Dialog Semiconductor DA14681 User manual

User Manual
DA14681 Wearable Development
Kit Hardware Manual
UM-B-077
Abstract
This document describes the hardware design of the DA14681 Wearable Development Kit, which is
based on the Dialog Semiconductor DA14681 Bluetooth® low energy SoC. This wearable module
includes a geomagnetic sensor, an accelerometer, a combined environmental sensor that can sense
temperature, pressure and humidity levels, a heart rate monitor, and NFC functionality. It can display
environmental readings as well as health data such as step count, distance traveled, calories burned
and heart rate. All these functions are combined in a wearable-like watch, enabling the user to
physically wear it and keep a track of his day-to-day activities.

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Contents
Abstract................................................................................................................................................ 1
Contents............................................................................................................................................... 2
Figures.................................................................................................................................................. 2
Tables ................................................................................................................................................... 3
1Terms and Definitions................................................................................................................... 5
2System Overview........................................................................................................................... 6
2.1 Features................................................................................................................................ 6
2.2 Electrical Characteristics....................................................................................................... 6
3Introduction.................................................................................................................................... 6
4DA14681 Reference Design - Motherboard ................................................................................ 9
4.1 DA14681 System.................................................................................................................. 9
4.1.1 Debugging Section .............................................................................................. 10
4.1.2 QSPI Data Flash Memory.................................................................................... 13
4.1.3 Crystal Oscillators................................................................................................ 13
4.1.4 DA14681 Pin Assignment.................................................................................... 14
4.2 GPIO Expander................................................................................................................... 16
4.3 Microphone ......................................................................................................................... 17
4.4 Li-Po Battery ....................................................................................................................... 18
4.5 LCD Display ........................................................................................................................ 20
4.6 DA14681 Wearable Reference Design Sensors ................................................................ 22
4.6.1 BMI160 - Combined Inertial Measurement Unit and Accelerometer................... 22
4.6.2 BMM150 - Magnetometer.................................................................................... 23
4.6.3 BME280 - Environmental Sensor ........................................................................ 24
4.6.4 BH1750FVI –Ambient Light Sensor.................................................................... 24
4.7 RTC –Real Time Clock ...................................................................................................... 25
4.8 Antenna............................................................................................................................... 26
4.9 Heart Rate Monitor (HRM).................................................................................................. 27
4.10 DA14681 Wearable Reference Design- Motherboard Schematics .................................... 29
5DA14681 Reference Design - Daughterboard........................................................................... 32
5.1 Near Field Communication (NFC)....................................................................................... 32
5.2 Capacitive Touch and Proximity Controller......................................................................... 36
6Wearable Reference Design - PCB............................................................................................ 39
7Power Consumption Measurements......................................................................................... 41
8Wearable Reference Design Enclosure .................................................................................... 43
Revision History ................................................................................................................................ 46
Figures
Figure 1: Top Level Block Diagram of the DA14681 Wearable Reference Design .............................. 7
Figure 2: DA14681 Wearable Reference Design Rev.E (Motherboard) - Top view ............................. 8
Figure 3: DA14681 Wearable Reference Design Rev.E (Motherboard) - Bottom view........................ 8
Figure 4: DA14681 System Schematic ................................................................................................. 9
Figure 5: Communication Interface Board (CIB)................................................................................. 10
Figure 6: IDC-10 Cable between Interface Board and Wearable Reference Design Board............... 11
Figure 7: IDC-10 Cable between Interface Board and Wearable Reference Design Enclosure ........ 12

