Multi-Rail, Low-IQ Power Reference Design for Wearable ...L2 = 10 H m C OUT2 4.7 Fm C 10 IN mF TPS62770 GND1 DC-DC 2 Step-Up converter EN1 SW1 VO1 L1 = 2.2 H m C 4.7 F OUT1 m VOUT1

TPS62770 Low IQ Buck and Boost

Converter

Wireless MCU

PMOLED

VBatt

Communication

Power

Bluetooth�SMART

Copyright © 2016, Texas Instruments Incorporated

1TIDUBN9–April 2016Submit Documentation Feedback


Multi-Rail, Low-IQ Power Reference Design for Wearable Applications

TI DesignsMulti-Rail, Low-IQ Power Reference Design for WearableApplications

Design OverviewWearable applications such as smart wristbands usetwo main power rails to supply the wireless MCU,sensors, and display. The design of these devices istiny and therefore requires the smallest solution sizepossible. This reference design offers a completewearable solution based on the TPS62770 multi-railDC-DC converter including the CC2650 and PMOLEDdisplay.

Design Resources

PMP9792 Design FolderTPS62770 Product FolderCC2650 Product Folder

ASK Our E2E Experts

Design Features• TPS62770: Fully Adjustable VOUT

– Buck Conversion From 1 V to 3 V– Boost Conversion up to 15 V

• Optimized Battery Lifetime From Ultra-Low IQ

• Bluetooth Smart Interface for SmartphoneInteraction

• Visualization Through PMOLED

Featured Applications• Smart Wristbands• Smart Watch• Wireless Sensor• Wearable Electronics

An IMPORTANT NOTICE at the end of this TI reference design addresses authorized use, intellectual property matters and otherimportant disclaimers and information.

http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=TIDUBN9

http://www.ti.com/tool/pmp9792

http://www.ti.com/product/tps62770

http://www.ti.com/product/CC2650

http://e2e.ti.com

http://e2e.ti.com/support/applications/ti_designs/

CC2650

DD-12864WE-4A DISPLAY

Reset DC CS SCK SDINTPS62770

Boost out

Load out

Buck out+1.9 V

Boost EN

Load EN

+1.9-V Load

+9 V+2.5 V to +5.5 V


Key System Specifications www.ti.com

2 TIDUBN9–April 2016Submit Documentation Feedback



1 Key System SpecificationsThe PMP9792 TI Design features the following devices:• TPS62770• CC2650• 128x64-pixel screen DD-12864WE-4A

2 System DescriptionThe PMP9792 has been designed for wearable applications with small displays and low powerconsumption. This subsection addresses the main design elements, such as the power management,wireless microcontroller (MCU), and display.

3 Block DiagramFigure 1 shows a detailed block diagram of the PMP9792 TI Design. The red lines show the powerconnections and the blue lines represent control signals. The input voltage (established either by USBplug or pin contact) connects to the TPS62770 device, which supplies the display and the CC2650 device.

The wireless MCU controls the display and sends the data to be displayed. The MCU controls the DC-DCconverter, as well.

Figure 1. PMP9792 Block Diagram

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SW2

VIN

EN2/PWMVO2

L2 = 10 Hm

COUT2

4.7 Fm

C

10IN

mF

TPS62770

GND1

DC-DC 2Step-Up converter

EN1

SW1

VO1

L1 = 2.2 Hm

C

4.7 FOUT1

m

VOUT1 = 2 V

DC-DC 1360 nA

Step-Down Converter

IQ

CTRLLOAD

Load Output = 2 V

Load Switch

GND2

VSEL1

VSEL2

VSEL3

BM

ON/OFF

MCU / BLE

Sensors

FB

VOUT2 = 12 V

PMOLED


www.ti.com Block Diagram




3.1 Highlighted Products

3.1.1 TPS62770The TPS62770 is a tiny power solution for wearable applications (see Figure 2). The device includes a360-nA ultra-low IQ step-down converter, a slew-rate-controlled load switch, and a dual-mode boostconverter. The output voltage of the step down converter can be selected with three VSEL between 1.0 V,1.05 V, 1.1 V, 1.2 V, 1.8 V, 1.9 V, 2.0 V, and 3.0 V. The output voltage can be changed during operation.In shutdown mode, the output of the step down converter is pulled to GND. The integrated load switch isinternally connected to the output of the step down converter and features slew rate control during theturnon phase. After turning off, the output of the load switch connects to GND.

