ADPD4001 datasheet(32/82 Pages) AD

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ADPD4000/ADPD4001

Data Sheet

Rev. A | Page 32 of 82

PRECONDITION

SENSOR

MODULATE

STIMULUS

–

INTEGRATION

SEQUENCE

ADC CH1

START OF TIME SLOT

MOD_OFFSET_x

MOD_WIDTH_x

INTEG_OFFSET_x + INTEG_FINE_OFFSET_x

INTEG_WIDTH_x

TIA OUTPUT

INTEGRATOR

OUTPUT

PERIOD

(AUTOMATICALLY CALCULATED)

–

PRE_WIDTH_x

(DEFAULT 8µs)

Figure 39. Timing Diagram for Modulate Stimulus Operation

Table 21. Modulate Stimulus Settings

Group

Time Slot A

Bit Field Name

Description

Modulate Stimulus

Setup

0x0100

SAMPLE_TYPE_x

Leave at the default setting (0) for default sampling mode.

0x0101

AFE_PATH_CFG_x

Set to 0x0E6 for TIA, integrator, and ADC. Bypass BPF.

0x0102

INPxx_x

Enable desired inputs.

0x0103

PRECON_x

Set to 0x5 to precondition sensor to TIA_VREF.

0x0103

VCx_PULSE_x

VCx pulse control. Set to 0x2 to pulse to the alternate

voltage during a modulation pulse.

0x0103

VCx_ALT_x

Select the alternate state for VCx during the modulation

pulse.

0x0103

VCx_SEL_x

Set to 0x1 to set VCx to TIA_VREF as primary state.

0x0104

TIA_GAIN_CHx_x

Select TIA gain.

0x0104

AFE_TRIM_VREF_x

Set to 0x2 to set TIA_VREF = 0.9 V.

Modulate Stimulus

Timing

0x010C

MOD_OFFSET_x

Sets start time of first modulation pulse in 1 μs

increments.

0x010C

MOD_WIDTH_x

Sets width of modulation pulse in 1 μs increments. Typical

values of 6 μs to 12 μs.

0x010A

INTEG_WIDTH_x

Integration time in µs. Set to MOD_WIDTH_x + 1.

0x010B

INTEG_OFFSET_x

Integration sequence start time. Set to MOD_OFFSET_x − 1.

0x010B

INTEG_FINE_OFFSET_x

Start from 0 and sweep to find optimal operating point.

0x0107

NUM_INT_x

Set to 1 for a single integration per ADC conversion

0x0107

NUM_REPEAT_x

Number of sequence repeats. SNR increases as √n. where

n = NUM_REPEAT × NUM_INT.

This is the Time Slot A register address. Add 0x020 for the identical register address for each subsequent time slot. For example, Register 0x0100 is the location for

SAMPLE_TYPE_A. For Time Slot B, this register is at Address 0x0120. For Time Slot C, this register is at Address 0x0140. For Time Slot D, this register is at

Address 0x0160, and so on.

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