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Figure 8: QSPI Data Flash Schematic ................................................................................................ 13
Figure 9: GPIO Expander Schematic.................................................................................................. 16
Figure 10: SPK0838HT4H Microphone Schematic............................................................................. 17
Figure 11: 3.7 V 190 mAh Li-Po Battery.............................................................................................. 18
Figure 12: Li-Po Battery Charging/Discharging Curves ...................................................................... 19
Figure 13: Technical Characteristics of the 190 mAh Li-Po Battery ................................................... 19
Figure 14: TFT Display External Clock Selection................................................................................ 20
Figure 15: TFT Display Connector Schematic .................................................................................... 20
Figure 16: TFT Display........................................................................................................................ 21
Figure 17: BMI160- Inertial Sensor Schematic.................................................................................... 22
Figure 18: BMM150- Geomagnetic Sensor Schematic....................................................................... 23
Figure 19: BME280- Environmental Sensor Schematic...................................................................... 24
Figure 20: BH1750FVI Ambient Light Sensor Schematic ................................................................... 24
Figure 21: RTC Schematic.................................................................................................................. 25
Figure 22: Ceramic Antenna PCB Footprint and Mechanical Specifications...................................... 26
Figure 23: HRM Schematic ................................................................................................................. 28
Figure 24: DA14681 Wearable Reference Design - BLE SoC, QSPI, GPIO Expander Schematic.... 29
Figure 25: DA14681 Wearable Reference Design - Peripherals Schematic ...................................... 30
Figure 26: DA14681 Wearable Reference Design - Sensors Schematic ........................................... 31
Figure 27: Simplified Block Diagram of the NFC Module.................................................................... 32
Figure 28: NFC Module Schematic..................................................................................................... 33
Figure 29: Block Diagram of the Host Communication Mode Implementation ................................... 34
Figure 30: Voltage Levels of the NFC Module Pins –Host Communication Mode............................. 34
Figure 31: Voltage Levels of the NFC Module Pins –RF Communication Mode............................... 35
Figure 32: Capacitive Touch Controller Schematic............................................................................. 36
Figure 33: Shield Layer Function ........................................................................................................ 36
Figure 34: PCB Touch Pad Recommended Shapes........................................................................... 37
Figure 35: PCB Touch Pad Daughterboard–Top View...................................................................... 37
Figure 36: PCB Touch Pad Daughterboard - Bottom View................................................................. 37
Figure 37: Touch Pad Daughterboard Attached to the Motherboard.................................................. 37
Figure 38: DA14681 Wearable Reference Design - Daughterboard Schematic................................. 38
Figure 39: DA14681 Wearable Reference Design –Motherboard (Top View)................................... 39
Figure 40: DA14681 Wearable Reference Design –Motherboard (Bottom View).............................. 39
Figure 41: DA14681 Wearable Reference Design –Daughterboard (Top View)............................... 40
Figure 42: DA14681 Wearable Reference Design –Daughterboard (Bottom View).......................... 40
Figure 43: Current Measurement Test Points ..................................................................................... 41
Figure 44: Actual Current Consumption Waveform (Sleep Mode) from DC Power Analyzer............. 42
Figure 45: Wearable Reference Design Wnclosure –Exploded View................................................ 43
Figure 46: Wearable Reference Design Enclosure –Side View......................................................... 43
Figure 47: Actual Enclosure –Top View............................................................................................. 44
Figure 48: Actual Enclosure –Bottom View........................................................................................ 44
Figure 49: Wearable Watch Placed on the Left Wrist ......................................................................... 45
Tables
Table 1: DA14681 Wearable Reference Design................................................................................... 6
Table 2: Y1 (16 MHz Crystal) Characteristics ..................................................................................... 13
Table 3: Y2 (32 kHz Crystal) Characteristics ...................................................................................... 14
Table 4: Wearable Reference Design Rev. E Pin Assignment........................................................... 14
Table 5: GPIO Expander Pin Assignment........................................................................................... 16
Table 6: Battery Dimensions ............................................................................................................... 18
Table 7: Recommended Operating Conditions................................................................................... 21
Table 8: Power Consumption.............................................................................................................. 21
Table 9: BMI160 Inertial Sensor - Electrical Characteristics............................................................... 22
Table 10: BMM150 Geomagnetic Sensor - Electrical Characteristics ................................................ 23
Table 11: BME280 Environmental Sensor –Electrical Characteristics .............................................. 24
Table 12: Key Antenna Characteristics............................................................................................... 26
Table 13: Green - IR LED Maximum Ratings...................................................................................... 27

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Table 14: Electrical Characteristics –IR LED ..................................................................................... 27
Table 15: Electrical Characteristics –Green LED............................................................................... 28
Table 16: NFC Module Pin Description (Partial) ................................................................................. 33
Table 17: Current Consumption of Wearable Reference Design Sensors and Peripherals............... 41

