. Author - Kargal.

general information

USB connectors for connecting gadgets

In recent years, there has been a noticeable tendency to unify the data/power connectors of different gadgets from different manufacturers (perhaps only Apple continues to go its own way).
In order to minimize the size, mini-USB or micro-USB connectors are used, each having five contacts and the same pinout.

The pinout of connectors and cable connection options are shown in the table ▼

Pin#	1 VBUS	2 D−	3 D+	4 ID	5 GND
Color wires	------	------	------	------ None	------
	Red	White	Green		Black
Data cable	+5V input	-Data	+Data	NC	GND
OTG —cable	+5V output	-Data	+Data	connected→ GND
Memory "DVR"	NC	NC	NC	+5V input	GND
"Garmin"	+5V input	-Data	+Data	18 kΩ→ GND
Memory "Motorola"	+5V input	NC	NC	200 kΩ→ GND
Charger "Glofish"	+5V input	NC	NC	connected→ GND

Two cables correspond to the main USB standard:

• "Data cable"- used for charging and information connection to a PC in “Slave” mode; in this cable pin4 is not connected to anything (NC - not connected).

#) In all charging (non-OTG) cases of the data bus ( D− And D+) are used in two ways - within ~2 seconds after the appearance of the external supply voltage on pin1, the gadget determines the potentials and properties of the data lines. The gadget needs to “know” the type of charging port to determine the maximum permissible current for a given charger (hereinafter referred to as the charger). After identifying the port, the gadget allows itself to consume current for operation/charging, and if the port turns out to be a signal port (types SDP or CDP), then also exchange data as a USB peripheral (Slave) device.

• "OTG cable"- the connection between pin4 (the “Ident” input) and pin5 (GND) is usually made directly in the cable part of the connector and forces the gadget to operate in “Host” mode - to power and service the connected peripherals (mouse, flash drive, external keyboard, etc. ). This cable does not allow external power supply or charging of a gadget that has USB-OTG mode. The BCv1.2 standard allows for charging in Host mode a USB-OTG device that recognizes the port type ACA(no longer with this cable), but nothing is known about the existence of such devices in nature.

Taking advantage of the laxity of compliance with the standard, many gadget manufacturers indulge in some pranks using connector contacts without notifying users. This circumstance makes it difficult to replace the standard charger with a universal one in case of loss/breakage of the standard charger or when organizing an additional charging station. For example:

• "DVR memory"- there are many models of car DVRs, which can be powered in two ways:
  1. When connected with a standard data cable, the recorder “comes to life”, but does not start recording, but offers long boring conversations (through the menu, using buttons) to explain to the recorder what is now required of it.
  2. When connected with a special “DVR memory” cable (+5 V power is supplied to pin4), such a recorder immediately starts recording, which allows you to organize its automatic switching on in the car when the engine starts.
• "Garmin", "Motorola charger"- pin4 is connected to pin5 (GND) through a resistor, the value of which sets the gadget’s operating/charging mode (see article “”).
• "ZU Glofish"(and the successors of Glofish) - pin4 is short-circuited to pin5 (GND) to allow consumption of more than 0.5 A (see topic on the 4PDA forum).

Unfortunately, there is no easily accessible information on such tricks in relation to specific models of gadgets - manufacturers are either being cunning to protect their business, or are embarrassed by their perversions. There are only scattered and not very clear mentions on the forums. We can only hope that the user community will mobilize and create a database.

Custom characteristics of chargers (chargers)

Voltage

Chargers with USB connectors for connecting the load are rated at U out = 5 V and usually actually correspond to the USB specification - U out = 4.75 ÷ 5.25 V. (Although there are ).

Typical circuit of the low-voltage part of a high-quality network charger ▼

Here HL is the feedback optocoupler LED, DA is a parallel stabilizer, actually used in comparator mode. The complete circuit seeks to set the output voltage U out such that the voltage at the output of the divider R U /R L is equal to the internal reference voltage U ref of the regulator DA. For stabilizers of the TL431 family U ref = 2.5 V, for the TL family V 431 – U ref =1.25 V. The value of U ref can actually be measured with a digital voltmeter at turned on

#) Carefully! Primary side under high voltage.

To increase U out by ~10%, it is necessary to change the parameters of the R U / R L divider so that the voltage at its output (the connection point between R U and R L) is equal to U ref not at 5.0 V at the output of the charger, but at ~5.5 V. The easiest way to do this is by adding a shunt resistor R L -Ш. Its value should be:

For U ref =2.5 V: R L-Ш =5*R L ;

For U ref =1.25 V: R L-Ш =7.5*R L ;

(The value of R L in a specific memory can be determined by its marking or actually measured with a digital ohmmeter on turned off memory and disabled load).

