How to setup TPS62730 ON/BYP pin in CC2541 keyfob design?

Kevin Chen18

Intellectual 510 points

Other Parts Discussed in Thread: CC2541, TPS62730

Hello, there

I am trying to understand how ON/BYP is configured in CC2541 keyfob design (tidr191.pdf).

ON/BYP is shorted to P0.7 of CC2541. When P0.7 (output) is high, TPS62730 is configured as DC-DC converter.

My understand is that system is configured at power saving mode.

When P0.7 (output) is low, TPS62730 is by passing, Vout follows Vin.

If my understanding is correct, how the setup sequence for P0.7 pin?

Should it be: 1) when turn on the system, P0.7 is set to low. (BY-PASS)

2) after the system is ON, P0.7 is set to high (DC-DC)

3) when Vin is low, P0.7 is set to low again?

Am I right?

Your helps are appreciated.

Kevin

over 8 years ago

0 Fredrik K over 8 years ago

TI__Guru** 106705 points

Hi Kevin,

When the CC2541 is in active mode, the DCDC is enabled. When the CC2541 is in low power mode, the DCDC is in bypass.

Cheers,
Fredrik

0 Kevin Chen18 over 8 years ago in reply to Fredrik K

Intellectual 510 points

Hello, Fredrik

When DCDC is bypass, the 3V Vin of battery is applied on CC2541 directly.
How could it be low power mode?

thanks.
changzhong

0 Kevin Chen18 over 8 years ago in reply to Fredrik K

Intellectual 510 points

Hi, Fredrik

Does active mode mean: broadcasting and transmitting?

thanks.
changzhong

0 Kevin Chen18 over 8 years ago in reply to Fredrik K

Intellectual 510 points

Hi, Fredrik

Sorry I have to ask another question here to get a better understanding.
At different places, I was told that at initialization, P0.7 is high.
My point is that when I turn on the power, before CC2451 is power-up, the power should go through TPS62730 first.
Since CC2451 is not powered-up yet, how can I set P0.7 high?

Thanks.
Kevin

0 Fredrik K over 8 years ago in reply to Kevin Chen18

TI__Guru** 106705 points

Hi Kevin,

Active mode is whenever the MCU and/or radio is running.

Low power and low voltage is not necessarily the same. The CC2541 will consume less than 1 uA in low power mode regardless of supply voltage. The DCDC regulator will have poor efficiency at such light load, so if you use the DCDC the total current consumption will actually be much higher.

When the chip is active and the current consumption is in the mA range , you will get improvements by enabling the DCDC. This is because most of the internal parts of the chip runs off a 1.8 V LDO. As you know, the higher the voltage drop you have over an LDO, the more power you waste. So, by using a more efficient external regulator to regulate your supply voltage from 3 V to 2.1 V you improve the total efficiency of the system.

Cheers,
Fredrik

0 Torbjorn Sorby over 8 years ago

TI__Expert 6315 points

Hi Kevin,

The sample software will:

Enable the DC/DC in active mode
Disable the DC/DC in standby/sleep mode

Special condition: if Vin is lower than a certain threshold it is not enabled.

0 Kevin Chen18 over 8 years ago in reply to Fredrik K

Intellectual 510 points

Hi, Fredrik

Well explain. Thanks a lot.

Kevin

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How to setup TPS62730 ON/BYP pin in CC2541 keyfob design?