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1 Terms and Definitions
APDU Application Protocol Data Unit
BLE Bluetooth low energy
CIB Communication Interface Board
DCR Direct Current Resistance
DCXO Digitally Controlled Crystal Oscillator
HRM Heart Rate Monitor
HW hardware
IF Infrared
IFA Inverted-F Antenna
IoT Internet of Things
JTAG Join Test Action Group (test interface)
LED Light Emitting Diode
LDO Low Drop-Out (regulator)
NFC Near Field Communication
PCBA Printed Circuit Board Assembled
RF Radio Frequency
RTC Real Time Clock
SE Secure Element
SMD Surface Mounted Device
SOC System on Chip
SPI Serial Peripheral Interface
UART Universal Asynchronous Receiver/Transmitter
USB Universal Serial Bus

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2 System Overview
2.1 Features
■Highly integrated Dialog Semiconductor DA14681 Bluetooth® Smart SoC
■Stand-alone module
■High capacity slim size 190 mAh rechargeable LiPo battery
■Low power 80 A (sleep current)
■Low cost PCB touch pads
■Incorporated heart rate monitor
■Environmental sensor for temperature, humidity and air pressure readings
■Combined Gyro/Accelerometer sensor unit
■NFC module for payment applications
■Access to processor via JTAG and UART from the enclosure
■Compact design
■35 mm x 39 mm x 9 mm PCBA
2.2 Electrical Characteristics
Table 1: DA14681 Wearable Reference Design
Parameter
Description
Conditions
Min
Typ
Max
Unit
VBAT
battery supply voltage
3.6
3.8
4.2
V
ISLEEP_TOTAL
average sleep current
conducted; TA= 25 °C
18
A
ICONNECTED
average current when
connected to a host
conducted; TA= 25 °C
550
A
fOPER
operating frequency
2400
2483.5
MHz
PO
RF output power
conducted; VBAT = 3 V;
TA= 25 °C
0
dBm
3 Introduction
Wearable devices are miniature electronic devices worn on the body, often integrated with or
designed to replace an existed accessory, such as a watch. This market segment is currently
booming and is enabled by Internet of Things (IoT) technology. Thus the need for smaller, low power
devices is rapidly increasing. Some of the current trends are smart watches, smart glasses, and
sports and fitness activity tracker equipment. In addition to the consumer market, the medical
industry is creating a demand for such devices that monitor physical conditions and functions.
The DA14681 wearable reference design described in this manual, is a low power and compact
prototype that can easily fit in a suitable enclosure to form a wearable smart watch. The PCB layout
of the wearable reference design is shown in Figure 2 (top view) and Figure 3 (bottom view).
Each subblock of the system is described in sufficient detail to quickly start using it and test the
functionality. Section 7presents the actual power measurements taken and describes the wrist watch
type enclosure.
The top level block diagram of the reference design is illustrated in Figure 1.

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DA14681
BLE
LDR1
10 POS ZIF connector
en
clk
JTAG
UART1
SDO2,CS2,SCK2
Ambient Light
sensor
HRM
Dyna-Image
DI5115
16KHz
XTAL
32KHz
XTAL
BMM150
magneto
BMI160
acc & gyro
BME 280
Temp
Pressure
Humidity
Debugging
connector
NFC
Ifineon
Capacitive
touch
2xIR
LED
GPIO Push
Button
HRM
Discrete
solution
LDR2 2x
GRN
LED
I2C_Bosch
USB
Connector
I2C
BME_nCS
BMI_nCS
UART2
I2C
QSPI
I2C
USBP
USBN
VBUS
I2C
Serial
Interface
GPIO
V18P
V33
V33
V18P
V18
VBAT
V18P
V18P
V18P
V33
V18P
V18P
LiPoly
190mAh
V18
VBAT
3V LDO
V33
1.28" TFT monochrome DISPLAY
32KHz
RTC
Daughterboard
3V_LDO
I2C
V18P
clk
VBAT
V33
VBAT
Vibrator
MIC DP/DM
VBAT
SDO,SDI,
SCK
GPIO
EXPANDER
QSPI
Flash 8Mbit
V18P
Figure 1: Top Level Block Diagram of the DA14681 Wearable Reference Design

