AFE5801 datasheet(37/46 Pages) TI

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SNR + 10Log10

AFE5801

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SLOS591D – SEPTEMBER 2008 – REVISED MAY 2010

DEFINITION OF SPECIFICATIONS

Analog Bandwidth – The analog input frequency at which the power of the fundamental is reduced by 3 dB with

respect to the low frequency value.

Aperture Delay –The delay in time between the rising or the falling edge of the input sampling clock (depending

on the channel) and the actual time at which the sampling occurs. This delay will be different across channels.

The maximum variation is specified as aperture delay variation (channel-channel).

Aperture Uncertainty (Jitter) – The sample-to-sample variation in aperture delay.

Clock Pulse Width/Duty Cycle – The duty cycle of a clock signal is the ratio of the time the clock signal remains

at a logic high (clock pulse width) to the period of the clock signal. Duty cycle is typically expressed as a

percentage. A perfect differential sine-wave clock results in a 50% duty cycle.

Maximum Conversion Rate – The maximum sampling rate at which certified operation is given. All parametric

testing is performed at this sampling rate unless otherwise noted.

Minimum Conversion Rate – The minimum sampling rate at which the ADC functions.

Differential Nonlinearity (DNL) – An ideal ADC exhibits code transitions at analog input values spaced exactly

1 LSB apart. The DNL is the deviation of any single step from this ideal value, measured in units of LSBs.

Integral Nonlinearity (INL) – The INL is the deviation of the ADC's transfer function from a best fit line

determined by a least squares curve fit of that transfer function, measured in units of LSBs.

Gain Error – The difference between the actual gain of a channel & its ideal (theoretical) gain, i.e., the error in

the absolute gain of the channel.

Gain Matching – The gain difference between two channels with same theoretical gain setting. For perfect

matching, the difference should be zero. On the context of this device, the gain matching is obtained in two

different ways:

1. The values on the specification table represent the expected gain matching between any two channels on

the system. The gain is measured on every channel of every device, for a given gain setting, at any

temperature. The difference between the maximum recorded gain and the minimum recorded gain

represents the gain matching at that given gain setting. The same is done for every gain setting and the

maximum difference for any gain setting is presented on the table.

2. The gain matching histogram represents the channel to channel matching inside the same device, i.e., the

maximum expected gain difference between any two channels of the same device, or in other words, the

peak-to-peak variation of absolute gains across all channels in the device. At a given gain setting for all the

channels of a given device (at one temperature assumed common to the whole device), the difference

between the channel with maximum gain and the channel with minimum gain represents one count. The

same thing is done for all the devices and for 3 temperatures (–40C, 25C and 85C). Every measurement of a

device at one given temperature represents one count.

Offset Error – The offset error is the difference, given in mV, between the ADC's actual average idle-channel

output code and the ideal average idle-channel output code.

Temperature Drift – The temperature drift coefficient (with respect to gain error and offset error) specifies the

change per degree Celsius of the parameter from TMIN to TMAX. It is calculated by dividing the maximum deviation

of the parameter across the TMIN to TMAX range by the difference TMAX – TMIN.

Signal-to-Noise Ratio – SNR is the ratio of the power of the fundamental (PS) to the noise floor power (PN),

excluding the power at DC and the first nine harmonics.

(1)

SNR is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the

reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the full-scale

converter range.

Signal-to-Noise and Distortion (SINAD) – SINAD is the ratio of the power of the fundamental (PS) to the power

of all the other spectral components including noise (PN) and distortion (PD), but excluding dc.

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