“WalletPhone”

ZTE CSX

Concept Submission

Blake Willis (funkboy at gmail dot com)

2016-09

https://community.zteusa.com/ideas/2018

Project Drivers

My favorite phone ever: Nokia 8210 (circa 2000)

• Always worked, simple, never needed upgrades
• Battery lasted forever (almost a week)
• Drop it down the stairs, doesn’t care
• Impressive ergonomics
• Tetherable modem for laptop Internet access
• 79g, 102x45x18mm: fits in jeans’ watch pocket, don’t even know it’s there until it rings

16 years later, nothing on the market comes close...

What do I carry these days?

Samsung B2710:

• IP67 water/dust/shockproof, lanyard loop
• Powerful flashlight with dedicated button
• Battery lasts forever (almost a week)
• Good Bluetooth/3G tethering
• Simple UI, Google Maps/Opera Mini
• Severely limited by keyboard/screen

Nexus 7 LTE:

• Just small enough to fit pants/coat pocket
• Much more productive than smartphone
• Talk on B2710, work on Nexus 7

But that sounds pretty clunky...

Yep, it’s a compromise.

With clear advantages & disadvantages.

So I came up with the “WalletPhone” concept.

What is the “WalletPhone” Concept?

An Android LTE smartphone:

• Exactly the size of a stack of credit cards
• With good battery life
• Good durability
• Practical features e.g. powerful flashlight, lanyard loop
• “Digital Presence Anchor”: act as connectivity & storage server for other (bigger) devices

“WalletPhone”

Core Concepts

What Makes “WalletPhone” Different?

Adaptations to living in a wallet most of the time:

• Advanced haptic feedback system (LRA/DRV2605L)
• Latest Bluetooth stack, Bluetooth LE
• Triple-standard wireless charging (A4WP/Qi/PMA)
• NFC: pairing, data transfer & payments [maybe...]
• Specific ringtones designed to be heard from inside a handbag…
• Unconventional layout, tiny low-power components (more a scaled-up LTE smartwatch than a scaled-down mobile phone)

But it must also be a very good phone when not in a wallet!

What Makes “WalletPhone” Different?

Advanced Haptic Feedback System

• Precision Microdrives C08-001 Linear Resonant Actuator (3.3x8mm cylinder)
• Somewhat like a loudspeaker, w/weight instead of cone
• TI DRV2605L haptic driver chip, ~100 pre-baked signals, also wave I/O (incl. audio)
• LRA taped to phone back & two sides: max chassis contact, doesn't vibrate PCB
• 1.4G max vibration: 2-3x more vs. typical motor, more reactive start/stop too
• 1.8v, ~50mA: 3x better Gs/watt vs. typical motor

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What Makes “WalletPhone” Different?

What do we do with our linear resonant actuator?

• Powerful vibration, can feel in handbag/wallet
• Use LRA as subwoofer to enhance audio playback
• During development, record vibrations & sounds from real devices
• Buttons, sliders, camera shutters, anything else (bad washer/dryer, firecracker, etc...)
• We realistically simulate tactile feedback & sound from button clicks, so
• We use bezel touch actions & haptic feedback instead of physical buttons!
• Phone only has a power/wake button
• Lower component count & cost
• Simplify frame design, reduce dust/moisture ingress points
• Certainly other interesting applications...

What Makes “WalletPhone” Different?

Only one tiny camera

• Cameras are big & require big holes in frame; simply no room for more
• Single small/cheap camera helps keep costs down too
• Sony IMX208 probably best one that will fit: 4.3x2.8x2.8mm
• Back-illuminated 2.1MP Exmor-R CMOS, 1.4μm pixels, decent low light performance
• Low MP = low power draw, processing power, & storage requirements
• You don’t need more than 2MP for social media anyway :-)
• RAW output available, max control over HDR & JPEG compression for good quality
• Can record full HD video, max 60fps
• Includes ambient light sensor functionality
• f/1.9 28mm equivalent lens
• Would prefer to use Omnivision 2 or 4mp camera w/bigger pixels, if it’ll fit...

What Makes “WalletPhone” Different?

Unique camera mount position/angle

• Camera mounted in middle of right side of chassis
• Entire stainless steel right side panel canted forward at ~20°
• Camera pointed forward towards subject when holding phone in natural position
• Allows for very inconspicuous photos...
• Touch "shutter" on screen bezel, get haptic response:
• Vibration + audio from real SLR camera shutter/mirror
• ~20° forward angle + 28mm wide-angle lens + near 180° AMOLED viewing angle =
• Can use as makeshift videoconference/selfie cam too
• Not great, but a lot better than nothing
• Coordinate ALS data w/VL6180X proximity sensor
• w/microphone data: figure out when we’re in a wallet

What Makes “WalletPhone” Different?