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Figure 2: 680-RD-wearable-mb_vE- Top view
Figure 3: 680-RD-wearable-mb_vE- Bottom view
Push
Button
Vibrator
Debugging
port
HRM

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4 DA14681 Reference Design - Motherboard
4.1 DA14681 System
The DA14681 is a flexible Bluetooth®low energy System-on-Chip combining an application
processor, memories, cryptography engine, power management unit, digital and analog peripherals
and a radio transceiver.
The DA14681 is based on an ARM®Cortex®-M0 CPU delivering up to 84 DMIPS and provides a
flexible memory architecture, enabling code execution from embedded memory (RAM, ROM) or non-
volatile memory (OTP or external Quad-SPI Flash memory for DA14681). The advanced power
management unit of the DA14681 enables it to run from primary and secondary batteries, as well as
provide power to external devices.
An on-chip PLL enables on-the-fly tuning of the system clock between 32 kHz and 96 MHz to meet
the high processing requirements.
Figure 4: DA14681 System Schematic
The DA14681 SoC power management subsystem consists of:
VBUS: Battery charger input as well as USB bus voltage. A decoupling capacitor equal or less than
4.7 F is placed close to VBUS pin.
VBAT1: Battery connection. A 1 F decoupling capacitor (C10), is required close to the pin (0402
package, 6.3 V). Voltage range for VBAT1 is 1.7 V to 4.75 V.
VBAT2: Input of the SIMO DC-DC converter. It is shorted externally with VBAT1. A 1 F decoupling
capacitor (C11) is required next to the pin (0402 package, 6.3 V).

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V33: Output voltage rail (3.3 V). A ceramic decoupling capacitor of 4.7 F (C3), (0402 package,
6.3 V) is placed. V33 cannot be turned off.
SIMO DC-DC converter outputs: V18, V18P, V12, V14. The inductor needed for DC-DC operation
is placed externally. A low DCR inductor (L1) of 470 nH, 0805 is connected on LX/ LY pins.
V18, V18P: Power rails (1.8 V) for supplying external devices, even when the system is in sleep
mode. Decoupling ceramic capacitors (C4, C5) of 10 F (0603 package, 16 V), are placed as close
as possible to the V18, V18P pins. V18 is assigned to the external Flash memory. The current
delivery capability of the V18, V18P power rails in active mode is 75 mA, whereas in sleep mode it is
2 mA. When in sleep mode the 1.8 V is supplied directly from the LDO, while in active mode from a
DC-DC converter.
V12: Power rail that supplies the digital core of the DA14681 and delivers up to 50 mA at 1.2 V when
in active mode. A 4.7 F decoupling capacitor (C6) is used (0402 package, 6.3 V).
V14: Power rail that delivers up to 20 mA at 1.4 V and should not be used for supplying external
devices. A 4.7 F decoupling capacitor (C7) is placed close to the V14 pin (0402 package, 6.3 V).
V14_RF: Supply voltage input. It is shorted to V14 on the PCB layout. V14_RF powers the RF
circuits via a number of dedicated internal LDOs. A 4.7 F decoupling capacitor (C8) is placed as
close to the V14_RF pin as possible.
VDDIO: QSPI Flash interface supply voltage. It is connected to the same power rail as the Flash
memory. A 1 F decoupling capacitor (C1) is added. (0402 package, 6.3 V).
4.1.1 Debugging Section
The DA14681 wearable reference design has a dedicated debugging port as shown in Figure 3. Two
debugging ports, JTAG and UART are used on the DA14681 SoC.
The USB-to-JTAG and USB-to-UART functions are implemented by an external Communication
Interface Board (CIB) as shown in Figure 5. This interface board has a SEGGER chip running the
JLink-OB firmware.
Figure 5: Communication Interface Board (CIB)

