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Wireless Power Frequently Asked Questions (FAQ)

Wireless Power System

IDTP9020 Receiver and IDTP9030 Transmitter

 

 

Wireless Power System


Coil information


Can IDT also support the B1 coil?

The IDTP9030 supports all WPC coils (single and multi-coil configurations) that can be driven with a half-bridge inverter, DC-input of 10-20V, and a 110-205kHz switching frequency.  Within these parameters, both WPC as well as proprietary coils may be used.  On the receiver side, we work with all types of coils: WPC recommended (RX-A,B,C,D,E), custom coil modules, PCB based, flexible PCB etc.  Our solution provides a great deal of flexibility to support proprietary solutions, or coils made from different materials, such as PCB based coils in addition to wire wound coils.


Receiver coils can be designed onto FPCs - do you have a design guide to design it onto FPCs. My understanding is that the coil material must be copper to improve efficiency, or can it use aluminum coils as well?

Coil design is really an art, requiring extensive simulation using complex software.  So there is no design guide that is provided at this time.  If WPC compliance is desired, then utilizing one of the WPC-approved coils would provide the easiest path to Qi certification.  Aluminum is possible, but the losses would be greater and the efficiency lower.  However, these can be offset to some degree by greater area or coil volume – but then you venture away from a WPC-approved coil design.  So there are tradeoffs.


Some companies use 0.6mm thick coils. How thin can IDT support for receiver coils?

Any thickness can be supported – it’s an efficiency tradeoff and thinner coils will tend to result in lower efficiency, but this is the same for all solutions (it’s a physics issue).  Whatever coil module suppliers’ state-of-the-art solution is, IDT can work with these solutions.


Can the TX and RX coils differ in size? 

Different size coils can be considered but there will be a coupling and efficiency tradeoffs – please refer to the WPC discussion at:

 http://www.wirelesspowerconsortium.com/technology/basic-principle-of-inductive-power-transmission.html


What effects occur when considering different coil sizes?

Please refer to the WPC discussions at:
http://www.wirelesspowerconsortium.com/technology/basic-principle-of-inductive-power-transmission.html
http://www.wirelesspowerconsortium.com/technology/transfer-efficiency.html

Is it technically possible to support TX coils other than A1 or A6, such as A3, A4, A5, B1, etc. if we use multiple P9030’s?

We can support any coil configuration that requires 10-20V DC input.  For multi-coil designs, some additional passive components (switching FETS) would be required, but only one IDTP9030 transmitter IC is required as long as only a single device needs to be charged at a time.

Can the IDTP9030 detect which coil a mobile device is put on in a multi-coil configuration?

We sequentially ping each coil and when we find a coil that has sufficient coupling, we transfer power using that coil.
 
Will the other coils (in a multi-coil configurtion) be disabled (stop pinging) once the IDTP9030 detects a valid receiver on a coil?

Once we enter power transfer with a given coil, the other two will stop pinging.
 


NFC function (NFC = Near Field Communication)

 

Can Customers use the same wireless power coil and put firmware to IDT receiver for NFC? 

At this time, it is not possible to use same coil and customer firmware to do NFC. The antenna design of NFC, frequency, and communication protocol is significantly different from the WPC Qi standard.  In the future, it may be possible to use a combined coil, or a coil module that contains both coils together.
 

Interference


How can I resolve audio interference effects? 

Interference issue can be handled with proper shielding technique such as a ferrite plate under the RX coil to keep magnetic flux within a localized area. Further shielding can be achieved by adding a thin conductive plate behind this ferrite plate. These are largely system-level issues that depend upon total system design.  If interference is the concern, shielding at the system level is one approach that can be taken – the most cost effective yet sufficient method will depend upon the particular system.  In the most extreme cases, a conductive plate can be used which would suppress any interference.  But this isn’t necessarily required – it depends upon the particular system in question. 

 

Foreign Object Detection


In our previous evaluation, we needed to place “tin foil” to isolate the battery and receiver coil, because the battery could interfere with the charging. Can the IDT solution detection misplaced metallic objects such as tin foil?

We detect four different levels of “Foreign Object Detection” when using IDT’s Tx and Rx IC’s.  The thresholds & limits of each FOD level and the desired consequences (still go into power transfer, or stop power transfer) can be configured by the customer.

 

Reference Schematic and BOM cost


Can you provide reference schematics and an optimized BOM?

Yes, IDT will supply this upon request.


How much is the associated BOM cost of required peripheral parts for the IDTP9030 transmitter solution? 

The IDTP9030 requires approximately 30 passive components.  Excluding the cost of the coil module and the transmitter IC itself, the cost of these passive components is roughly $1.00 in high volume production.

 

System Standby Power Consumption


What is our no load standby power consumption? Does IDT meet Energy Star requirement?

The IDTP9030 Tx IC consumes roughly 9mA when there is no receiver on the transmitter.  This will be reduced in future versions of firmware.  Our current power consumption with 20V DC in is <0.2W, which we understand to meet Energy Star requirements. 
 


Wireless Power Consortium (WPC)


Does a customer need to become a WPC member to get access to WPC Spec and Qi Logo?

The WPC spec is public and can be accessed at the below link.  The Qi logo is only available for members who have submitted their products for WPC Qi-compliance – alternatively, a customer’s ODM may also take this responsibility to become a WPC member and submit the production for compliance testing.

 www.wirelesspowerconsortium.com/blog/11/qi-specification-available-for-download


Where can I find a copy of the Wireless Power Consortium (WPC) Standard?

 www.wirelesspowerconsortium.com/blog/11/qi-specification-available-for-download

 

Customer Programming


I understand the IDT solution has embedded microcontrollers (MCUs).  Can the customer program the MCUs directly to enable features and functions?

