# Can the LTC1871 DC-DC step up converter deliver 3A?

#### jordiggie

Joined May 5, 2022
5
Just a quick question, I am not certain that this converter can deliver my desired amount of current.
The question being, if I power this boost converter with a 5V, 3.5A input, can it output 6V, 3.0A when asked of the device connected?

#### Jon Chandler

Joined Jun 12, 2008
190
If the input is 5v × 3.5A = 17.5 watts

And the desir3d output is 6v × 3A = 18 watts,

the immediate answer is no. You can't get more power (watts) out than you put in. That doesn't even take into account efficiency, which reduces the available output power.

#### jordiggie

Joined May 5, 2022
5
If the input is 5v × 3.5A = 17.5 watts

And the desir3d output is 6v × 3A = 18 watts,

the immediate answer is no. You can't get more power (watts) out than you put in. That doesn't even take into account efficiency, which reduces the available output power.
I'm sorry, I should have specified my question more clearly. I was wondering whether the converter would be capable of delivering a 2-3 amp output current if the source has sufficient power (I.e. 5V, 4AMP. I am aware of the ~10% loss due to efficieny.

My worry is that the output current of the converter would be limited to something around 0.5 amps or below.

#### Alec_t

Joined Sep 17, 2013
12,807
My worry is that the output current of the converter would be limited to something around 0.5 amps or below.
The LTC1871 IC itself is just a controller for a DC_DC converter module. The module includes a switched transistor which has to handle the output power required. So whether or not your converter can provide the current you want depends on the manufacturer's choice of components (including heat-sink).
You need to consult the specifications of the particular module you have. Bear in mind that specifications of modules from dubious sources may be wildly 'optimistic'.

#### jordiggie

Joined May 5, 2022
5
The LTC1871 IC itself is just a controller for a DC_DC converter module. The module includes a switched transistor which has to handle the output power required. So whether or not your converter can provide the current you want depends on the manufacturer's choice of components (including heat-sink).
You need to consult the specifications of the particular module you have. Bear in mind that specifications of modules from dubious sources may be wildly 'optimistic'.
The current module I am looking at is the
LTC1871 DC-DC step up converter 3-35V 6A
LTC1871 3.5V～35V 100W DC-DC Step up Power Supply Boost Module
I'm not certain if this is exactly what you mean but I assume it is.

#### Ya’akov

Joined Jan 27, 2019
5,657
According to the datasheet the absolute maximum output current is 50mA, but the IC is an N-channel MOSFET gate driver and isn’t intended to provide the output directly to the load. THe datasheet provides design guidelines for MOSFET selection based on RDSon and maximum total gate charge. The limiting factor will be the power MOSFET, not this IC.

#### Ya’akov

Joined Jan 27, 2019
5,657
The current module I am looking at is the
LTC1871 DC-DC step up converter 3-35V 6A
LTC1871 3.5V～35V 100W DC-DC Step up Power Supply Boost Module
I'm not certain if this is exactly what you mean but I assume it is.
The LTC1871 is the IC being used to control the module, not the designation of the module itself. You‘ll need to link to the product you are considering to get more information.

#### ElectricSpidey

Joined Dec 2, 2017
2,146
It is typical of the Chinese to use the controller model number to identify the entire device.

#### Ya’akov

Joined Jan 27, 2019
5,657
It is typical of the Chinese to use the controller model number to identify the entire device.
Yes, but it isn't specific so it's not enough information.

#### Alec_t

Joined Sep 17, 2013
12,807
I'm not certain if this is exactly what you mean but I assume it is.
Yes, that's the spec, albeit somewhat minimal.
There's no indication if 100W is a continuous rating or peak rating. Most likely the latter.
Note that 6A and 35V would not be available simultaneously.

#### jordiggie

Joined May 5, 2022
5
Yes, that's the spec, albeit somewhat minimal.
There's no indication if 100W is a continuous rating or peak rating. Most likely the latter.
Note that 6A and 35V would not be available simultaneously.
Okay thank you, I only need it for supplying a servo with 6v and a range of 0.5A - 3A

#### Alec_t

Joined Sep 17, 2013
12,807
6V at 3A should be well within spec, even allowing for 'optimistic' ratings.