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The following functions are performed by the interface board:
●Connectivity of PC to the DA14681 JTAG port.
●Connectivity of PC to the DA14681 UART port (full UART is possible but it must be enabled on
the PC driver).
●Hardware RESET capability through the T_RESET signal. Note that the signal T_RESET is
active low and therefore is inverted by U7 before reaching the RST pin on the DA14681.
The following on-board settings have to be enforced in order to be able to program /debug the
wearable reference design board:
Interface board settings (see Figure 5):
●ON-OFF switch set to ON
●USB cable connected at the mini USB connector
●IDC-10 cable from the 1.27 mm pitch header to the target board
Wearable reference design board settings (see Figure 2 and Figure 3):
●IDC-10 cable from interface board is connected at the bottom of the wearable reference design
board (target board).
●ON-OFF switch has to be positioned towards the USB connector in order to be powered by the
communication interface board.
The connection between the interface board and the wearable reference design board (or enclosure)
is shown in Figure 6 and Figure 7.
Figure 6: IDC-10 Cable between Interface Board and Wearable Reference Design Board

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Figure 7: IDC-10 Cable between Interface Board and Wearable Reference Design Enclosure

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4.1.2 QSPI Data Flash Memory
The DA14681 wearable reference design includes an external QSPI Data Flash memory from
Winbond. The W25Q80EW is a 1.8 V, 8 Mbit Flash memory that supports the standard Serial
Peripheral Interface (SPI), Dual/Quad I/O SPI as well as 2-clock instruction cycle Quad Peripheral
Interface (QPI), Serial Clock, Chip Select, Serial Data I/O0 (DI), I/O1(D0), I/O2 (/WP) and
I/O3(/HOLD).
QSPI is supplied from the V18 voltage rail. The same supply voltage is connected to the DA14681
VDDIO pin.
Figure 8: QSPI Data Flash Schematic
The DA14681 uses the external Flash memory for directly executing code with some help from the
internal cache, or simply for mirroring the contents in RAM during booting (option selectable via the
binary image header).
4.1.3 Crystal Oscillators
The DA14681 SoC has two Digitally Controlled Crystal Oscillators (DCXO), one at 16 MHz
(XTAL16M) and a second at 32.768 kHz (XTAL32K). The 32.768 kHz oscillator has no trimming
capabilities and is used as the clock for the Extended/Deep Sleep modes. The 16 MHz oscillator can
be trimmed.
The crystals used on the wearable reference design are specified in Table 2 and Table 3.
Table 2: Y1 (16 MHz Crystal) Characteristics
Reference Designator
Value
Part Number
7M-16.000MEEQ-T
Frequency
16 MHz
Accuracy
±10 ppm
Load Capacitance (CL)
10 pF
Shunt Capacitance (C0)
3 pF

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Reference Designator
Value
Equivalent Series Resistance (ESR)
100 Ω
Drive Level (PD)
50 W
Table 3: Y2 (32 kHz Crystal) Characteristics
Reference Designator
Value
Part Number
ABS07-32.768KHZ-7-T
Frequency
32.768 kHz
Accuracy
±20 ppm
Load Capacitance (CL)
7 pF
Shunt Capacitance (C0)
0.9 pF to 1.2 pF
Equivalent Series Resistance (ESR)
70 kΩ
Drive Level (PD)
0.5 W
4.1.4 DA14681 Pin Assignment
Table 4 shows the pin assignment and related pin names on the aQFN60 package of the DA14681.
Table 4: 680-RD-wearable-mb_vE Pin Assignment
DA14681 AQFN60 Pin Name
Reference Design Signal
Section
P0_0
QSPI_CLK
QSPI data flash
P0_1
QSPI_D0
QSPI data flash
P0_2
QSPI_D1
QSPI data flash
P0_3
QSPI_D2
QSPI data flash
P0_4
QSPI_D3
QSPI data flash
P0_5
QSPI_CS
QSPI data flash
P0_6
SWDIO
Debugging –JTAG
P0_7
PDM_DATA
Microphone
P1_0
HRM_AIN
Heart Rate Monitor
P1_1
USBP
DA14681
P1_2
CAPS_INT
Touch
P1_3
UTX
Debugging –UART
P1_4
SPI2_MOSI
LCD
P1_5
Test point
P1_6
SPI2_CS
LCD
P1_7
SPI2_SCK
LCD
P2_0
XTAL32kp
DA14681
P2_1
XTAL32kn
DA14681
P2_2
USBM
DA14681
P2_3
URX/BUTTON
P2_4
SWCLK
DA14681
P3_0
SPI_MOSI
Sensors

