STMicroelectronics’ VND5004B – Drive Ground-Connected Loads Without a Sweat

Be it a fan, a turbine or any other kind of inductive or resistive load – keeping an eye on safety becomes difficult if large amounts of current flow. STM’s VND5004B and VND5004BSP30 high-side drivers are a nice way to work around the problem.

Understanding the part is best accomplished by looking at figure one. It shows an example of the VND5004 being interfaced to a microcontroller of choice. The resistors next to the GPIO pins are required to prevent latch-ups of the GPIO interface, as inductive loads can wreak all kinds of havoc in your circuit during switch-off.

Interfacing the VND5004 to a microcontroller is easy…

Driving large currents – the datasheet maximum of the part is at 100A – requires both security precautions and careful PCB design. ST tries to make designer’s life easier with the pinout – figure two shows that the output pins are multiplied.

Furthermore, a pad at the bottom provides both Vcc and a first-class opportunity to attach a PCB heatsink directly to the ICs die. This, sadly, is a problem for hand assembly – if you don’t have a reflow oven in-house, pass assembly to another firm or buy one.

“Doubling” pins spreads current across the PCB…

While undervoltage shutoff, thermal and short-circuit protection are relatively simple to understand, the official datasheet of the part does not provide any information on the actual voltage levels found at the sense pins – when used with an ADC; they are intended to provide feedback on the current drawn by the load.

More answers on this topic can be found in application note AN1596, which describes both the semiconductor topology used and gives practical advice on component behavour. When driving serious inductive loads, definitely do take a look at it before finishing your circuit.

Vishay’s NTCS0805E3222JMT Case Resistor

NTCs and other thermosensors traditionally come in through-hole packages. Vishays NTCS0805E3222JMT is an excellent SMD part which can be placed right next to the heat source or ground plane whose temperature value you wish to monitor.

Just as in the case of most other Vishay resistors, the part number NTCS0805E3222JMT stands for but one component in an entire family of values. In our case, particularly, we are looking at 0805 case resistor with a value of 2k2 Ohms at nominal temperature. The whole family is shown in the table contained in the figure.

Vishay provides a wide range of values for this resistor…

The data sheet for the component is relatively limited in that it only explains the deviation of the B values found in the individual parts. However, excellent and wide-ranging further amount of information is available by visiting the curve computation website found at www.vishay.com/thermistors/ntc-curve-list/ and shown in figure two.

The only issue related to the product is that it is – like most other Vishay design tools – based on VBA, and thus requires the presence of a real version of Excel. Nevertheless, Vishay’s part most definitely deserves your attention when looking for NTCs – being able to eliminate annoying and slow throughhole processes is a surefire way to bring and assembly cost down.

Vishay assists engineers when using their SMD NTC thermistors…

Takachi’s TWN4-2-6W

A frequently repeated bit of advice by the OEMsecrets crew involves looking off the beaten path. When looking for a ready-made case for your electronic trinket du jour, taking a look at the offerings of Takachi is an interesting alternative to classics such as Hammond.

Based in – you guessed it – Japan, the company has, so far, largely been focused on the domestic market, making good use of the Galapagos effect described in this video. Watch Video Here. However, Takachi recently started to branch out to Europe – the TWN4-2-6W is one extremely interesting example of the breed.

When purchased from a distributor like Farnell, you get a tiny case which is 2×3.5×6 cm in size and has a white body color. The situation, however, becomes more interesting once you look into the datasheet of the product – our Japanese case supplier provides a wide variety of different case sizes outlined in the table.

The TWN4 family is available in various sizes…

One especially interesting aspect of the product involves the availability of boots. This somewhat Japanese-English term refers to a rubber piece which can be tucked to the front and the back, giving the case both antiskid and slight antivibration properties – incidentially, Western Digital used a similar process in their external hard drives with great success.

Bringing a boot makes your case more resilient…

Using a prefabricated case makes great sense especially when you are dealing with small production volumes-keep in mind that the set up for injection molding can easily eat up $10,000. Comparing this to Takachi’s price of about three dollars when you buy 25 makes the product attractive for small series production.

Keep in mind that very small prototypes can be modified using a drill press in a fashion similar to figure 3. Alternatively, Farnell also offers a customization service for the TWN4-2-6W.

This component houses an RFID antenna…

Vishay’s TNPW Family – TNPW120614K3BEEA SMD Resistor

SMD resistors are seen as a component which “just exists”. Designers are usually not willing to give the part more attention – unless one fails or becomes unaccurate due to overheating or environmental problems.

