Power saver in buck boost regulator TPS61201

[vinodstanur]

Hi,
I am using lipo battery 3.7v and want to drive a circuit which works at 3.3v. My battery voltage can be in between 4.2v to 3v. So I selected TPS61201 buck boost regulator.
Is it a good choice ? My circuit current consumption in idle mode will be around 10 mA and some time it goes to 150 mA for few seconds and again comes down to 8 to 10mA.
I have a plan to reduce the idle mode current by using an accelerometer with interrupt which wake up the total system on shaking. At this time the current consumption will be negligible but I am worried about the buck boost regulator will take some power...
I can see a PS pin in the TPS61201 regulator and it says it can be used as power saver mode for the regulator and the efficiency chara shows that it have efficiency around 40% when the o/p current is as low as <1mA and close to 0mA.

So I have few questions,
Is it a good decision of selecting the TPS61201 buck boost regulator in this case? (3v to 4.2v -> 3.3v regulated)
What if I am taking zero o/p current or around 0.1mA O/P CURRENT? What will be the current consumed by the regulator at that time?
Also I am confused if I should always enable the PS (pull it down to enable power saver mode) even if the circuit takes its peak current around 150 mA. At this peak current will it cause any problem if I am enabling the power saver pin?

 

[tpetar]

At low load currents, the converter enters the Power Save mode to maintain a high efficiency over a wide load current range. The Power Save mode can be disabled, forcing the converter to operate at a fixed switching frequency.

Pin PS Enable/disable Power Save mode (High = disabled, Low = enabled). Do not leave floating.

**broken link removed**

Device Quiescent Current less than 55μA.


All ok, you can use it.


Best regards,
Peter

;-)

 

[vinodstanur]

At low load currents, the converter enters the Power Save mode to maintain a high efficiency over a wide load current range. The Power Save mode can be disabled, forcing the converter to operate at a fixed switching frequency.

Pin PS Enable/disable Power Save mode (High = disabled, Low = enabled). Do not leave floating.

**broken link removed**

Device Quiescent Current less than 55μA.


All ok, you can use it.


Best regards,
Peter

;-)

Thanks
So the Quiescent Current is less than 55μA only if it is in power saver mode right? (PS = GND) ? Will it be same if Vbat <3.3v?
So in my application I think I can ground the ps pin permanently I guess...

But is there any drawback if I am using the power saver mode?

 

[FvM]

It should be mentioned that TPS61201 isn't a buck/boost converter. It's a boost converter with an additional linear regulation feature. This means, for Vin > Vout, efficiency drops to that of a linear regulator.

Power save mode is mandatory, if you want to manage low loads with good efficiency. Main drawback is increased voltage ripple at low frequency.

 

[tpetar]

Thanks
So the Quiescent Current is less than 55μA only if it is in power saver mode right? (PS = GND) ? Will it be same if Vbat <3.3v?
So in my application I think I can ground the ps pin permanently I guess...

But is there any drawback if I am using the power saver mode?

Yes keep power save permanently.

The power save mode allows the converter to briefly turn off when low output currents are re quired and the present output voltage is at or above its set value. The manufacturer specified low output current efficiency increases from its regular value in the low tens, to around 50% simply by automatically turning off the converter when possible. The low efficiency means that the device is not well suited to provide output current of less than 10 mA unless the power efficiency mode is active. In this case the listed peak efficiency is achieved with a load from the high tens of milliamps to hundreds of milliamps.

See this document:
https://prod.sandia.gov/techlib/access-control.cgi/2007/075630.pdf


FvM mention drawback.




Best regards,
Peter

;-)

 

[vinodstanur]

It should be mentioned that TPS61201 isn't a buck/boost converter. It's a boost converter with an additional linear regulation feature. This means, for Vin > Vout, efficiency drops to that of a linear regulator.

Power save mode is mandatory, if you want to manage low loads with good efficiency. Main drawback is increased voltage ripple at low frequency.

