ADPD6000 datasheet(21/89 Pages) AD

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Data Sheet

ADPD6000

THEORY OF OPERATION

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Rev. 0 | 21 of 89

VOUT=0.8×BIOZ_SINEAMPLITUDE_x

211

Vp‐p (2)

Frequency= 32M×BIOZ_SINEFCW_x_x

226

Hz (3)

BIOZ_DAC_GAIN_x and BIOZ_DAC_OFFSET_x are used to give

more flexible control of the generated sine wave for different appli-

cations.

The TIA gain can be accessed through BIOZ_TIA_RGAIN_x.

After digitizing the measurement, the ADC output is sent to the

datapath of the BIA channel, which includes filters, gain controls,

and the DFT path (see the Datapath section for more information).

The DFT result is I data and Q data of the received sine wave, and

the data format is 18 bits.

When the chain turns on, the DFT path can wait before

performing the DFT. The waiting time is controlled by BI-

OZ_ADC_CONV_DLY_x.

For accurate measurement, the chip must perform ratio measure-

ment. That is, the chip needs to measure the known external

resistor at the RCALP and RCALN pins, and then measure the

unknown resistor. Use the ratio method to calculate the resistor

under test.

FIFO

The FIFO is never written with partial packets of data. If there is not

enough room for the data that is written to the FIFO for all enabled

time slots and any selected status bytes, no data is written from

any of the time slots during that period and the INT_FIFO_OFLOW

status bit is set.

The order of samples written to the FIFO (if selected) is dark

followed by lit data. Table 11 shows the byte order for multibyte

words.

Table 11. Byte Order for FIFO Writes

Size

Byte Order (After Shift)

[7:0]

[15:8], [7:0]

[23:16], [15:8], [7:0]

[31:24], [23:16], [15:8], [7:0]

The FIFO size is 640 bytes. When the FIFO is empty, a read

operation returns 0xFF and the INT_FIFO_UFLOW status bit is set.

ECG Data Format

The data in the ECG is channel is 24-bit unsigned data with a

status byte as a header. Figure 33 shows the data in the ECG

channel.

Figure 33. ECG Data Format

If ENA_STAT_ECG is set to 1, the ECG output data is a 4-byte

structure, where the highest byte is the ECG related status informa-

tion. If ENA_STAT_ECG is set to 0, the ECG output data is a 3-byte

structure with only ECG channel output data.

PPG Data Format

At the end of each time slot, the selected data is written to the

FIFO. The packet can include 0-, 8-, 16-, 24-, or 32-bit data for

each of the dark data, signal data, or lit data values. The bit

alignment of the data written to the FIFO is selectable with a shift

of 0 bits to 31 bits, with saturation provided. Lower bits are ignored.

The DARK_SIZE_x, LIT_SIZE_x and SIGNAL_SIZE_x bits select

the number of bytes of each field to be written from 0 bytes to 4

bytes. When set to 0, no data is written for that data type. The

DARK_SHIFT_x, LIT_SHIFT_x, and SIGNAL_SHIFT_x bits select

the number bits to shift the output data to the right before writing

the FIFO. If there are any significant bits at more significant bit

positions than those selected, the data written to the FIFO is

saturated.

The order of samples written to the FIFO (if selected) is signal

data followed by dark data and then lit data. If both channels are

enabled, all selected Channel 1 data values are written to the FIFO

first, followed by the Channel 2 data.

For example, in modes that use dark data, the eight upper bits of

the dark data can be stored with 24 appropriately selected bits from

the signal data for each time slot. This method detects whether

the ambient light is becoming large, while limiting the size of the

amount of data transferred.

PPG Data Format shows the PPG data format in the FIFO.

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