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BLE112 (CC2540-based) and TPS62730

pazcal pazcal
Prodigy 90 points
Other Parts Discussed in Thread: TPS62733, CC2540, CC2541, TPS62730, TPS61200

Hello,

I'm working on a Bluetooth low energy application based on a BLE112 modem, and MSP4302416 processor. As described in BLE112 datasheet, we have had a TPS62733 regulator with a 2.3V output. Furthermore in our application, we used a ADC that needs at least 3.0V power supply. 

I cannot power the whole circut  through the TPS62733, because the ADC will not work properly at 2.3V. In the same manner, if I supply the BLE112 through the TPS62733, I will get voltage level mismatch between MSP430 (3.0V), and BLE112 (2.3V). Using level shifter is excluded.

So my questions are :

1) - What is the exact role of the TPS62733 for the BLE112? And can we really get a 20% energy saving when using 2.3V, instead of 3.3V?

2) - When supplying the BLE112 through TPS62733, what is the output level of Tx/Rx/CTS/RTS and other GPIOs?

3) - Same question, when bypassing TPS62733.

4) What is the MSP430 impact of power supply voltage drop (glitches  ?) on a running code?

5) All the application notes that suggest to use a TPS62733 work in standalone (no additional CPU). So when using an additional MSP430 with a 3V power supply (for the whole design), what are the real benefits of a TPS62733?

Thank's in advance

Regards

pazcal

  • 0
    TI__Genius 16010 points

    1. The TPS62733 reduces the peaks of current and improves efficiency by lowering the power consumption at the device, since it will be working at a lower voltage.

    2. Same as the supply voltage

    3. When bypassing, the CC2540 supply voltage is the same input voltage of the TPS62733.

    4. It greatly depends on how you are running the MSP430. You should check the oscillator frequency and supply voltage, consult the datasheet and determine the power consumption. It will have an impact, but of lower or greater significance depending on the application.

    5. The TPS62733 really shows its value at battery operated applications. If that is not the case with your application, the use of it would not be as critical.

  • 0 in reply to Lenio Cacula
    Prodigy 90 points

    Hi Lenio,

    Thank's for your answer...

    Regarding my question 4), I just wanted to know what will happen into MSP430 core (if supplied through TPS)  when the voltage drop from 3V, to 2.1V, or from 2.1V to 3.0V... What is the effect of voltage drop/glitch on the code execution? In other words what are the recommandations in term of power supply if I want to interconnect a BLE112, a MSP430, and an ADC with a Vcc >2.7V?

    And my last interrogation is regarding the usage of a TPS. I do not understand the benefits of a BYPASSABLE regulator. Why is it necessary to switch the BLE112 power supply to battery voltage (3.0V) when the BLE enters in sleep mode. Why could we not keep 2.1V when in sleep mode, and when not in sleep mode

    Thank's again

    regards

    pazcal

    Thank's in advance.

  • 0 in reply to pazcal pazcal
    TI__Genius 16010 points

    The variation of voltage will affect some of the parameters of the MSP430, but it should not interfere with its functionality, unless the DCO frequency is above the limit for a given voltage supply. Take a look at figure 1 of the F2416 datasheet. 

    When the CC2541 is in sleep mode, the efficiency gain of the TPS6273x is less than the gain of reducing the quiescent current. In bypass the TPS6273x will consume 30nA. In other words, if the TPS62730 does not go in bypass, the compromise will be power efficiency.

  • 0 in reply to Lenio Cacula
    Prodigy 90 points

    Yes but if I use a standard 2.1V LDO with a 1µA quiescient current, it will be the same in term of consumption, just 1µA instead of 30nA during sleep mode. So, I'm not sure that switching power supply is a reliable solution when running external processor, and ADC ^_^.

    Ok, So what is the solution to power supply correctly my design from a 3V battery : A MSP430, a TPS, a BLE112, and an ADC that needs at least 2.7V to run correctly?

    thank's again

    regards

    pazcal

  • 0 in reply to pazcal pazcal
    TI__Genius 16010 points

    Proportionally to the current, the LDO would certainly waste more energy than a switcher.

    Considering the 2.7V limitation, the TPS62730 is probably not a viable solution for the application.

    One option is not to use a regulator at all, at the cost of not utilizing the full extent of the battery charge. That however depends greatly on the kind of battery used.

    Another option is to consider a boost converter, so the supply voltage will be steady even when the battery falls below the 2.7V threshold. You will find a large number of options, but one I could suggest is the TPS61200.

  • 0 in reply to Lenio Cacula
    Prodigy 90 points

    Thank's again...

    regards

    pazcal