#) For poking around in the internals of the charger, it would be nice to have a collapsible (not glued) case.

Automotive memory (ASU)

In automotive chargers, step-down (Buck, StepDown) PWM converters are usually used. Typical output part of the circuit ▼

Here:
S.W.- output of the built-in power switch of the converter;
C BS- voltage booster capacity, used only for converters with N-MOS (or NPN) power switch;
VD1 - clamping (fixing) diode, used only for simple (non-synchronous) converters;
C COR– feedback correction capacitance (may not be used);
R U And R L- the initial feedback divider, which sets the output voltage;
R L-SH- correction resistor added for increase output voltage.

The complete circuit seeks to set the output voltage U out such that the voltage at the output of the divider R U / R L is equal to the internal reference voltage U FB of the stabilizer.

The value of U FB can be taken from the data-sheet of the converter used or actually measured with a digital voltmeter on turned on and a loaded memory, through a 50÷100 kΩ resistor (to ensure the stability of the circuit during measurement).

To increase U out by ~10%, it is necessary to change the parameters of the divider R U /R L so that the voltage at its output (the connection point between R U and R L) is equal to U FB not at 5.0 V at the output of the charger, but at ~5.5 V. The easiest way to do this is by adding a shunt resistor R L -Ш. Its value should be:

For U FB =1.23 V: R L -Ш =7.5*R L - for converters MC34063, LM2576, LM2596, ACT4070;

For U FB =0.925 V: R L -Ш =8.2*R L - for converters CX8505, RT8272, AP6503, MP2307;

For U FB =0.80 V: R L -Ш =8.4*R L - for converters AX4102, XL4005.

(The value of R L can be determined by its marking or actually measured with a digital ohmmeter on turned off memory and disabled load).

To reduce U out, the easiest way is to shunt R U.

Electronics gadgets

Charge controllers

OZ8555/o2micro

(Used in tablets based on RK3066 – Hyundai Hold X700, Window N101/YUANDAO N101; PIPO M1, PIPO Max-M8 pro, PIPO Smart-S2; CUBE U9GT3)

Contains a DC/DC converter for charging the battery and powering the gadget. Requires external power supply voltage 5.5÷5.9 V (at least 5.4 V at the input to the gadget) and is used in gadgets with a separate (non-USB) charging connector.

I didn’t find a data-sheet on the OZ8555, but it seems that its threshold for protection against insufficient supply voltage UVLO (Under Voltage Lock Out) is 5.1÷5.3 V instead of the usual 3.9÷4.5 V for 5-volt gadgets. This property would completely explain Incorrect operation from a “foreign” charger delivering less than 5.4 V.

Discussion: 33 comments

Hello.

I have a 0.6mm diameter cable, two wires, about 6-8 meters long, laid in my wall from the shield. I decided to hang the tablet on the wall and use this cable for charging. But judging by the ampere application, when the screen is on, the charge current jumps from 600 to 200mA, the average is 250-300. However, the tablet does not charge, even with the screen turned off. I tried all the charges, the result is the same. By the way, at the end of the cable at the USB connector on the tablet side, I made a date + and - jumper, before this the tablet did not detect charging at all. Next, I measured the resistance by closing the circuit from one side of the tablet - it turned out to be about 3.5-4 ohms, this is both wires back and forth if you close and measure on the other side. Quite a lot, apparently because of this the voltage drops. I measured the voltage under load in the shield (there is a twist there) - 4.7V, while without load at the end of the tablet it was 5.15V. I can’t measure it under load on the tablet.
And now, actually, the question is - if I understand physics correctly, then to increase the current I need to increase the voltage on the power supply, volts to 6-6.5, so that minus losses it reaches 5.2, -5.4 V, do you think such a trick will work?

Good day. Thank you very much for the site.

Have you found any information on the operating principle/identification of QuickCharge 2.0-3.0?

And what if a device that supports such charging is stupidly given 9 or 12 volts per USB port? What do you think the reaction will be?

I tried applying 4.9 to 6 volts to the Sony Xperia X phone. The current consumption in amperes does not change. I'm afraid to apply more than 6 volts.)