Vishay’s TNPW family, represented here by family member TNPW120614K3BEEA, is an excellent candidate for all situations where high amounts of reliability are needed in a SMD package. The resistors most outstanding feature is its incredible insensitivity to moisture and heating. The datasheet claims that the parts keep their value even at 85°C and when confronted with a humidity of 85%.

Vishay prides itself on offering a wide variety of value and heat dissipation options, most of which are outlined in the table.

The TNPW family is available in various case sizes…

Let the OEMsecrets team share an old hint here: designing resistor values very close to the maximum allowed amount of power dissipation is a real anti-pattern. Especially when working in automotive or motor control scenarios, spikes will crop up – in many cases, using a resistor with a sufficiently large power dissipation capability is enough to neutralize them.

Finally, developers planning to use the parts in their project are well advised to contact their distributor. Vishay is willing to send lots consisting of parts in a single date code, which – in theory – should reduce the spread of the individual parts even further.

However, it is not sure whether this is even needed. Vishay claims that every single part is optimized using a laser trimming process known from traditional precision resistors. Furthermore, parts are tested on the one by one basis, which means that that promised accuracy should be met without issues.

Trinamic’s TMC429 – Control Many Stepper Motors in One Go

While controlling stepper motors – in theory – is easy, the devil hides in the details. Trinamic’s TMC428 was a total classic, which now got a more modern successor model.

Trinamic has long seen its various ICs as a one-stop shop for all things stepper motor. In the case of the TMC429, this policy leads to the design shown in our figure – the part uses an SPI interface to talk with the host and creates stepper impulses in various communication formats.

…the TMC429 can output digital or analog step signals

In both cases, however, additional ICs are needed for motor interaction. Trimatic provides a choice of various architectures, almost all of which can be used directly with the TMC429. This makes the product ideally suited to systems like 3D printers – robust digital SPI communication reduces the impact caused by switching noise and similar electronic niceties.

Trimatic’s IC is not limited to generating microsteps. The part also contains three inputs for Reference Switches – if your motor comes equipped with these, the algorithms in the switch can use them to improve accuracy and performance.

Finally, don’t forget to Visit Here when dealing with the part – Trinamic provides a wide array of application notes and supporting information related to both the TMC429 chip and to stepper motors in general.

Monitor Magnetic Fields with Honeywell’s SS411A

Switches tend to wear out as time goes by – the Hall effect provides a nice alternative to detect “presence”. Honeywell’s sensor division provides an interesting set of devices in the SS400 and SS500 families.

The neatest feature of the whole sensor family is their ability to work with wide supply voltage ranges – voltage inputs from 3.8V to 30V are acceptable. The open collector output should be well-known from I2C drivers, and makes circuit integration really simple. Thermal sensors compensate the hall sensor’s behavior over a thermal range from -40 to 150 degrees centigrade.

…Honeywell provides a set of example schematics for sensor interfacing

In terms of magnetics, various types of switching behavior are provided. The SS411, which saw a large amount of search interest recently, is a bipolar part. This means that it is tuned to both North and South-facing magnetic fields – one of the benefits of this approach is that the part can sense closely-spaced magnetic fields of different polarities.

Physical placement is significant when using polarized Hall effect sensors…

In addition to that, unipolar and latching parts are also available. Unipolar parts such as the SS441 trigger only when receiving a positive (south) field, making them ideally suited to detecting lever positions and similar problems. A latch enables and disables itself only on the presence of specific fields – if a south field enables it and disappears, the device will stay switched on. Latch, unipolar and bipolar parts can be ordered with various switching sensitivities, which – for example – enables you to use high sensitivity sensing when air gaps are large.

Honeywell shows itself extraordinarily flexible when packaging is concerned. In addition to through-hole sensors with various physical pin arrangements, the SS500 family packages the same sensor technology in an SMD case. For example, the SS511AT is but an SMD version of the SS411…

NXP’s PCF85063TP1Z – Providing Electronic Equipment with an Accurate Sense of Time

Providing electronic equipment with an accurate sense of time has always been an interesting challenge – more than one company dedicates its existence to this job. NXP, being the successor of Philip Semiconductor, continues the Dutch real-time counter expertise.

With the PCF85063TP, they offer a low-power part dedicated to timekeeping in both space and power constrained environments such as Wearables and similar products. From a technical point of view, the PCF85063TP is not particularly difficult. Figure 1 shows its internal block diagram consisting of the clock system and the I2C interface which the part uses to get in touch with you microcontroller or process computer.

…the PCF85063TP is a classic timekeeping IC

One interesting aspect of the design is the lack of a backup power circuit. The part is not intended to work as a full-blown calendar chip similar to the ones produced by Dallas and used in PCs – instead, the part works only while power is provided from the host system. When actually working, the behavior of the part – by and large – matches that seen in other NXP real-time clocks. Figure 2 shows the register layout, which should be well known to all those of you experienced with other real-time clock chips.

