ULN2803 Low-Side Drivers and UDN2983 High-Side Drivers - YouTube
https://www.youtube.com/watch?v=rmnAZlvBcl8

Transcript:
(00:05) hi this is Roger from can collapse and today it's about the popular uln 2803 a Darlington driver chip or as you see it's a whole family ranging from 2801 aid up to 2805 a we'll talk about the differences later as I've had written here they are so called low side or sync drivers so what many don't know there is a companion series of ICS which are so-called high side drivers the UDM not ul and UDN 2981 through 2984 we'll talk about them in the end there you can do nice things with them for example they
(00:59) go up to 80 volts they can switch up to 80 volts anyway let's go back to the basic data of the UL n 2800 it's serious the output current can be up to 500 milliamps but be aware this is not true if all outputs are switched on at the same time we will also talk about this later about what the datasheet tells us in detail the IC can switch considerably high voltage 50 volts is quite high we have integral suppression diodes that's what you see here each output has a so called freewheeling diet and they all
(01:47) are tied together to a common output or common pin and we have versions versions and that's the difference between the different numbers for all popular logic families on not only TTL and five-fold CMOS but also other logic families and what many don't know the outputs can be paralleled but let's start with the use of these what's the intention behind these eight freewheeling diets so when you apply a load to the output and the output is the collector of an NPN darling all the all the emitters of the eight Darlington
(02:36) transistors are tied also to a common pin to a common ground now let's suppose you're switching an inductive load which can be a relay coil or a magnet or something like that and you connect them to VCC so that's the Bart this is here the pin out of let's say output one two three four five or up to eight and your load is always connected to a positive voltage on the other side so that's where they call low side drivers when this transistor turns on it pulls the load to ground to the low side of your
(03:25) power now what happens when you switch on an inductive load like the relay call well when you switch it on there is nothing that can do any harm happening the current will rise linearly so there's no problem but what happens when you switch it off well then due to the breakdown of the magnetic field you will get an induction with reverse polarity so if if we beforehand had the positive side here and the negative side of the load here now induction will create a positive voltage here and a negative voltage here and this voltage can be
(04:19) hundreds sometimes even thousands of walls and that would destroy the output transistor if we don't have any means to get rid of this voltage now simple as it is just use a diet and now the induction generated voltage and current current will circulate here and the voltage here is safely on the on the collector of the output transistor is safely limited and this is what it's called a freewheeling diet because when you switch the power supply of an inductive load when you switch it off then the inductor is
(05:12) hanging in the air its freewheeling and to get away with the high generated induction voltage just use the freewheeling diet and as you can see it's exactly as they have already integrated this one here you they all have a common connection and this common connection you have to and this would be here you have to connect this this is pin number 10 of the IC you have to connect this to the positive voltage of your supply for your loads so that's a nice feature that you don't need any external diodes for switching inductive
(06:08) loads and now I hope you I hope this became clear how you use it and now let's go over to the other specific details of the UL and 2800 x-series so here we see the schematic of the five different types as you can see they all have the freewheeling diet they all have a discretely built a dot NPN Darlington transistor with integrated base emitter resistors and the difference the the range of the base emitter resistance and a depending on the family type a base resistor so let's take a look at the five different types the
(06:59) first one the 28 or one a is for P Mo's which is two in today's world not used anymore but also for CMAs the you LM 2803 is for 15 to 14 to 15 volt P Mo's also not used very often today and the most used one is the universal type for 5 volt TTL or and that is important for 5 volt CMOS you will also be able to switch the Darlington's on with 3.