Answer

1. I have not encountered or experimented with this matter in practice.

   Answer

How to Avoid USB Port Damage

Often laptop manufacturers, and then the sellers who sell these products, give a decent warranty on the hardware they offer, with just one caveat: the warranty does not apply to USB ports. Why? Presumably, because this is the most vulnerable spot of the computer, and inexperienced users, of whom the majority are, can easily damage it as a result of improper use of the USB interface. Of course, developers are struggling with this problem and using different protective measures in different laptop models. But until the problem is finally resolved and in order to avoid trouble, users are advised to adhere to certain rules. The same applies to desktop computers.

All failures of using a USB port can be divided into software and hardware, that is, physical. Software failures are easier to fix. At least they will not require material costs, although they may take quite some time. In this case, it may be necessary to update or select a driver, configure the BIOS, and in difficult cases, reinstall the operating system. Physical malfunctions will require disassembling the computer, searching for and replacing burnt out parts, and the most unpleasant thing is replacing an expensive controller chip, which only a service center specialist can handle.

USB Energy Parameters

The most common option today is USB 2.0 connectors built into computer equipment. Less common are USB 1.1 versions, which began the widespread introduction of this type of interface at the end of the last century. The more advanced USB 2.0 began to be used in 2000; starting in 2008, USB 3.0 was released. Let's consider only the energy parameters of common ports.

The USB version 2.0 port, like the newer version 3.0, has special contacts that output a voltage of 5 V. This voltage is usually used to power external devices connected to the computer, controlled through the port, and also as a DC power source. Such a source can power a USB flashlight, a small audio system, or serve to charge a mobile phone battery.

However, the port's energy capabilities are not unlimited. The standard current it can provide is as follows. For a USB 2.0 port, the output current cannot exceed 500 mA, for a USB 3.0 version - 900 mA. When a slight overload occurs, it leads to a voltage sag, which can cause the connected device to malfunction. If the overload increases, the voltage decreases even more. In this case, there is no need to talk about the operation of the device, and the port itself may fail as a result of severe overheating of the circuit elements. Moreover, irreparable harm can be caused by a short circuit of the power buses, which will cause the burnout of the port’s protective elements.

What and how to connect to the USB 2.0 connector

Each computer can have from 2 to 6 USB ports installed, and even more on special order. Anything connected to each should not draw more than 500 mA of current. This guarantees the normal operation of the devices and the preservation of the functionality of the port itself. Low-power and serviceable loads, such as flash drives, a mouse, a keyboard or a web camera, cannot harm the interface. Powerful loads should be treated with care.

An example of a powerful load would be an external hard drive and other devices with a current consumption of 500 milliamps or more. Often such devices are equipped with two connectors connected in parallel in order to use two different USB 2.0 ports to connect them. The load capacity of this power supply method will increase to 1000 mA. Sometimes an external device has its own power source, then the port's electrical energy is not consumed at all, and it will operate in a lightweight mode.

Everything that was said here regarding the USB 2.0 port is also true for its 3.0 version, with the only difference being that instead of a maximum load current of 500 mA, it has a limit of 900 mA.

Errors when connecting powerful loads

One of the mistakes is as follows. Let's say the connected device (external hard drive) has two paired USB connectors. One of them is the main one, having a power line and a data line, the other is additional, equipped only with conductors for power. Often, due to inexperience or forgetfulness, the consumer can use only one main connector, leaving the additional connector unconnected. If the device draws 800 mA current, it will overload the USB 2.0 port, causing it to fail.

A similar situation can arise when the user uses a passive USB interface splitter - a device that increases the number of USB sockets. Such a device is designed to connect an appropriate number of low-power loads and cannot in any way increase the maximum current of the source port. If the consumer did not understand this and caused an overload through powerful loads, then troubles should be expected.

Consequences of port failure due to overload

To prevent an overload or short circuit of the power supply bus of the USB port from leading to more serious damage to the computer, developers build in special protection measures. For example, a fuse, a current limiting resistor, a self-resetting fuse. In each case, the consequences may be different.

If the fuse blows, the power supply to the port is turned off and it becomes inoperable. When a limiting resistor (usually an SMD chip) is overloaded, it becomes very hot, part of its resistive layer burns out, causing the resistance to increase, and therefore the load current decreases even more. Such a “fried” port will only be able to function with low-power loads.

If a self-resetting fuse is built into the circuit, then after removing the excessive load, the functionality of the port will be automatically restored. In other cases, you will need to disassemble the computer and replace failed elements.

Let us remind you that Serty-Service specialists are ready to help

if you have problems with USB devices.

After reading many sources, I found the same information everywhere: the USB 2.0 port is capable of delivering no more than 500mA, providing power of no more than 2.5W. However, some things cast doubt on this.

