I am using LM2623MM boost converter in my circuit. As you can see from the datasheet when EN pin is pulled to ground, boost converter is disabled. I am thinking about supplying GPS and GSM module from this boost converter and I would like to cut off the power(for low power consumption) of them pulling EN to ground. My supply voltage of boost converter is 3.7V. As I researched when boost converter is disabled, output voltage becomes Vin-0.3V which makes 3.4V. Working voltage of GSM module is over 3.5V, GPS is over 3V. So does these components consume power, even if boost converter is disabled?
I am using LM2623MM boost converter in my circuit
That is a link to a chip, are you using that chip and have built your converter circuit round it or have you a PCB board with it fitted?
The data sheet says:-
The LM2623 features a shutdown mode that reduces the quiescent current to less than an ensured 2.5 μA over temperature. This extends the life of the battery in battery powered applications. During shutdown, all feedback and control circuitry is turned off. The regulator's output voltage drops to one diode drop below the input voltage. Entry into the shutdown mode is controlled by the active-low logic input pin EN (pin-2). When the logic input to this pin is pulled below 0.15 VDD, the device goes into shutdown mode. The logic input to this pin should be above 0.7 VDD for the device to work in normal stepup mode.
So yes it does not disable the output, just the action of the boost circuit. So yes you will still get power consumption from anything attached to the output.
My supply voltage of boost converter is 3.7V.
So why do you need a boost converter, surly you need a buck converter.
Grumpy_Mike:
That is a link to a chip, are you using that chip and have built your converter circuit round it or have you a PCB board with it fitted?
I am trying to design the schematic diagram. I do not have the PCB with it fitted.
Correct. When you shut down the boost converter, it continues to supply at the input voltage level minus the drop of the commutation diode.
This is obvious from the circuit.
caneradiyaman6:
I am trying to design the schematic diagram. I do not have the PCB with it fitted.
Building any sort of switching power supply is not an easy job. It requires a PCB and is very sensitive to the layout. Also choice of actual components is very critical, you can't just use any old capacitors and inductors. And like I said "So why do you need a boost converter, surly you need a buck converter".
caneradiyaman6:
I am thinking about supplying GPS and GSM module from this boost converter...
My supply voltage of boost converter is 3.7V...
Working voltage of GSM module is over 3.5V, GPS is over 3V...
Grumpy_Mike:
So why do you need a boost converter, surly you need a buck converter.
Maybe I'm just being dense here, but if the supply voltage is enough to drive the GSM and GPS directly then why bother with the added complexity of any kind of regulator?
GSM modules are explicitly designed to work direct from a LiPo cell. They need the high current capability
without voltage drops due to intervening regulators! If you want to reduce power consumption shutdown
the GSM module itself, or switch the supply with a hefty P-MOSFET with low Rds(on).
Grumpy_Mike:
Building any sort of switching power supply is not an easy job. It requires a PCB and is very sensitive to the layout. Also choice of actual components is very critical, you can't just use any old capacitors and inductors. And like I said "So why do you need a boost converter, surly you need a buck converter".
My battery is 3.7V and GSM module won't work under 3.5V. So battery can supply power until 3V. However GSM will not work after a while. The purpose of boost converter is make the battery life longer.
MarkT:
If you want to reduce power consumption shutdown
the GSM module itself, or switch the supply with a hefty P-MOSFET with low Rds(on).
It looks like I will move forward like you said
Is your battery a suitably rated LiPo then? Freshly charged LiPo voltage is 4.2V, trailing down to 3.5,
at which point you don't want to pull high current pulses from it any more for safety reasons.
Over-discharging LiPo batteries is never a good idea, they repay you with fire.
My battery is 3.7V and GSM module won't work under 3.5V. So battery can supply power until 3V. However GSM will not work after a while. The purpose of boost converter is make the battery life longer.
The problem with that is that your converter will use some power itself as no converter is 100% efficient. The result being that the battery will drain faster than it would without the converter, meaning you might get little or no improvement in battery life, you might even get a reduction.
You can see the battery from here. GSM module consumes 2A current during TX burst. I was concern about voltage drops may cause reseting the module for this case. That's why I thought using a boost converter might be a good idea.
PerryBebbington:
The problem with that is that your converter will use some power itself as no converter is 100% efficient. The result being that the battery will drain faster than it would without the converter, meaning you might get little or no improvement in battery life, you might even get a reduction.
So according to this reply I understand that I should not use a boost converter.
MarkT:
Freshly charged LiPo voltage is 4.2V.
I did not know this information thanks for telling me. Maximum working voltage of my microcontroller is 3.8V. So In this case I have to use a regulator to make the voltage. Let's say 3.3V
MarkT:
at which point you don't want to pull high current pulses from it any more for safety reasons.
Over-discharging LiPo batteries is never a good idea, they repay you with fire.
There is a funny(quite short) datasheet of the battery. However, It is written that there is a protection for complety discharging. However as I understand from all this discussions using a boost converter is not a good idea and I will supply GSM + GPS module directly from the battery but how can I prevent voltage drops? For supplying microcontroller I will use a fixed 3.3V regulator
caneradiyaman6:
Maximum working voltage of my microcontroller is 3.8V.
Really? What sort is that?
This would be a critical piece of information which was required in the very first post. 