Hi Sir,
The reason why I selected the TPS61201 is to use the battery even if it is discharged to around 3v. But I am stopping the battery usage at 3v. The battery discharge curve shows that aroud 3.3v , the discharge to 2.7v is sudden so I think I am not utilizing the boost regulator that much. Also the boost regulator is making some problems in magnetometer reading as it is fluctuating too much if I am using TPS61201 regulator, I am not sure if it is due the the flux leakage from inductor, didn't tried with an alternate sawtooth power supply anyway...

So what is your opinion about using some linear regulators like **broken link removed** instead of this boost regulator?

 

[FvM]

If low noise is a main objective, you should decide for a linear regulator.

 

[tpetar]

I found some alternative ICs, maybe its iteresting to see:

LTC3531 200mA Buck-Boost Synchronous DC/DC Converters
https://www.tme.eu/en/Document/285b0117a077d939d4e5677a7ac72fd5/3531fb.pdf

Operate from input voltages above, below or equal to the output voltage. The topology incorporated in the ICs provides a continuous transfer through all operating modes, making the product ideal for single cell Li-Ion and multicell alkaline or nickel
applications. The converters operate in Burst Mode, minimizing solution footprint and component count as well as providing high conversion effi ciency over a wide range of load currents.

Ultra Low Quiescent Current: 16μA
Up to 90% Efficiency



TPS63031
**broken link removed**

Device Quiescent Current less than 50μA
Up to 96% Efficiency


How you standing with soldering of 10-Pin QFN package ?


Best regards,
Peter

 

[vinodstanur]

I found some alternative ICs, maybe its iteresting to see:

LTC3531 200mA Buck-Boost Synchronous DC/DC Converters
https://www.tme.eu/en/Document/285b0117a077d939d4e5677a7ac72fd5/3531fb.pdf

Operate from input voltages above, below or equal to the output voltage. The topology incorporated in the ICs provides a continuous transfer through all operating modes, making the product ideal for single cell Li-Ion and multicell alkaline or nickel
applications. The converters operate in Burst Mode, minimizing solution footprint and component count as well as providing high conversion effi ciency over a wide range of load currents.

Ultra Low Quiescent Current: 16μA
Up to 90% Efficiency



TPS63031
**broken link removed**

Device Quiescent Current less than 50μA
Up to 96% Efficiency


How you standing with soldering of 10-Pin QFN package ?


Best regards,
Peter

Hi,
I am soldering the TPS using hot air pump.. ;-)

Here are my observations.
1>When I am disabling the TPS, 164uA current is consumed! Dono where it is going...
2> When I am applying directly 3.3v to the circuit without using TPS, it shows a current of 4.5mA.
3> When I am connecting TPS regulator in between and if I am increasing the the input voltage from 3 to 4 v, the current is as show below...

Observation:

input voltage (V) | input current (mA)
3v 6.25
3.3v 5.75
3.7V 5.5
3.9V 5.6
4V 8.5

It seems like taking too much current

 

[FvM]

We are yet missing the full application circuit used for the tests.

 

[vinodstanur]

We are yet missing the full application circuit used for the tests.

Thanks, now I checked my design and I found out one problem. I connected a 15k resistor from Vbat to one of the ADC pin of AVR. When AVR is powered OFF, (means TPS is disabled), most of the current around 200uA is flowing through that resistor via the AVR adc input pin...

After removing that connection, it is showing only 3uA when the device is disabled! Seems like good even it is taking 3uA when not in use...

 

[vinodstanur]

Hi,
Since there is a magnetometer in my circuit, the boost regulator is making more trouble in the stability of the readings from the magnetometer... So I am trying to use an LDO but the problem is the load regulation seems to be worst when the lipo battery voltage comes down around 3.6v from 4.0 v.
But I am supposed to use the battery till it reaches 3.0 V...

One more problem is, I am trying to save more power in my circuit, I am keeping a mosfet switch for a bluetooth module (HC_05) to turn it OFF completely but when the bluetooth module is switched ON, its taking too much current (transient). This some time makes issues as the instantaneous voltage comes down to 2v from 3.3v even if I am using the boost regulator.

What we will do in these type of situations? Also what regulator should I use in this case?