Trade magazines are full of reports about Broadcom BCM20730 Bluetooth chip that is expected to have power consumption so low that devices will work for years of a single battery set. Here is their press release.

I don't get it. Yes, power efficiency is important, but chip manufacturers have been designing energy efficient chips for decades so far and modern computers and smartphones are full of those chips. Now some company claims they have some extremely efficient chip. How is that possible?

How is any kind of drastic improvement possible in such design?

  • \$\begingroup\$ Does anyone still have user's manual of its dev board, BCM920730EVAL_040, because I cannot find it on net? \$\endgroup\$ – KernelPanic Nov 14 '18 at 9:20

To put it simply, it doesn't do the same thing as older Bluetooth chips.

The new chip uses BLE, or Bluetooth Low Energy. This is a mode which transmits packets at a high bandwidth in very short bursts, enabling the exchange of data with a very low duty cycle. When transmitting or receiving, power consumption is comparable with standard Bluetooth, but the time that this actually happens is so short that it doesn't really matter.

The laws of physics haven't been changed, instead, the protocol has been changed (or, more accurately, a new protocol has been added to the Bluetooth spec.) I'm not sure what trade magazines you're reading, but this isn't the only chip to implement this protocol. It's a standard protocol, and TI and Nordic Semi also have implementations. Instead, 'Bluetooth' in this context doesn't mean what it used to. This isn't a bad thing, but if the magazines confused you to think that Broadcom (and Broadcom only) has made a huge breakthrough in Bluetooth technology, I'd re-evaluate my magazine selection.

I've been interested in giving it a try, and have been looking at Panasonic's PAN1326 modules as a start. They integrate a chip antenna with a filter/LNA and a TI CC2564 under an EMI shield in a little module (about 1 cm\$^2\$ - you might want to wait for a breakout board if you're uncomfortable with soldering QFNs or can't do a PCB layout). The CC2564 requires a 32.768 kHz clock input and power (1.7-4.8V), and provides a UART and I2S interface. It's available for engineering samples and in small quantities from Mouser and Digikey. [Sorry, that reads like an ad - no affiliation. Just a summary of the specs, check the full datasheet here]


There is a new feature in Bluetooth 4.0 called Bluetooth Low Energy (BLE) which makes this possible.

  • \$\begingroup\$ I don't get one thing - why would devices not consume that little power before? Why would they need that "feature" instead of just consuming less? \$\endgroup\$ – sharptooth Dec 9 '11 at 13:17
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    \$\begingroup\$ @sharptooth - The protocol is different. Previously, Bluetooth used slightly higher power transmitters and receivers, transmissions used large packets, and transceivers usually stayed on for the entire conversation. BLE uses smaller, faster packets, and shuts off most of the time, so it's lower power. It's not compatible with the old protocol. \$\endgroup\$ – Kevin Vermeer Dec 9 '11 at 13:42
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    \$\begingroup\$ The specific device (Broadcom BCM20730) is Bluetooth 3.0 \$\endgroup\$ – Kellenjb Dec 9 '11 at 15:10
  • \$\begingroup\$ Although maybe I am wrong... the google link he gave shows 3.0 on all of the top results but the press release says it follows 4.0 specs as well. For Example, see this wired article \$\endgroup\$ – Kellenjb Dec 9 '11 at 15:13
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    \$\begingroup\$ @Kellenjb Yes, it is Bluetooth 3.0, but still implements BLE. While BLE is included in the BT 4.0 spec, it is unclear to me how it might exist in a BT 3.0 device (but it obviously does). \$\endgroup\$ – user3624 Dec 9 '11 at 15:21

BT3 incorporates high speed Bluetooth that uses Secure Wireless @ 2.4ghz after authenticating at the the BT Classic mode.

BT4-BLE is a completely new stack and is not backward compatible with any other Bluetooth Stack.

This chip the OP is mentioned is a BT3 chip using Classic and BT4-BLE modes- They cannot run at the same time, and are setup during the programming phase.

BCM is forking out millions in advertising.. Texas Instruments has this chip AGEEESsss ago!! Gues what.. ALL IPHONE4s + IPHONE5 is using this baby! (not this chip exactly obviosly- one slightly altered for iphone, why because they love chanign everything.. still. Ti landed a multimillin contract.. sweeeeet)

2.4GHz Bluetooth Low Energy System-on-Chip Solution

And because of this multimillion contract- you can get this AWESOME chip for less than £2. Make a pcb with on board symetrical antenna, a crystal and 2 or 3 SMD caps.. and you got an intelligent blueetooth PCB for under £5- home made!

Anyway- using a 3volt coin cell this chip can live for 5 years! Some intermittent transmissions- liek for example weather station.. 2-3 years.. Add a nice lithium-polymer battery.. boom- 10 years!

The standard for BT4 is amazing, its completely restandarised from 2.1 and 3. Supports Near Field Communication and PIN less communication. The way it sends, and senses packets is the biggest change- and thanks to that it can use almost no energy while waiting.

  • \$\begingroup\$ As with the comments above, this device that he is talking about is BT3.0. Your answer has no technical aspects to it at all and really doesn't even come close to answering the question. Oh, and there isn't even an Iphone 5 yet, so not much reason to talk about it :-) \$\endgroup\$ – Kellenjb Dec 9 '11 at 15:24
  • \$\begingroup\$ YEA BT3.. BUT BLE IS A STANDARD OF BT4! Get your facts straight. Read the article carefully. Notice how it supports BT4.. SO how the hell can BT3 support BT4? Forward Compatibility?? never heard of such nonsense! This by standards is a BT4 chip.. but maybe the keybaord products are aimed at BT3.. -1 trigger happy broadcom.com/products/Bluetooth/… \$\endgroup\$ – Piotr Kula Dec 9 '11 at 15:36
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    \$\begingroup\$ PS - Umm- the iphone5 is in production as we speak- based on the iPhone4S- just without some bugs and a faster dual core ARM.. and some new smarter looking outer case.. which nobody knows how it looks yet. \$\endgroup\$ – Piotr Kula Dec 9 '11 at 15:39
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    \$\begingroup\$ Just days before the iPhone4S was officially announced many of the rumors were still wrong. Surely there is a new iPhone in the works, but we base our sites off of facts, not predictions. As for BT3 vs BT4, It could be possible that BT4 devices can work with BT3, and I believe this is the case here. And still you don't have any technical information in your answer. \$\endgroup\$ – Kellenjb Dec 9 '11 at 16:04
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    \$\begingroup\$ I did allot of research on this. pure BT3 is not directly compatible with BT4 BLE. and pure BT4 BLE is not backwards compatible. Maybe some people have more info than rumours ;) We are talking about BLE the whole time though! not just normal stack. ANd that is what the hype is about \$\endgroup\$ – Piotr Kula Dec 9 '11 at 16:37

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