Electronic Circuits

Thursday, July 15, 2021

3.7V Li-Ion Battery Charger Circuit using MCP73831 IC + PCB

Electronic Circuits Battery Charger , Circuits to Assemble

Fig.1 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831

For Original Portuguese Version, Click Here!

The MCP73831 device is an advanced linear charge management controllers for use in space limited, cost-sensitive applications.

The MCP73831 is available in an 8-Lead, 2 mm x 3 mm DFN package or a 5-Lead, SOT23 package.

Along with their small physical size, the low number of external components required make the MCP73831 ideally suited for portable applications.

For applications charging from a USB port, the MCP73831 adhere to all the specifications governing the USB power bus.

The MCP73831 employ a constant-current and constant-voltage charge algorithm with selectable preconditioning and charge termination.

The constant voltage regulation is fixed with four available options: 4.20V, 4.35V, 4.40V or 4.50V, to accommodate new, emerging battery charging requirements. The constant current value is set with one external resistor.

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The MCP73831 device limit the charge current based on die temperature during high power or high ambient conditions.

This thermal regulation optimizes the charge cycle time while maintaining device reliability. Several options are available for the preconditioning threshold, preconditioning current value, charge termination value and automatic recharge threshold.

The preconditioning value and charge termination value are set as a ratio, or percentage, of the programmed constant current value.

The MCP73831 device is fully a specified over the ambient temperature range of -40°C to +85°C.

The Circuit

The circuit is very simple and uses few external components which facilitates the assembly and reduces the assembly cost, the standard charging voltage regulation is normally set at 4.2V.

However, there are variations in the nomenclature of the last digit of the IC that differentiate them from the standard charging voltage, such as:

MCP73831-2 = 4.2V
MCP73831-3 = 4.3V
MCP73831-4 = 4.4V
MCP73831-5 = 4.5V

The constant current charging value, is adjusted through resistor 2.2K ohms R3, which in our circuit is programmed for a ~450mA charge. Using a simple formula, we can vary this constant charging current:

Rc = charging resistor

CC = charging current in mA

Formula:

Cc = 1000/Rc

Being our 2.2K resistor, we have:

Cc = 1000/2.2

Cc = ~ 450mA

Remembering that the minimum charging current for this device is 15mA and the maximum current is 500mA.

Lithium-ion Batteries have become popular in large scale in portable electronic devices, due to them having higher energy density compared to other batteries on the market.

Benefits include thousands of recharges and none of the old, well-known “memory effect” problems we had in the first rechargeable NiCd battery cells.

However, lithium-ion batteries must be charged following a carefully controlled constant current (CC) and constant voltage (CV) pattern that is unique to this type of cell.

Overloading and careless handling of a Li-Ion cell can cause permanent damage or instability and a potential danger of explosion.

In Figure 2 below, we have the 3.7V Li-Ion Battery Charger Circuit schematic diagram, with the MCP73831 IC and we can follow and analyze the entire circuit, which is a simple and easy-to-assemble circuit, with few external components.

Fig. 2 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831

Features

Linear load management controller:
Integrated pass-through transistor
Integrated current direction
Reverse Discharge Protection
High precision preset voltage regulation: +0.75%
Four voltage regulation options: 4.20V, 4.35V, 4.40V, 4.50V
Programmable load current: 15 mA to 500 mA
Selectable preconditioning: 10%, 20%, 40% or Disable
Selectable end of charge control: 5%, 7.5%, 10% or 20%
Three-state status output - MCP73831
automatic shutdown
Thermal regulation
Temperature range: -40°C to +85°C
Packaging: 5 derivations, SOT-23
applications
Lithium Ion / Lithium Polymer Battery Chargers
Personal Data Assistants
Mobile phones
Digital cameras
MP3 Players
Bluetooth Headphones
USB chargers

Components List

U1 ...................... Integrated Circuit MCP73831
LED1 ................. Light Emitting Diode - Red
LED2 ................. Light Emitting Diode - Green
R1, R2 ............... 240 Ohm Resistors
R3 ...................... 2.2K Ohms Charging Program
Others ................ Wires, connectors, PCI, tin etc.

The PCB - Printed Circuit Board

We are offering the PCB, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home.

If you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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My Best Regards!!!