(07:41) 3 volts although they are basically specified for 5 volts so if you have a micro controller output with 3.3 volts high they also will safely turn on the output if you're using the universal type 2803 a but also today still CMOS is still used the standard Sima not the h-scene CMOS is also still used because standard CMOS is capable going up to a voltage of 15 or some ices even can go up to 18 volts that can be quite nice in in some analog or digital circuitry to have 5 volt 15 volt switching capacity and for if you are using CMOS with higher than 6 volt
(08:41) VCC then you should or have to use the UL and 2804 a the o4 is important because it has a different base resistor otherwise the current from a high output from a 15 volts Emil's would there would be too much base current and that drops or that draws the CMOS down and the the current is then the base current would be higher than is usually allowed with standard CMOS and we have a last one the 2805 that is for high out TTL I'm not sure what they mean by high out TTL so perhaps somebody can can give an explanation in the comments but the two
(09:41) types that are mostly used is the universal 5 volt one which you can connect to basically all 3 point 3 to 5 volt digital outputs no matter if they are TTL or CMOS and the second most used one is the 2804 4 let's call it high voltage CMOS or PMO's if you still have any ICS that are working with P Mo's so let's take a closer look at the data sheet we have the output voltage of 50 volt the 500 milliamps max continuous collector current that we already knew but what you also should take into consideration the collector emitter
(10:29) saturation voltage can be as high as 1 point 3 volts even in worst case 1 point 6 volts so if you're working with only a power supply of let's say 5 volts and you're switching really 500 milliamps at one output then here on the collector emitter we can have up to 1.6 or was the highest yeah what in worst case you have to take into consideration there could be already out of this 5 volt that you are using here 1 point 6 walls can be at the collector emitter so they are remaining only three point four
(11:16) walls and your load should be safely working also when taking into consideration this missing one point six volts so next is the turn on and turn off delay time which might look with a quarter of a microsecond or 250 nanoseconds that might look relatively fast but in today's world of fast microcontrollers you can get a problem if you're switching for example in multiplexing big LED matrices this can be a problem even with an Arduino with it's 60 megahertz frequency you have to take this quarter of a microsecond into
(12:08) consideration so that you don't get into the situation that perhaps two outputs are conducting because you didn't realize that it takes some time for one output to switch off and also for the next one to switch on and now finally we take a look at the true output current that you can get we already know a 500 milliamps is the max output current you can get but the recommended maximum current is only 400 milliamps and now it depends on how many outputs you are using at the same time so if you think that you can turn all eight outputs on
(13:05) in parallel and get 500 milliamps out of them no you don't get with a what's called the duty cycle of a 100% that means all are turned on the whole time you only get 100 50 milliamps per output so the if you multiply this then you get a total output current summed up of 1.2 amps but only from all outputs if they are parallel or each one will give you only 150 milliamps now for the 500 the 400 milliamps limit for continuously turned out turned on outputs is only valid for a max of two outputs here we still just
(14:00) can get two outputs with a duty cycle of 100% which means always on two outputs can really supply 400 milliamps at the same time for an extended period but if you are multiplexing and you know or mustn't be multiplexing but anyway if I'm not if the outputs are not turned on the whole time then let's take the maximum if if you are really using all eight to all eight outputs turned on but only for let's say 28% of the time which means you have a PWM signal where the on time is 28% of the period or in other
(15:03) words the off time would be 72% then you can really get 400 milliamps out of all eight outputs if it's not for an extended period but only for roughly a quarter of a period so that you should know for not destroying your circuit or in other words to build a reliable power circuit so and as promised we finally take a look at the companion Sirius to the uln 2800 X the UDN 2981 through 2984 the different numbering is again for the different logic families and there is still a there are two differences the first one we already saw they are so
(15:59) called high side drivers which looks like this you have your driver and the driver is connected with the positive voltage now and the output of the driver now the load goes to ground and that's why it's called high side drivers because VCC is now switched to the load and the loads if you have some of them are have a common ground connection this is sometimes necessary for example when switching VFD displays vacuum fluorescent displays which I'll make a separate tutorial about it's quite handy
(16:52) to have high sight drivers and their internal structure is a bit more complicated because it's easier for for IC manufacturers to build power NPN transistors you will see we have one two three four NPN transistors and only one P and P so they must take make some effort to in in silicon to get this high side driver switching here you can see they have a common connection to the positive power supply and the output then is here the the positive power supply is switched from the high side to the load compare this again to the low
(17:43) side drivers there are only two transistors plus the freewheeling diode as you can see we apparently do not have a freewheeling diet because usually you don't ah sorry I was wrong of course we have them here but of course in in reverse direction here we have the freewheeling diet going away from the collector of the output and here we have the direction to the output from the common ground to the output of the driver so there's one nice thing about them there is a standard type which can be used with a supply voltage from five to
(18:43) fifty volts that's exactly what the UL m 2800 x low side drivers can do but there is also a part of the family that can go I will make it a little bit bigger so that you can better see it there is also a family type that can drive up to 80 volts that's quite high already but not lower than 35 volts so you even have the option here to drive for for as low power guys and low voltage guys comparatively or relatively high voltages and I perhaps in in my in my video about vacuum fluorescent display I'll show you an application of this IC
(19:40) which I was quite a lucky that I found this IC by chance and it saved me a lot of silicon or discrete transistors when switching a VFD display so that was it for today some infos about the you LM 2008 Oh X low side and the 29 8x hi so drivers thanks for watching until next time bye from crane collapse by from Raja you
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