The dual-mode boost converter can generate a constant output voltage up to 15 V for applications such asa passive-matrix organic light-emitting diode (PMOLED) supply or a constant output current, which is usedin LED back light supplies. The output voltage can be adjusted up to 15 V with external resistors or set toa fixed 12 V by connecting the FB pin to VIN. The device features an internal overvoltage protection of17 V in case the FB node has been left open or tight to GND. The TPS62770 also includes an internalrectifier and load disconnect function. When used as a constant output current driver, the device offers apulse width modulation (PWM) to analog converter to scale down the reference voltage according to theduty cycle of the PWM signal.

The device is available in a small 16-pin, 0.4-mm pitch WCSP package.

Figure 2. TPS62770 Internal Block Diagram

http://www.ti.com


Block Diagram www.ti.com




3.1.2 CC2650The CC2650 is a wireless MCU targeting Bluetooth Smart, ZigBee® and 6LoWPAN, and ZigBee RF4CEremote control applications (see Figure 3).

The device is a member of the CC26xx family of cost-effective, ultra-low power, 2.4-GHz radio frequency(RF) devices. A very-low, active RF and MCU current and low-power mode current consumption providesexcellent battery lifetime and allows operation on small coin cell batteries and in energy-harvestingapplications.

The CC2650 contains a 32-bit ARM® Cortex®-M3 running at 48-MHz as the main processor and a richperipheral feature set, including a unique ultra-low power sensor controller, which is ideal for interfacingexternal sensors or collecting analog and digital data autonomously while the rest of the system is in sleepmode.

These features make the CC2650 ideal for applications within a whole range of products includingindustrial, consumer electronics, and medical.

The Bluetooth® low energy controller and the IEEE 802.15.4 MAC are embedded into ROM and partly runon a separate ARM® Cortex®-M0 processor. This architecture improves overall system performance andpower consumption and frees up flash memory for the application. The Bluetooth Smart and ZigBeestacks are available free of charge from www.ti.com.

Figure 3. CC2650 Internal Block Diagram

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http://www.ti.com

www.ti.com Block Diagram




3.1.3 Densitron Display DD-12864WE-4AThe DD-12864WE-4A display from Densitron Technologies is a 128x64-pixel PMOLED display (seeFigure 4). The overall dimensions are 26.70 mm × 19.26 mm × 1.45 mm. The screen uses an integratedSSD1306 driver.

Figure 4. PMOLED Display Image

The display enables different types of communications like 68xx-series microprocessor (MPU) parallelinterface, 8080 series MPU parallel interface, serial peripheral interface (SPI) with three or four wires, andI²C. The application for this design uses the four-wire SPI communication between the display andCC2650 device.

The display is a bicolor display, which means that the color is white when a pixel is on and the color isblack when a pixel is off.

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USB for power supply

JTAG connector

Connector for power supply 2.5 V to 5.5 V

Boost and load switch enable

Buck output voltage setting-Settable from 1 V to 3 V(currently set at 1.9 V)

CC2650 wireless (BLE) MCU

PMOLED screen-Screen voltage = 9 V-Logic voltage = 1.9 V

TPS62770 power stage

Push button

Crystals

External antenna footprint

PCB antenna

CC2650 is advertising CC2650 is connected

Display a screen from a series of 3 screens

2.5

Advertise data2.5

Display the connection screen

Wait for BLE data

Number received

Text received

Pics number

Button pressed

Display number

Display text

Display picture

Senddata


Software Architecture www.ti.com




4 Software ArchitectureThe PMP9792 TI Design uses a loaded firmware for testing and demonstration purposes. Figure 5 showsthe functionality of the firmware.

Figure 5. Software Functional Chart

5 Getting Started HardwareThis section provides an overview of the PCB with the applicable settings through jumpers.

5.1 Hardware Overview

Figure 6. PMP9792 Overview

http://www.ti.com


www.ti.com Getting Started Hardware




5.2 Multi-Rail Power SolutionThe power solution occupies a very small footprint on the PCB because of the tiny 16-pin, 1.62×1.62-mmWCSP package (0.4-mm pitch) and the required passive components (see Figure 7).

Figure 7. TPS62770 Device Pinout and Layout

5.3 Voltage SettingThe board enables the option to set the buck output voltage through the J3, J4, and J5 jumpers (seeFigure 8). The user can then choose the CC2650 voltage by moving these three jumpers. The initialconfiguration of the buck output voltage has been set to 1.8 V.

The board also has an option to force the enable for the boost (EN2, J7) and the enable for the loadswitch (CTRL, J6) by setting the jumpers to logic 1. The user also has the option to put the jumpers on theMCU setting, after which the user may set the enable pins directly from the CC2650 device.