Powerful flashlight/camera flash

• Cree XQ-E R2 high intensity neutral white LED: 1.6x1.6x0.9mm
• Mounted at top of ~20° stainless “camera-side” panel
• Still visible when phone is in most wallet slots; useful without removing from wallet
• ~25mm separation between camera & flash reduces redeye & lens flare
• LED color = tradeoff vs. thermal efficiency, need photographic testing to get it right
• Ultra-efficient LED: dT @2W/200lm is only 12C; don’t need to get hot to get bright
• Dynamically control LED power as part of global system thermal management
• USB cage, aluminium SIM tray, & rough-brushed frame become part of heat sink
• Other use: high frequency strobe as threat deterrent
• Cheap ~1W alternative: OSRAM PSLR32

“WalletPhone” Design Process

“WalletPhone” Design Process

Thickest card stack that fits in most wallets’ main slots: 85.6x54x~6mm (6 credit cards)

• Iterate design using production devices/components
• Combination of scaled-down phone & scaled-up watch
• ZTE Nubia My Prague thinner than card stack: 5.5mm
• w/3.5mm thick 2200mAh LiPo battery, AMOLED display
• So, everything excluding battery == 2mm
• Same non-battery thickness as many other thin phones
• LTE smartwatch teardowns provide design insight & component selection hints

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“WalletPhone” Design Process

Iterate to get close to 85.6x54x~6mm:

• Can go a tiny bit wider (top edge protrudes from credit card slot)
• ZTE Nubia Z9 NX511J LiPo battery energy density = ~650 Wh/L
• 70x51x4.0mm 650 Wh/L LiPo battery = 2450mAh
• 70x51x3.86mm 650 Wh/L LiPo same height as NX511J=2360mAh
• Estimate Gorilla Glass SR + AMOLED + rear panel = 2.0mm thick
• Target exterior dimensions: 86.2x~57.6x~6mm
• Not “world’s thinnest phone”; care about fitting credit card slot
• Can go a tiny bit thicker (e.g. ~0.4mm) if necessary

Space remaining for most components: 57x15x~4mm

• Enough height for two 0.4mm PCBs w/<0.7mm components
• No large camera modules like typical smartphone

“WalletPhone” Design Process

Think of it like a more-powerful scaled-up LTE smartwatch

• 57x15x~4.0mm: much bigger than LTE smartwatch mainboard
• Example: LG Watch Urbane LTE 2nd Edition ==
• 44.5mm diameter, 14.2mm thick (incl. 570mAh battery)
• Typical 40mm watch PCB surface area (both sides): ~25cm2
• WalletPhone has much more space for everything
• WalletPhone PCB surface area: left/right “side channels” = ~3cm2 each
• Double-sided “rear” & “front” (primary) PCBs = ~16cm2 each
• Total PCB surface area = ~38cm2
• Watch accessory chips are smallest/lowest-power components available
• Add camera, light, more/better antennas, >4x bigger battery vs. LG watch
• Wearable-specific Gorilla Glass SR+ tougher than GG4/5
• Stainless steel watches look fantastic, 3x stronger/stiffer than aluminium too

Display Selection

Original concept called for E-Ink

• Very low power consumption, durable
• E-Ink Carta 4th-gen grayscale looks great, 300+DPI
• Needs external backlighting (but can be pretty thin)
• Used on Sony SWR30 watch, ~3.3mm side bezels
• However, Triton color options are ~200DPI
• Color E-Ink “white” more like gray, very low contrast
• Real killer: both are 1.2mm thick w/o touchscreen
• Touch digitizer adds another ~0.7mm
• Display stack w/Gorilla Glass = 2.3mm thick…
• Other low-power display technologies? Mirasol, etc.
• All are pricey or not in production

Display Selection

Samsung SM-G9198 & W2016 flip phones use 3.9” touch AMOLED

• Current production (Q3 2016)
• Fits two AMOLED on-cell touch displays + PCB in <5mm thick
• Perfect size: 85x51mm visible
• Looks great: 768x1280, 383DPI (oddball resolution though)
• Assume 1mm thick panel + backing to be on the safe side
• Add 0.4mm Gorilla Glass SR+ or 4/5 (entire phone front panel)
• AMOLED power draw not too bad (w/black background...)
• Doesn’t need space for backlight
• Older 3.7" unit exists: 480x800 (252DPI), 81x49mm
• Older unit not as nice, unsure if still in production

Display Evolution

Green PHOLED-based plastic OLED displays

• Promised by LG Display in 1H 2017
• More power efficient
• Thinner (<0.6mm), bendable
• Touch sensor integrated on-cell
• Uncertain if 3.9” displays will be produced with this tech
• Datasheets/roadmaps only available to customers...