First of all, about useful things. If you select the “USB Root Hub” properties in the device manager (I don’t remember how it is in Russian, look at all devices), then the second tab “Power” will display information about the connected device: how many milliamps it requires. The value is taken from the filling of the connected device, this is not the actual current consumption:
- some flash drives require 500mA (Kingston, Transcend), and some require 200mA (Toshiba). Moreover, it has been experimentally proven that a Toshiba flash drive works on any 1.8 meter USB extension cable, even those not made to the standard. It turns out that the less a device consumes, the more chances it has to make money on a USB extension cable or low-quality front connectors of the case;
- and indeed: an optical mouse that consumes 100mA works without problems on a 3-meter USB extension cable (and all the flash drives there are already “bye-bye”);
- the USB A-B cable going to the printer reflected the recommended value of 98mA;
- USB-HDD "Silicon Power" 320GB showed a value of 2mA (connected to one USB port and functioning successfully). The reason was found out: only 1 byte is allocated for the value of milliamps in the OS, and the maximum value of this counter is 255. Each counter value is equal to 2mA. This means that the USB-HDD has gone beyond the possible maximum number, and the counter has reset to zero +1 (corresponding to the number 514mA or 1026mA). But this is more than the 500mA stated in the standard!

This was the first doubt about the truth of I max = 500mA for the USB port.
Second: one hub serves several USB ports at once, and it is written that the maximum is 500mA per port. This means, in my case, the hub is capable of delivering 2.5A (since it is responsible for 5 ports). If it is capable of delivering a total of 2.5A, what should stop it from issuing, for example, 2.5A to one port, and simply blocking the other 4.
Third: the power supply data of the disassembled USB-HDD is 5V/0.85A. This is already more than 0.5mA. Moreover, it was experimentally found that starting the HDD (reactive load) requires much more current than indicated on the HDD.
Fourth: I powered the router via a USB cable, and even then I somehow knew about the value of 1200mA. Here it is, the struggle of paradigms: heard there, seen here, said there, written here...

All the prerequisites for the experiment are there to obtain real numbers of current strength of this HDD. Over the course of a month, I will crash into the USB A-miniB cable with a high-precision ammeter for 20,000 rubles - and take readings from it. With your eyes or telemetry - whatever happens.

(added 04/07/2015): The experiment with the USB connector was successful, and my guesses were confirmed. The following equipment was used:
- multimeter DT838 (here’s a “high-precision” one for you...);
- active load: external HDD Samsung Momentus ST320LM001, USB coffee heater Orient W1002B;
- passive load: 4 resistors C5-16V-8W 1Ohm ±1%;
- USB plug;
- EliteGroup G31T-M7 and Gigabyte C51-MCP51 motherboards.

In the process of connecting the active load separately and in parallel, it became known:
- the maximum current for HDD (0.85A) is extremely accurate, it was obtained when spinning up the disk and during its initialization after loading Windows (fractions of a second). Current in idle mode: 0.28-0.35A, in transfer mode at a speed of 28MB/s: 0.56-0.63A;
- the heater consumes a constant 0.6A, including during start-up: there is no reactive load. A coffee warmer with a power of only 3W cannot be considered a serious household item;
- when connecting the load in parallel, it was possible to obtain a value of 1.19A. This value exceeds that stated in the USB 2.0 standard by 2.38 times.

Then the question arose: what is the correct limit? An inexperienced technician caused a short circuit when I entrusted him with the issue of soldering, but the equipment was not damaged, and the short circuit was not in vain: the ammeter recorded a constant passage of 3.3A through it, which means there is some kind of ampere limiter in the motherboard (for example, in the controller). Moreover, the restriction also worked when the PC was turned off.

To avoid damaging the active load, it was decided to abandon it in favor of a passive one, which transfers all the energy into its own heating: resistors. Oddly enough, high-power and low-resistance resistors were in short supply, and only 4 were found. Moreover, they are 25-30 years old, and the shelf life of this type is 15 years. What a surprise it was when, after finishing the experiments, it turned out that the resistance of one of them increased by +50%, to 1.5 Ohm. Then all the “errors” in the experiment became clear.

First, 1.45A was obtained, which successfully heated the resistors for several minutes. Further, lowering the resistance, a current value of 3.05A was achieved. And it was at this value that the automation (motherboard or Windows?) disconnected the USB connector, but in some unusual way: by reducing the current value not to 0, but to 0.4A.

So, the current limit for the USB connector hangs in the range )