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DA14681 AQFN60 Pin Name
Reference Design Signal
Section
P3_1
SPI_MISO
Sensors
P3_2
SPI_SCK
Sensors
P3_3
BMI_nCS
Sensors
P3_4
BME_nCS
Sensors
P3_5
7816CLK
NFC
P3_6
BMI_INT
Sensors
P3_7
VDDSE
NFC
P4_0
7816IO (URX side)
NFC
P4_1
VIB_EN
Vibrator
P4_2
RTC_IRQ
RTC
P4_3
7816IO (UTX side)
NFC
P4_4
HRM_INT
Heart Rate Monitor
P4_5
PDM_CLK
Microphone
P4_6
SDA
Sensors/HRM/RTC/Touch
P4_7
SCL
Sensors/HRM/RTC/Touch
LED1
LED1
Optional enable to vibrator motor
LED2
LED2
Heart Rate Monitor
LED3
LED3
Heart Rate Monitor

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4.2 GPIO Expander
Due to the high GPIO demand in this reference design a GPIO expander was necessary. The
component used is the low power I2C controlled FXL6408UMX from Fairchild. It uses both power
rails of 1.8 V and 3.3 V while its power consumption remains very low at only 1.5 A (Sleep current).
Table 5: GPIO Expander Pin Assignment
GPIO Expander
Pin Name
Section
P0
Test point
P1
Test point
P2
MIC_EN
Microphone
P3
TFT_EN
LCD
P4
HRM_EN
Heart Rate Monitor
P5
NFC_EN(3V Ldo)
NFC
P6
ENVDDSE
NFC
P7
7816RST
NFC
Driving signals (I2C) are supplied from the 1.8 V rail whereas the output signals are driven from the
3.3 V voltage rail.
Figure 9: GPIO Expander Schematic

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4.3 Microphone
The SPK0838HT4H-B from Knowles is a miniature, high performance, low power, top port silicon
digital microphone with a single-bit PDM output. In this reference design the microphone’s data
signal is driven by the GPIO P0_7 from the DA14681 SoC. Its power consumption during sleep is
only 4.6 A.
The microphone is supplied from an output pin (GPIO2) of the GPIO expander. In this way, the user
can turn off the microphone completely when it is not used. Default state for the microphone is OFF.
Figure 10: SPK0838HT4H Microphone Schematic

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4.4 Li-Po Battery
The battery used is a rechargeable Li-Po from HHS, which is available with capacities of 190 mAh
and 250 mAh. Table 6 shows the battery dimensions.
Table 6: Battery Dimensions
Capacity (mAh)
Dimensions (mm)
Thickness (mm)
190
30 x 30
3.2
250
30 x 30
3.7
The actual Li-Po battery rechargeable battery can be seen in Figure 11:
Figure 11: 3.7 V 190 mAh Li-Po Battery
The charging and discharging curves of the 190 mAh battery are illustrated in Figure 12.

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Figure 12: Li-Po Battery Charging/Discharging Curves
Figure 13: Technical Characteristics of the 190 mAh Li-Po Battery
The LiPo battery discussed is equipped with a protection circuit module (PCM). The PCM will
generally provide the battery with overcharge/discharge protection, short circuit protection, current
limitation, and voltage and current balancing in each cell. All of these factors are important in
obtaining the maximum output and longest operating life from a rechargeable lithium battery.

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4.5 LCD Display
The LCD display selected is a 1.28 inch, 128 x 128 resolution monochrome HR-TFT transflective
panel (LS013B7DH03 from Sharp). The most significant advantage of this display is that it does not
require an external controller. This is due to the fact that each pixel forms a 1-bit write-only memory.
This feature minimizes the processor resources used as there are no continuous data transfers to
refresh the image; the image needs to be written just once.
Figure 14: TFT Display External Clock Selection
The alternating signal needed to prevent any DC bias from building up inside the display is supplied
by an external clock signal generated by a Real Time Clock module (see section 4.7).
Figure 15 illustrates the TFT display connectivity necessary to implement the external clock
functionality. The clock frequency in this case is set to 64 Hz and it is fed into the display via the
RTC_SQW pin of the RTC module. By default this clock is provided by the RTC, alternatively it can
also be supplied by the DA14681 SoC.
Figure 15: TFT Display Connector Schematic