In-cell TDDI IPS thin LCD also interesting, if power-efficient

• Less expensive than AMOLED
• Need space for backlight…

Display Implementation

ZTE already has plenty of experience with post-bezel-era phones

• Nubia Z9, Z11 & My Prague look great
• Unique features on Z-series (“Frame Interactive Technology”)

“WalletPhone” concept display requirements:

• 1280x768 slightly more than 720p, may be complicated to drive
• ~0.5mm on “camera side” edge to route ribbon to TDDI underneath
• Opposite “short edge” bezel is ~0.1mm
• Long edge bezels are 3mm

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Computing Component Selection

Goals:

• Low power consumption/thermal envelope
• Fluid Android Nougat experience (min. 2GB DRAM/16GB flash)
• Must work with all other components (drive display, etc.)
• Keep costs & component count/size to a minimum

What I really want: ARM Cortex A35-based SOC

• Preferably, one ultra-low-power “baseband” core
• + 3 or 4 powerful “compute” cores
• A35 currently only announced in MT Helio X30: massive overkill
• Closest current SOCs are Snapdragon 625/Helio P20:
• Fast ~2ghz A53, low-current thanks to 16nm/14nm LPP FinFET
• Hopefully we’ll see 16/14/10nm A35 SOCs in 1H 2017...

Computing Component Selection

Current LTE smartwatch chips are wimpy low-res 32-bit A7, So we design around 4xA53 now & hope for 4/5xA35 in 2017.

• Require LTE worldband Cat-4; prefer Cat-6 or Cat-4 CA
• Mediatek MT6737/MT6738 or Snapdragon 412/425?
• MT6738: only quad-core full-HD SOC with LTE Cat-6
• Snapdragon 425 has Cat-4 CA (also 802.11ac WiFi)
• Snapdragon 425 drives our display too (max 800x1280)
• No public power draw/thermal data for these two chips
• Battery life/thermals more important than SOC cost
• MT 28nm SOCs are huge! MT6735 = 12.6x12.6x.9mm
• Design around SD425, mount as PoP underneath e-MMC
• Powerful 1.4ghz (underclock for current draw/TDP?)
• If possible, underclock one “baseband” core (or variable clock…)

Computing Component Selection

Micron MT29TZZZ5D6YKFAH-125 W.96N

• e-MMC 5.1 w/2GB LPDDR3 + 16GB NAND in one chip
• Only Micron low-voltage (1.8v) e-MMC 5.1 multichip package
• Measures 11.5x13x0.5mm (nice & thin)
• Many tiny devices mount Snapdragon4xx SOC directly underneath
• Probably other options out there, but
• Micron is nice enough to provide basic data to non-customers
• Hopefully bigger 1.8v packages coming in 1H 2017 (e.g. 3/16)
• Impressively long & complicated part number :-)

SD425 SOC + 16GB/2GB e-MMC = performance like ZTE Blade A512

Computing Component Evolution

What would ideally be in this thing in mid-2017?

• ~2ghz 16/14/10nm 4+1 (“baseband”) core A35 LTE CA SOC
• (Might have to settle for Snapdragon 625/Helio P20...)
• 3GB LPDDR4X + 16GB NAND low-voltage multichip package
• Thinner low-power green PHOLED-based plastic on/in-cell touch display
• Bluetooth 5, 802.11ah WiFi-HaLow &/or 802.15.4 6LoWPAN
• Si-NMC lipo battery w/energy density >650Wh/L (Panasonic NCR18650GA=693Wh/L)
• Even tougher watch-grade Gorilla Glass?

Antenna Component Selection

Antenova “flexiiANT” primary antennas

• <0.2mm thick LTE-optimized antenna <85mm
• “Zhengi” SRFC015 LTE, “Amoris” SRF2W021 WiFi
• Excellent performance, very efficient antennas
• Better antennas = less radio power = more battery life
• Expensive :-( plenty of other options, e.g. Molex )

Molex “flex” diversity/secondary/GPS antennas

• 146185 for LTE, 146186 for WiFi, 146186 for GPS
• 0.1mm thick
• Provide some additional diversity vs. two identical antennas
• Much cheaper than Antenova; helps keep costs down
• If 146185 performance as good as Zhengi, could replace primary LTE too

Could potentially use stainless frame as high-Z antenna, but certainly not <100ohm...