Figure 8. VSEL Jumper Image

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Getting Started Hardware www.ti.com




Table 1 lists the jumper positions required to set the buck output voltage. The recommended supply forVDDS and VDDR is 1.7 V to 1.95 V.

Table 1. Buck Converter Output Voltage by Jumper Settings

VBUCK_OUT (V) VSEL3 (J5) VSEL2 (J4) VSEL1 (J3)1 0 0 0

1.05 0 0 11.1 0 1 01.2 0 1 11.8 1 0 01.9 1 0 12 1 1 03* 1 1 1

Table 2. Color Mapping For Table 1

Recommended values of the buck output voltage for the CC2650.Not recommend values of the buck output voltage for the CC2650.Does not cause damage but the CC2650 does not work.Do not use this voltage per risk of destroying the CC2650.

CAUTIONThe absolute maximum voltage for VDDS and VDDR for the CC2650 device is2.25 V.

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Input Voltage (V)

Cur

rent

(m

A)

0 1 2 3 4 5 60

5

10

15

20

25

30

35

40

45

50Input Current (mA)Buck Out (mA)Boost Out (mA)

www.ti.com Test Data and Measurements




6 Test Data and MeasurementsThis section shows several measurements from the PMP9792 board. The following subsection providesDC measurements that show the overall current consumption. Section 6.2 shows the behavior of thedisplay and the boost converter output during display refreshment for several pictures.

6.1 DC Current MeasurementsIn this measurement, the system is in advertising mode and displays the welcome screen (see Figure 9).The system is supplied with an adjustable DC voltage and the input current is measured. The boost outputis at 9 V (display supply) while the buck output is set to 1.8 V (CC2650 supply).

The blue curve shows the overall current consumption at the input of the TPS62770 device. The greencurve represents the boost converter output current, which supplies the PMOLED display. The red traceshows the buck converter output current, which powers the CC2650 in advertising mode.

Figure 9. Current Consumption Measurements

http://www.ti.com


Screen half-white, half-black horizontally Screen half-white, half-black vertically Screen half-white, half-black diagonally

Test Data and Measurements www.ti.com




6.2 Display MeasurementsThe following measurements in Figure 10 show the boost converter output voltage and current. The dynamic current consumption varies over timeand depends on the picture that the display is currently showing.

The blue trace shows the AC behavior (9-V DC offset) of the boost converter output as a reaction to the dynamic current change. The magentatrace shows the current consumption of the display.

Figure 10. Supply Measurements—Dynamic PMOLED Display

http://www.ti.com


www.ti.com Design Files




7 Design Files

7.1 SchematicsTo download the schematics, see the design files at PMP9792.

7.2 Bill of MaterialsTo download the bill of materials (BOM), see the design files at PMP9792.

7.3 Layout PrintsTo download the layer plots, see the design files at PMP9792.

7.4 Altium ProjectTo download the Altium project files, see the design files at PMP9792.

7.5 Gerber FilesTo download the Gerber files, see the design files at PMP9792.

7.6 Assembly DrawingsTo download the assembly drawings, see the design files at PMP9792.

8 Software FilesTo download the software files, see the design files at PMP9792.

9 References

1. Texas Instruments, CC2650 SimpleLink™ Multistandard Wireless MCU,CC2650 Datasheet (SWRS158)

2. Texas Instruments, TPS62770 Multi-Rail DC/DC Converter For Wearable Applications,TPS62770 Datasheet (SLVSCX0)

10 About the AuthorAYMERIC NICOLAS works as an Analog Field Application Engineer for Texas Instruments France. As agraduate engineer, he has undertaken a project with ALPS for 6 months to improve his knowledge inpower management. At the end of 2016, Aymeric will be deployed in Paris, where he will join the salesorganization. Aymeric received his Engineering Degree in embedded systems in 2015.

FLORIAN FECKL works as an Analog Power Application Engineer for the Texas Instruments ALPSGroup. In this role, he is part of the development team, holds trainings, supports worldwide customers,and develops reference designs. Since 2013 his focus has been on ultra-low power applications. Florianreceived his master of engineering (embedded systems) in 2012.

http://www.ti.com









http://www.ti.com/lit/pdf/SWRS158

http://www.ti.com/lit/pdf/SLVSCX0

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Documents

Multi-Rail, Low-IQ Power Reference Design for Wearable ...L2 = 10 H m C OUT2 4.7 Fm C 10 IN mF TPS62770 GND1 DC-DC 2 Step-Up converter EN1 SW1 VO1 L1 = 2.2 H m C 4.7 F OUT1 m VOUT1