Never change a running system…

As mentioned in the introduction, the PCF85063TP stands out from other parts due to its low power consumption and low physical size. NXP managed to fit the entire electronics in an HWSON8 housing, which leads to physical dimensions of just 2 x 3 x 0.75 mm.

Nevertheless, and exp managed to fit in two very neat features. First of all, the part can output a clock signal to feed other parts. Secondarily, the actual power consumption is very very low – when fed with 3.3 V at the ambient temperature of 25°C, NXP claims that the normal standby current is in the range of but 0.22uA.

STMicroelectronics’ P0102BL – Ultra-Low Current Thyristors Make Switching Easy

Thyristors are usually associated with high-power designs. In some cases, however, a thyristor also is well suited to an application where low power consumption is needed – ST’s P0102BL is the tool of choice.

Its most outstanding attribute is the extremely low gate current. Firing off the P0102BL can be accomplished with but 200 Microamperes – other Thyristor types demand ten or even hundred times more current. The maximum amount of current handled by the part is 250mA – while not earth-shattering, the STMicroelectronics P0102BL can always be used to fire off a second thyristor.

While most low-power parts tend to have extremely low breakdown voltages, ST’s semiconductor manufacturing experience allows them to promise a Vdrm of 200V – not enough for UK or EU line power, but acceptable for US applications.

All those of you seeking a quick refresher on all things thyristor are well-advised to take a look at STM’s application note AN2703. Click Here to View the Application Note. It provides concise explanation of all important thyristor parameters, and is not limited to the P0102BL.

…STM provide detailed information on thyristor parameters

Sadly, those of you looking for a through-hole thyristor are out of luck – the part is only available in the SOT23-3L casing, which – however – should be hand-solderable with a bit of skill.

Texas Instruments’ LM4041 – When a Zener Just Doesn’t Cut it

Finding a good voltage reference is as difficult as asking a cigar afficionado for the perfect smoke – the answer depends on the mood and the character of the individual queried. TI’s LM4041 series provides a “common sense” solution for all those not desperate for the highest accuracy.

From a technical point of view, the LM4041 is but a better zener diode available in various three- and five-terminal SMD housings. This means that the responsibility for current limitation falls solely in the hands of the user – directly connecting the part to a high, unregulated DC voltage rail leads to catastrophic failure. Instead, the simplest possible approach involves a shunt regulator as shown in figure one.

…The protection resistor limits the current flowing through the reference

TI provides an adjustable version of the LM4041, which works via a set of external feedback resistors. In that case, total accuracy depends on both the resistors and the LM4041 – a situation which can become interesting as thermal drift takes place.

In general, TI promises an original accuracy of their 0.1 or 0.2% as shipped, with detailed data given on the influence of temperature changes on system performance. Sadly, TI does not specify much in terms of long-time stability: the maximum information given in the datasheet claims a 125ppm change in voltage output over 1000 hours. Nevertheless, the part – for sure – is interesting and should be at the back of your mind when working on data acquisition systems.

On Semiconductor’s LM324DR2G

When the LM324 opamp showed up in our OEMsecrets search trends, more than one engineer in our team was shocked – the 324 is one of the most beloved general-purpose operational amplifiers on the market.

A more detailed analysis of the issue, however, shows that not all versions of the LM 324 are affected. Instead, the discontinuation has hit only the part produced by ON Semiconductor. Visiting the website found at https://www.onsemi.com/PowerSolutions/product.do?id=LM324DG provides an even more detailed view shown in the figure.

Not all versions of the LM324 are discontinued…

Instead, it looks like ON Semiconductor wants to get rid of the traditional Tube type packaging used for providing small amounts of operational amplifiers. This approach is sensible – nowadays, evem small companies such as the one owned by yours truly can afford pick and place machines which, normally, don’t like being fed with components in tubes.

The part number LM324DR2G provides exactly the same part in a pick and place suitable form factor and is not affected – should you find yourself facing supply problems, it should be just a question of time until when distributors will break up the LM324DR2G tapes into smaller packages useful for-small-production runs.

Should you be unhappy with ON Semiconductor, you can also switch over to Texas Instruments. Their version of the LM324 has a slightly higher bandwidth, but can supply only 30 instead of the 40mA of output power.

Nevertheless, customers who absolutely need the LM324 in a tube are well advised to head over to OEMsecrets now. As of this writing, distributors still have quite a few tubes of this popular op amp. If you don’t purchase now, you might end up having problems later…