DC-DC voltage converter.
|Input voltage:||8 - 24V|
|Output voltage:||+5V lub +3,3V|
In many digital circuits it can work instead of 7805 line stabilizers. High efficiency allows to avoid heating up during work to high temperatures just like it happens when we use 7805 stabilizers. These circuits have worked successfully for years in ATB start-up kits and in other modules manufactured by Atnel company. Miniaturization of the circuit has allowed to keep almost the same dimension as the 7805 linear stabilizer. Latest generation converters ATB-PWR-3 are equipped with logic that allows to control their work (enabling/disabling) even from microcontroller level. Output voltage is selected using a jumper. Of it is open by default there is +5V voltage bon the output. When it will be closed input voltage will get +3,3V. Moreover the converters are equipped with a key built-in- SMD micro-switch type that allows for convenient manual power switching by a user at any moment. SMD jumpers on the converter a provide reconfiguration of its simple logical functions. A8498 chip is a heart of the module, with its nominal current efficiency 3A! So it has quite large reserves. The converter efficiency was limited due to miniaturization and use of a choke which max. current is 1,3A what limits the entire module efficiency. Despite this we can successfully use it in most applications for digital projects and also or even especially when we use ADC converters built-in a microcontroller. Proper and constant noises on converter output provide the ability to use oversampling when you want to get an extra bit of resolution for the built-in 10-bit converters.
The latest versions if the converters are blue. Dimension: high 14,7mm (without gold pins, only a choke and a capacitor in a metal housing were taken into account, like in the picture below), width: 16,5, length: 25,5 mm.
At the beginning we present a simplified version a of a manual for our converter. The newest version of ATB-PWR3 has easy logic built-in and thanks to it we can quite easily configure working mode of the converter.
By default it is mode no. 2 from the table presented below.
|(1) 7805 mode||(2) Switch mode (by default)||(3) Switch mode and PWR DOWN|
1. 7805 mode
To get such functionality of the converter as we get in a popular linear stabilizer 7805 (lack of any control logic) it is enough to short with a drop if tin the SMD jumper signed as JP2. At this point, the whole logic of the system is switched off. After power voltage connection on the converter input, it is switched on immediately and on an output we get one of two voltages selected by JP1 jumper. By default it is open (jumper taken off), so on the output we +5V voltage. If we are not going to use logic in the converter at all then we can solder out both JP2 gold pin pairs and JP3.
2. Power switch mode (factory settings/by default)
This mode provides a possibility for a system activation powered by the converter using a switch. For that purpose we can use two pins at JP2 jumper from the bottom of the converter. We can lead out the switch outside the device housing using a pair of cables. If it is not needed then we can use also (simultaneously) a micro-switch built-in placed on the converter. It is very convenient option during prototyping own devices on breadboards. After input voltage disconnection we always get a moment for final check visually if there is no short circuit somewhere. After that it is enough to click the micro-switch to launch the prototype.
3. Power switch and PWR DOWN pin mode
The mode described in the point no. 2 can be enriched with functionality that allows for system power control through e.g. a microcontroller that works in it. Thanks to it, a device after manual activation by an operator may perform demanded work even long-term without man attendance. After it is finished , the microcontroller (program) can switch off the power by itself what significantly reduces power consumption by the device. Where can it be used? Our company successfully uses such solutions in equipment of passenger cars or buses city transport when a controller equipped in such converters work basing on an accumulator power supply and a primary goal is to minimize current consumption.
Below we present comparison of power parameters quality (ripple) between standard 7805 linear stabilizer and our converter ATB-PWR3, at current consumption 500mA. Measurements were made using RIGOL DS4024 digital oscilloscope (200MHz).
|Ripple at about 10mV||Ripple at about 20mV|
As you can see in the comparison our converter can definitely replace the 7805 stabilizers in most of applications at the same it provides better parameters when it comes to efficiency and power loss that in case of the stabilizer are emitted in form of large amounts of heat. In the tested system, the 7805 stabilizer warmed up to a temperature of about 80 C degrees and our converter was only a bit wormer (about 29 C degrees). Anyone who used the 7805 stabilizer just once knows how much it warms up during normal work. At current consumption over 200 mA we must use huge radiators to eliminate this effect somehow. Although usually content of every housing including a PCB board where the stabilizer is placed - is heated up very strongly what very often leads to unexpected behavior of the entire system, especially when the ambient temperature e.g. in summer also strongly increases. Using our converters you get rid of problems like this once and for all. Below – brief comparing animation of 7805 stabilizer and one of first (oldest) versions of our converters.
FOOTPRINT for EAGLE:
To use the converter conveniently when we design own circuits in which we want to use it we prepared especially for this occasion so called footprint and in fact the entire library component for popular Eagle program. Below you can see the element looks in a PCB scheme and also you can download a zipped file with a library containing several library elements of the Atnel:
Module available on our online store: