-up of the local power-supply frequency, i.e. 50Hz or

60Hz, depending on the geographical region.

The BMD101 has low DC offset levels as referred to the input of the ASIC, very low input referred noise

and a low noise floor. It has good SNR and very good ENOB for the ECG application ranges. BMD101

CMRR levels are also very low.

Digital Signal Processing

After data leaves the ADC it goes through the digital filters per Figure 2.

Configurable

Notch Filter

50Hz or 60Hz or

both

Low-Pass-Filter

(100Hz Cut-off Freq)

HBAv

Raw Data

ADC

UART

Figure 2. Digital Signal Processing Data Path

Notch Filter

The Notch Filter is typically customized to be a 50Hz or 60Hz or both notch through configuration. The

notch rejection is usually -63dB for both 60Hz and 50Hz.

Low Pass Filter

The Low Pass Filter has 100Hz cutoff frequency. It provides a stable passband to the cutoff frequency,

and -40dB at the stop frequency.