The IDT solution will offer some configurability for features like FOD (Foreign Object Detection) limits and behavior, but we don’t expect customers to have to program or access the MCU themselves for a standard engagement model.  We believe most customers will prefer to have a light or no-touch model where the firmware is preconfigured to enable the desired features without requiring MCU programming.

 

Receiver IDTP9020 and Transmitter IDTP9030


Qi Certfication:  Is the IDTP9030 certified?
 

Qi certification is provided for transmitter and receiver systems, not on a component or IC level.  IDT’s Tx-A1 (single coil, magnetically guided) evaluation board, featuring the IDTP9030 transmitter IC, has been fully certified by WPC to be Qi-compliant.  We’ll be submitting additional evaluation boards with other transmitter coil configurations as well as our receiver solution over the coming weeks.

 

Receiver Application

Will wireless power receivers be embedded in mobile phone?  


We believe this will eventually happen, but the more common implementations today are for wireless power receivers to be built into a battery door (backside cover of the phone), an aftermarket sleeve, or even into the battery itself. 


Rx Connection to Host


For ease of design, we would like to minimize the number of wireless power Rx IC signals connecting to our host.  How many connections does the IDT Rx IC require?

We look to the host simply like a 5V supply that they would use directly or input into a CMIC (Charge Management IC).  So we only have 1 pin connection to the host required, but if there’s a desire to have the Rx communicate system information back to the host, I2C lines or a GPIO status line would be required to update the Rx on the charging status of the system.

 

Package Size


I’m concerned that there’s not enough space to place the 7x7mm TQFN package of the IDPT9020 Rx IC into my application . Is there a plan for another package option?
 
The important constraint to understand is the total board area required for a solution.  Using the 7x7mm QFN, the board space required is approximately 250mm2.  The first version of IDT’s receiver IC has many features and a great deal of configurability, including support for multiple protocols (multi-mode or multilingual support) and two way communication and secure authentication.  The IDTP9020 will be offered in a smaller WLCSP (Wafer Level Chip Scale Package) later in Q2 and be ~4.6 x 4.9mm in size.  

 

Quiescent Current


What is the IDTP9020 quiescent current and will it draw power from my battery when it’s not in use?

The P9020 does not consume power unless power transfer from the Tx is occurring, and it draws all its operating power from the transmitter.  To restate this another way, no power is required from the system or mobile device battery, and the Rx IC doesn’t present a load or cause any incremental battery drain.

 

USB adapter


Does the IDTP9020 disable the wireless charging function automatically in the presence of USB power, or is there a need for the CPU to manage it via I2C bus?

The wireless charging function will be disabled automatically if there is a USB adapter connected, so no control lines to the host/CPU are required.

 

RX BOM cost


Is there a minimized BOM and schematic for the IDTP9020 Rx solution?      

Yes, this is available upon request from IDT.

 

Charging and Thermal Issues


Our current battery is 1800mA/h  and we’re consider 1C or 1/2C charge but are concerned about thermal issues. Technically, we can do 1/4C to address the thermal issue, but the resulting charge time will be too long.

The IDTP9020 can deliver 1.0A @ 5V in WPC mode or 1.5A @ 5V in proprietary mode, which gives you comparable charging times compared to wall chargers. The IDTP9020 Rx solution uses very high efficiency full bridge rectification and a buck converter, so thermal performance of our solution will be very good compared to competing solutions that use LDOs for the final DC/DC conversion.

 

Miscellaneous IDTP9030 Questions


We would like to have higher switching frequencies in the MHz range.  Can the IDTP9030 switch in the MHz frequency range?

We limit our upper frequency range to 205kHz, and while there might be some headroom above that, the IDTP9030 is not designed to switch in the MHz range.

 

Miscellaneous IDTP9020 Questions


If a battery of a mobile device is completely empty (such as 0V and 0mA) and this mobile device is then put on a Tx mat, how can the Rx send back packets at Ping phase? Is the device never charged since the battery starts out completely empty?

The mobile device battery does not supply power to the IDTP9020 receiver (Rx) IC.  The Rx IC is solely powered from the energy in the ping itself.  So charge a mobile device from a completely dead battery state is no issue.


 

IDT Proprietary (“Beyond-Qi”) Features


Is the back channel communication option capable of doing high speed transfer for mobile device firmware updates or picture transfer? 

No, the communication that occurs from Rx to Tx (part of the WPC communication standard) or Tx to Rx (IDT’s back-channel communication) is not meant as a high bandwidth communication channel.  It uses the energy transfer band to facilitate this communication and may be used for two-way authentication or passing of lower bandwidth information, but it’s not meant as a substitute for NFC, wi-fi, or Bluetooth.
 
What is typical/maximum transfer rate of back channel communication?


It’s in the 500bps to 1kpbs range.


Is two-way authentication possible without compromising WPC communication?

Two-way authentication requires communication between Rx and Tx, while WPC only supports Rx- to-Tx communication.  So by definition, two-way authentication is beyond the scope of WPC’s standard protocol, but including this “beyond-Qi” feature will not compromise the normal Rx-to-Tx communication required by WPC to module power delivery.


Return to the IDT Wireless Power product page: www.idt.com/go/WirelessPower