Wireless Charging in your Wallet

MT3188 triple-standard wireless power receiver chip & coil

• PMA & Qi & A4WP; Oh My!
• Once again, “budget” MediaTek provides data others hide
• http://tinyurl.com/josq9yw explains everything you need
• Use MediaTek dual-freq. coil reference design for now
• Coil measures ~65x50mm, .2mm thick
• Can we etch this directly onto the back of display PCB?
• A4WP: flexible placement, ~2cm better range vs. PMA/Qi
• A4WP: easier to use but slower to charge
• Less of an issue here than on devices with huge batteries

Optional accessory: credit-card sized USB powerpack

• http://travelcardcharger.com/ already took care of this one for us...

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NFC: Wireless Payment

This should provide some indication as to how little desire I have to burn design cycles to potentially give someone the ability to steal my money with a radio.

However, “The Market” demands it, so assume:

• Chip is low-power, tiny/thin, & cheap
• PCB/chassis space available to fit chip/coil
• NFC radio & antenna coil don’t affect wireless charging/LTE/WiFi/BT/GPS at all

If any of these requirements aren’t met, dump it.

• Moving right along...

“WalletPhone” Build Process

Materials Selection

• Can be drawn much thinner than aluminium, still stiffer
• Modern stainless alloys stronger than titanium, & much cheaper & easier to work
• Example: Reynolds 953 bicycle tubing walls = 0.3mm thick
• Looks fantastic

• "Free cutting" austenitic alloys add copper to reduce hardness: work with standard tooling
• Specific alloy standard selected: AMS SUS303Cu http://tinyurl.com/jp7ymc5
• Basically, common 304 standard stainless alloy w/copper added
• #3 standard rough brushed surface finish: better thermal diffusivity, grippier surface
• Copper also increases thermal conductivity for use as heatsink (should be >40 W/(m·K))
• Non-ferritic steel: less RF interference, doesn’t demagnetize credit cards :-)

If stainless really doesn’t work, 7068 aluminium is almost as strong as steel, but still only ⅓ as stiff

Frame: Stainless Steel is Real.

Materials: Frame Build Process

• Nonsense! CNC machining complex shapes from billet is expensive
• This stamped/polished/riveted stainless box latch costs a few $US
• Start with thinnest possible sheet of #3 rough brushed AMS SUS303Cu that meets structural rigidity requirements
• E.g. steel utility knife blades are ~0.3mm, plenty strong
• Laser-cut, or stamp all cuts with one die for precision
• Roll-bend into box frame & laser-weld corner joints
• Smooth-polish all sharp edges
• Plenty of stamped sheet-metal parts factories can do this
• One piece: box frame, crossmember between battery & components, thin diagonal crossmembers between display & battery
• Add corner protection rods & lanyard loop with laser weld

“But Stainless Steel is so Expensive!”

Materials Selection: Body

• “Kevlar for the Masses”
• Injection mold into any shape (& color) you want
• Example: Nikon D5500 monocoque camera body
• Impressively stiff, strong, light, impact-resistant
• RF-transparent for antenna compatibility
• Cost dropping rapidly, capabilities improving e.g. http://tinyurl.com/h98xzfo

Canon camera dropped on concrete --->

• Big hole = magnesium/aluminium alloy
• Scuffed bits = LFRP

Long fiber reinforced thermoplastic (“LFRP”)

Materials: Body Build Process

• Massively helpful: http://tinyurl.com/hd43958
• “Antenna carrier” backplate
• Antenna cables are huge (1.3mm)!
• Mold channels for them into backplate
• Stainless power/wake button also lives here

• Antenna cable channels serve as grip ridges protruding from backplate
• They also protect power/wake button from accidental presses (e.g. while in wallet)
• Power/wake button falls naturally under index finger (in portrait orientation)
• Flush-mount Knowles Digital MaxRF noise-cancelling mic (4x3x1mm) & PUI Audio APS2513S piezo speaker (25.2x16.6x0.82mm) between backplate & “rear” PCB

Thin-wall injection-molded LFRP backplate

Materials: Component Build Process

• Double-sided SIM tray, 12.6x15.6x~2.0mm thick
• Inserts into in “camera” side of frame near LED
• Sandwiched between “front” & “back” PCB
• Holds two micro-SIMs or microSD + 1 SIM
• MicroSD reader on same PCB as SOC
• Only major dust/moisture ingress point besides microUSB port; seal it IP56 or better
• Made of 1200 aluminium; acts as LED heat sink