How to Read Ceramic and Polyester Capacitors Correctly

Electronic Circuits Electronic Components , Learning

Fig. 1 - Various capacitors - how to read correctly

The original Portuguese post, click here!

Due to many manufacturers and various norms and standards established nowadays, many acronyms are implemented in electronic components and use a wide variety of codes to describe their characteristics, which makes them difficult to read, there is an intrinsic coding to indicate the capacitors values, and manufacturers use different methods.

Sometimes generating a bit of confusion, some indications such as; tolerance and also the working supply voltage often aren't clearly written on them.

Will explain how to read the capacitors, identifying: microfarads (μF), nanofarards (nF), picofarads (pF), tolerance, voltage, and so on.

For values equal greater than 1000nF (eg with aluminum or tantalum electrolytics), they mostly write the value on the body followed by the abbreviation for microfarad (μF).

For values less than 1μF (1 microfarad), the issue is not so clear.

Generally, an encoding consisting of a three-digit number followed by a letter is used.

Before the most skeptics and purists come to question this Post, let us clarify that the correct abbreviation for microfarad is the Greek symbol; micro (μ). Which is a prefix of the International System of Units denoting a factor of 10−6 (one millionth).

Confirmed in 1960, the prefix comes from the Greek; μικρός (transliterated: mikros), meaning small. Followed by the capital letter F.

Usually when we're doing component descriptions, we don't always have the Greek symbols available on our keyboard, so to prevent this symbol from being wrongly transcribed, we substitute it for the lowercase letter "u", although we mustn't forget that we're always talking about the letter. "μ" (micro).

We have other cases, examples of this type, it is the symbol Ω (ohm) that is sometimes replaced by the letter "R" or, in some other cases nothing is written.

As mentioned at the beginning, with the exception of electrolytic capacitors that generally far exceed the value of 1 microfarad, the universe of capacitors used in electronics consists of capacitors with values ranging from a few pF or picofarad (ceramic or disk capacitors look like lentils) to those close to 1 microfarad or 1μF (multi-layer polyester).

Before continuing, it is worth remembering "for whoever forgot" the subject of submultiples.

Submultiples

A pF (picofarad) is the smallest submultiple that exists to "practically" indicate capacity. I say practical because there are still smaller submultiples, SI Prefixes (International System of Units)

(deci, centi, milli, micro, nano, pico, femto, atto, zepto and yocto), but they are not used in electronics. 1 picofarad is 1,000,000 (1 million) times less than 1 microfarad (μF).

Halfway between picofarad and microfarad there is another sub-multiple called nanofarad widely used and it is 1000 times larger than 1 picofarad and 1000 times smaller than 1 microfarad.

Typical Capacitor Values

For capacitors facing between 1pF to 1μF (almost all capacitors except for electrolytic), reference values are indicated with a three-digit number followed by a letter.

The first two digits indicate the starting number, while the third digit represents the number of zeros that must be added to the starting number to get the ending value.

The result obtained is necessary to consider it in picofarad.

Examples of encodings

Let's use it as an example; 4 types of captions written on the capacitors, as shown in Figure 3 below.

In the capacitor in Figure 2, we can see in the description only a set of three numbers "104", which representing the capacitance in Picofarad reading.

Figure 2 - Capacitor with only capacitance captions

104 - Which is its capacitance in pF, and without any further information.

The capacitor in Figure 3, we can see in the description the set of 3 numbers "400" which representing the working voltage, followed by the letter "V", which is the working voltage indication, and the set of three numbers below "104", which represents the reading in Picofarad.

Figure 3 - Capacitor with voltage and
capacitance value captions

400V - Which is the working voltage.

104 - What is its value in pF

The capacitor in Figure 4, we can see in the description the set of 3 numbers "104", which represents the reading in Picofarad, followed by the letter "J", representing Tolerance, and the set of three numbers "250" represent the working voltage followed by the letter "V", which is the working voltage indication.

Figure 4 - Capacitor with capacitance, tolerance,
voltage captions

104 - What is your capacitance in pF

J - It's the tolerance

250V - Is the working voltage.

The capacitor in Figure 5, we can see that in the description it starts with a number and a letter "2A" which represents the value of the maximum working voltage, then the set of 3 numbers "104", which represents the reading in Picofarad, followed by the letter "J" representing Tolerance.

