原标题：ADI ADPD4000(1)多模式传感器前端解决方案

ADI公司的ADPD4000是多模式传感器前端,有8 个输入通道, 具有多种工作模式以适应以下测量如PPG,ECG,EDA,阻抗和温度.有12 个可编程时隙,适用于同步传感器测量. 灵活的采样速率从0.004 Hz 至 9 kHz,片内集成了数字滤波,发射和接收信号链的SNR为90 dB,环境光抑制为60 dB 至 1 kHz,支持 SPI 和 I²C 通信, 256 字节 FIFO.主要用在可穿戴健康和健美监视器如心率监视仪(HRM),心律变异(HRV),应力,血压估计, SpO2,水化（合）作用,体躯成分.工业监测如CO,CO2,烟雾,气溶胶检测以及家庭病人监测.本文介绍了ADPD4000/1主要特性,功能框图, 模拟信号通路框图以及评估板EVAL-ADPD4000Z-PPG和EVAL-ADPDUCZ连接图,评估板EVAL-ADPD4000Z-PPG主要特性,电路图和PCB设计图.

The ADPD4000/ADPD4001 operate as a complete multimodal sensor front end, stimulating up to eight LEDs and measuring the return signal on up to eight separate current inputs. Twelve time slots are available, enabling 12 separate measurements per sampling period. 

The data output and functional configuration utilize an I2C interface on the ADPD4001 or a serial port interface (SPI) on the ADPD4000. The control circuitry includes flexible LED signaling and synchronous detection. The devices use a 1.8 V analog core and 1.8 V/3.3 V compatible digital input/output (I/O). 

The analog front end (AFE) rejects signal offsets and corruption from asynchronous modulated interference, typically from ambient light, eliminating the need for optical filters or externally controlled dc cancellation circuitry. Multiple operating modes are provided, enabling the ADPD4000/ ADPD4001 to be a sensor hub for synchronous measurements of photodiodes, biopotential electrodes, resistance, capacitance, and temperature sensors.

The ADPD4000/ADPD4001 are available in a 3.11 mm × 2.14 mm, 0.4 mm pitch, 33-ball WLCSP and 35-ball WLCSP.

ADPD4000/1主要特性: 

Multimodal analog front end 
8 input channels with multiple operation modes to accommodate the following measurements: PPG, ECG, EDA, impedance, and temperature 
Dual channel processing with simultaneous sampling 
12 programmable time slots for synchronized sensor measurements 
Flexible input multiplexing to support differential and single-ended sensor measurements 
8 LED drivers, 4 of which can be driven simultaneously 
Flexible sampling rate from 0.004 Hz to 9 kHz using internal oscillators 
On-chip digital filtering 
SNR of transmit and receive signal chain: 90 dB 
Ambient light rejection: 60 dB up to 1 kHz 
400 mA total LED drive current 
Total system power dissipation: 50 μW (combined LED and AFE power), continuous PPG measurement at 75 dB SNR, 25 Hz ODR, 100 nA/mA CTR 
SPI and I2C communications supported 
256-byte FIFO 

ADPD4000/1应用:

Wearable health and fitness monitors: heart rate monitors (HRMs), heart rate variability (HRV), stress, blood pressure estimation, SpO2, hydration, body composition 
Industrial monitoring: CO, CO2, smoke, and aerosol detection 
Home patient monitoring

图1. ADPD4000/1功能框图

图2. ADPD4000/1模拟信号通路框图

评估板EVAL-ADPD4000Z-PPG 

The EVAL-ADPD4000Z-PPG evaluation board provides users with a simple means of evaluating the ADPD4000/ADPD4001 photometric front end. 

The EVAL-ADPD4000Z-PPG evaluation board implements a simple discrete optical design for vital signs monitoring applica-tions, specifically wrist-based photoplethysmography (PPG).

The EVAL-ADPD4000Z-PPG has three green light emitting diodes (LEDs), one infrared (IR), and one red LED, all separately driven. A single 7 mm2 photodiode (PD) is populated on the board. The PD has no optical filter coating. However, a pin for pin alternative device with an IR block filter is available. 
The full evaluation system includes the Wavetool Evaluation Software graphical user interface (GUI) that provides users with low level register access and high level system configurability. Raw data streamed to this tool can be displayed in real time with limited latency. Views are provided for both frequency and time domain analysis. 

A user datagram protocol (UDP) transfer capability from the Wavetool Evaluation Software (available for download on the EVAL-ADPD4000Z-PPG product page) allows data stream connections and register configurability to external analysis programs, such as LabVIEW® or MATLAB®, in real time. 

The EVAL-ADPD4000Z-PPG board is powered by the EVAL-ADPDUCZ microcontroller board (obtained from the EVAL-ADPD4000Z-PPG product page). In addition to the power requirements, serial port interface (SPI) (default) or I2C data streams are received from the ADPD4000 by the microcontroller. A ribbon cable connects the two boards. The microcontroller repackages the data, sending it to a virtual serial port over the USB to the PC, displayed on the Wavetool Evaluation Software. The EVAL-ADPD4000Z-PPG can also be connected directly to the microcontroller development system of the user, using the SPI for the ADPD4000 (or I2C for the ADPD4001). 

The ADPD4000/ADPD4001 data sheet, available at www.analog.com, provides full specifications for the ADPD4000/ADPD4001. Consult the ADPD4000/ADPD4001 data sheet in conjunction with this user guide when using the EVAL-ADPD4000Z-PPG.

评估板EVAL-ADPD4000Z-PPG主要特性:

Board supports ADPD4000 and ADPD4001 population 
ADPD4000 (SPI) is the default board population 
All inputs and outputs are accessible to the user 
3 separately driven green LEDs included 
1 red and 1 IR LED included 
Metal baffle to block optical crosstalk 
Works with the Wavetool Evaluation Software allowing 
Time domain graphing and logging 
Frequency domain graphing 
Statistical analysis 
Data streaming to other applications 

评估板EVAL-ADPD4000Z-PPG 包括:

EVAL-ADPD4000Z-PPG evaluation board 
Ribbon cable 
Wrist strap, with hook and loop fastener

图3. 评估板EVAL-ADPD4000Z-PPG外形图(顶视)

图4. 评估板EVAL-ADPD4000Z-PPG外形图(底视)

图5.评估板EVAL-ADPD4000Z-PPG和EVAL-ADPDUCZ连接图

图6. 评估板EVAL-ADPD4000Z-PPG电路图(1)

图7. 评估板EVAL-ADPD4000Z-PPG电路图(2)

图8. 评估板EVAL-ADPD4000Z-PPG PCB设计图(1)

图9. 评估板EVAL-ADPD4000Z-PPG PCB设计图(2)

图10. 评估板EVAL-ADPD4000Z-PPG PCB设计图(3)

图11. 评估板EVAL-ADPD4000Z-PPG PCB设计图(4)

图12. 评估板EVAL-ADPD4000Z-PPG PCB设计图(5)

图13. 评估板EVAL-ADPD4000Z-PPG PCB设计图(6)

图14. 评估板EVAL-ADPD4000Z-PPG PCB设计图(7)

图15. 评估板EVAL-ADPD4000Z-PPG PCB设计图(8)