Stamped/cast 1200 aluminium SIM/microSD tray

Materials: PCB Stack

• 57x15x~4.0mm space to fit everything
• Typical smartphone 8 layer PCB = 0.4mm thick: 1 “front” & 1 “back” PCB
• Max. thickness of chips mounted on outer side of PCBs = 0.6mm
• Leaves ~2mm between PCBs for SOC/e-MMC PoP stack, SIM tray
• Cut flush-fit slot on PCB for JST SDWP604 IP57 USB port, protrudes 9.2x5.5x3.0mm
• Outer side of full-width “front” PCB: primarily mounts TDDI touch/display driver
• Smaller “rear” PCB: lower-bandwidth chips that don’t need many traces to talk to SOC

Tanyuan TGS-25 “ECarbon” thermal graphite sheet tape: ~0.04mm thick w/insulation

• Stick this stuff to every thermally active chip, & stainless frame
• Design to maximize graphite surface area, especially stainless frame contact
• Isolate LED w/separate thermal tape to USB cage, SIM reader, & stainless frame

Main printed circuit board stack

Materials: Component Build Process

• Two 5x3x70mm spaces along top & bottom, display side bezels are 3mm wide too
• Vertically-mounted 5x65mm PCBs double as battery holder, no chips on battery side
• Antenna cables routed through here, clipped in place
• Mount any small lower-bandwidth chips that won’t fit elsewhere
• Mount side-facing Knowles M-Stout receivers (4.8x10x~2.2mm) in side channels as close to camera plate as possible, laser-cut grille in stainless plates
• Mount Knowles Digital MaxRF microphones (4x3x1mm) on opposite end
• Mount ribbon cables to main PCB on 0.1mm carbon-fiber speaker box

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“Side channel” PCBs

Front View

Blue: power components (from left to right)

70x51x4mm 650Wh/L battery

JST IP67 USB connector

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Yellow: display, sensors, & lighting (from top to bottom)

CREE XQ-E R2 LED

Samsung 3.9” AMOLED display

Sony IMX208 camera (*)

VL6180X proximity sensor

*

“Side Channel” PCB/Rear View

Cyan: antenna cabling

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Red: audio components (from left to right)

Knowles Digital MaxRF primary microphones

Knowles M-Stout receivers

PUI APS2513S piezo speaker

Knowles Digital MaxRF noise-cancelling microphone

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Purple: PMD C08-001 linear resonant actuator

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White pizza box: dual-stack micro-SIM/MicroSD card tray

Under primary PCB (not shown): TDDI touch/display driver chip

Grey pizza box: Micron eMMC 16GB NAND/DRAM PoP, SDx25 SoC

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Primary PCB/Component View

Rear PCB/Bottom View

audio

power

radio

optical

haptic

Concept Evolution: “WalletPhone 2”

Key enabling technologies:

• Green PHOLED-based plastic OLED displays (1H 2017)
• Flexible Li-Po: Available now (http://tinyurl.com/ybqq2p8) but energy density ½ of best Li-Po; rapidly getting better
• On-cell/In-cell touch w/TDDI: simplify display design
• Challenge: flexible Gorilla Glass???

Basic concept design:

• Top/bottom rigid LFRP shells for PCBs sandwiched between display & LiPo, ribbon cable interconnects PCBs
• Use it like a flip-phone, but put it in your wallet & fold it up
• Can also be worn as arm band (e.g. velcro top & bottom)

Centrally-flexible smartphone w/dimensions of paper money

Other Crazy Device Concept: “BOD”

• Shaped somewhat like a DSLR camera; 4 NCR18650B 3400mAh batteries in handgrip
• Injection-molded LFRP monocoque body, HNBR coated, IP68+ weathersealed
• Bicycle mount, carabiner rail, ¼-20 tripod mount, camera neckstrap rails, etc.
• Primary functionality: 7” LTE tablet, Sony IMX264 5MP camera, 24-135mm f/2-f/4 lens
• Ambidextrous touch/haptic interface like WalletPhone; power/wake is only button
• Can charge a 5th 18650 battery, or use as reserve. Top side covered with solar panels

What else can “BOD” do? The sky’s the limit:

• Digital telescope. Rangefinder. Infrared camera (no low-pass filter on sensor). Good stereo speakers. Flashlight. Lantern. Compass. ANT+/802.11ah WiFi-HaLow/802.15.4 6LoWPAN radio. EPIRB/SPOT/etc. satellite messaging. Car starter. Fire starter (on USB cable). PMA/Qi/A4WP wireless charger. 18650 adapter charges other batteries.
• Anything else you can think of that can be integrated into a small/light device...

“BOD” stands for Bring OutDoors. This device is an adventurer’s dream.

“BOD” is a single device that integrates many many electronic outdoors devices.

https://community.zteusa.com/ideas/2018

Thank You! Questions/Comments?