Figure 5 - Capacitor with maximum voltage,
capacitance, tolerance

2A - Which is the value of your maximum voltage

104 - What is your capacitance in pF

J - It's your tolerance

Let's Practice:

Let's say you have a capacitor with the nomenclature written "472", just as we take resistor readings, the third capacitor digit is also the multiplier, which means it would be: 47 + 2 zeros, which means 4700 pF (picofarad).

So if we exceed 1000 picofarad, we can use Sub-multiples, "like we do with meters/kilometers". As already clarified above that:

1μF = 1000nF

1nF = 1000pF

So, we can say that our 4700pF capacitor is 4.7nF.

In this case, it is not convenient to use the micro unit because the value would not be easy to read (0.0047μF).

With larger values, such as used capacitor filters number 104, that is, 10 + 4 = 100,000 pF or also 100nF, it is common for manufacturers to use the nomenclatures written on the capacitor body 0.1μF or .1μf (point one μF) .

Practical reading of the Polyester Capacitor

100nF Capacitor, tolerance of ± 5% and maximum working voltage of 100V, Figure 5 above.

In this capacitor we have 6 alphanumeric digits, 2A104J.

The first two initial 2A digits refer to Maximum Voltage, we can use the complete EIA table codes that indicate the maximum capacitors work voltages in direct voltage (DC).

EIA Table of Code Indicators of Working Voltages of a Capacitor

0G = 4VDC	0L = 5.5VDC	0J = 6.3VDC
1A = 10VDC	1C = 16VDC	1E = 25VDC
1H = 50VDC	1J = 63VDC	1K = 80VDC
2A = 100VDC	2Q = 110VDC	2B = 125VDC
2C = 160VDC	2Z = 180VDC	2D = 200VDC
2P = 220VDC	2E = 250VDC	2F = 315VDC
2V = 350VDC	2G = 400VDC	2W = 450VDC
2H = 500VDC	2J = 630VDC	3A = 1000VDC

The next three digits refer to its capacitance, in the case as already exemplified 104 = 10 + 4 zeros, which is equal to 100,000pF = 100nF.
The last digit is the Letter "J", right after the three digits, determines the tolerance of the component.

It is interesting to note the fact that some letters correspond to "asymmetric tolerances", such as "P", that is, the component may have a capacity greater than indicated, but not less.

This type of tolerance is used with "filter" capacitors, where a value possibly higher than indicated does not minimize circuit operation, as we can see in the EIA table below.

EIA Table of Code Working Tolerance Indicators of a Capacitor

B = ± 0.10pF
C = ± 0.25pF
D = ± 0.5pF
E = ± 0.5%
F = ± 1%
G = ± 2%
H = ± 3%
J = ± 5%
K = ± 10%
M = ± 20%
N = ± 30%
P = ± +100%, - 0%
Z = ± +80%, - 20%

In the vast majority of cases, it may be useful to know the exact maximum voltage the capacitor can withstand without bursting or damaging its internal properties.

As we know, a capacitor is made up of a series of metal plates insulated from each other. This insulating material is very subtle, especially in the case of high-value capacitors.

On the other hand, if the voltage is too high, there is a risk that an electrical arc will pass through the electrical insulation between the plates, breaking it and shorting the capacitor.

For this reason, the insulating material used is designed to work up to a certain maximum voltage level, so let's look at these capacitor voltages.

Dimensions of a Voltage-Based Capacitor

Often the maximum working voltage can be found clearly written, especially on capacitors designed to work with high voltages, other times the voltage value is not directly indicated.

It often happens with capacitors used in low voltage circuits. These capacitors support voltages between 50V and 100V, well above the typical working voltages of 5V, 12V, 18V, 24V, 48V.

A super important tip when designing or analyzing a circuit and not knowing for sure the capacitor working voltage, is to take into account the size, which in this case "size is important", as we cannot work with the structure of a capacitor.

A high voltage and small size, of course there are exceptions, tantalum capacitors are altogether quite small compared to their capacitance, but as I said, "compared to their capacitance, not their voltage".

Last but not least, there is a numeric encoding used by some manufacturers which consists of a number followed by a letter. In the table of tolerances we can see the maximum working voltages.

As with everything related to technology, nothing is absolute and therefore a component manufacturer always appears, which uses systems to indicate values different from those we describe. In any case, in general terms, this article's description fits very well (sometimes with slight variations) to most commercial capacitors nowadays.