ADPD1081 datasheet(31/74 Pages) AD

31 / 74 page

Data Sheet

ADPD1080/ADPD1081

Rev. C | Page 31 of 74

APPLICATIONS INFORMATION

TYPICAL CONNECTION DIAGRAM

Figure 36 shows a typical circuit used for wrist-based heart rate

measurement with the ADPD1080 WLCSP using a green LED.

The 1.8 V I2C communication lines, SCL and SDA, along with

the GPIO0 and GPIO1 lines, connect to a system microprocessor

or sensor hub. The I2C signals can have pull-up resistors connected

to a 1.8 V or a 3.3 V power supply. The GPIO0 and GPIO1 signals

are only compatible with a 1.8 V supply and may need a level

translator. The circuit shown in Figure 36 is identical for the

ADPD1081, except the I2C interface is replaced by an SPI.

There are multiple ways to connect photodiodes to the 8-channel

ADPD1080 LFCSP, as shown in Table 22 and Figure 39. The

photodiode anodes are connected to the PD1 to PD8 input pins

and the photodiode cathodes are connected to the cathode pin,

PDC.

Provide the 1.8 V supply, VDD, to AVDD and DVDD. The LED

supply uses a standard regulator circuit according to the peak

current requirements specified in Table 3 and calculated in the

LED Driver Pins and LED Supply Voltage section.

For best noise performance, connect AGND, DGND, and

LGND together at a large conductive surface, such as a ground

plane, a ground pour, or a large ground trace.

The number of photodiodes or LEDs used varies depending on

the application as well as the dynamic range and SNR required.

For example, when using a single, large photodiode in an

application, split the current between multiple inputs to increase

the dynamic range. By connecting the anode of the photodiode

to multiple channels, the current can split evenly among the

number of channels connected, effectively increasing the dynamic

range over a single channel configuration. Alternatively, in

situations where the photodiode is small or the signal is greatly

attenuated, SNR can be maximized by connecting the anode of

the photodiode to a single channel. It is important to leave the

unused input floating for proper device operation.

Figure 37 and Figure 38 show the recommended connection

diagram and printed circuit board (PCB) layout for the 16-ball

WLCSP ADPD1080 and 17-ball WLCSP ADPD1081, respectively.

The current input pins, PD1 and PD5, have a typical voltage of

1.3 V during the sampling period. During the sleep period,

these pins are connected to the cathode pin. The cathode and

anode voltages are listed in Table 3.

PD5

PDC

PD1

LEDX1

VLED

VREF

1µF

AGND

DGND

LGND

0.1µF

DVDD

AVDD

1.8V

10kΩ 10kΩ

1.8V

SCL

SDA

GPIO0

GPIO1

TO DIGITAL

INTERFACE

ADPD1080

4.7µF

Figure 36. Typical Wrist-Based HRM Measurement

LGND

LEDX2

LEDX3

LEDX1

SDA

SCL

GPIO0

DVDD

DGND

GPIO1

VREF

AVDD

PD5

PDC

PD1

AGND

Figure 37. ADPD1080 Connection and PCB Layout Diagram (Top View),

16-Ball WLCSP

LGND

LEDX2

LEDX3

LEDX1

GPIO0

GPIO1

MISO

DGND

MOSI

AVDD

AGND

VREF

PD5

PDC

PD1

SCLK

Figure 38. ADPD1081 Connection and PCB Layout Diagram, Dashed Line

Traces from Blind Vias (Top View), 16-Ball WLCSP

ADPD1081 Datasheet(PDF) 31 Page - Analog Devices

ADPD1081 Datasheet(HTML) 31 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

Datasheet Download

Link URL