The USB 3.2 specification absorbed all prior 3.x specifications. USB 3.2 identifies three transfer rates – 20Gbps, 10Gbps, and 5Gbps. Usb 3.2 Cable,Usb Type-C Cable,5Gbps Usb Type-C Cable,10Gbps Usb Type-C Cable UCOAX , https://www.ucoax.com
Key characteristics of the USB 3.2 specification include:
Defines multi-lane operation for new USB 3.2 hosts and devices, allowing for up to two lanes of 10Gbps operation to realize a 20Gbps data transfer rate, without sacrificing cable length
Delivers compelling performance boosts to meet requirements for demanding USB storage, display, and docking applications
Continued use of existing USB physical layer data rates and encoding techniques
Minor update to hub specification to address increased performance and assure seamless transitions between single and two-lane operation
Improved data encoding for more efficient data transfer leading to higher through-put and improved I/O power efficiency
Backwards compatible with all existing USB products; will operate at lowest common speed capability
Measuring the current passing through a sense resistor might seem straightforward—amplify the voltage and read it with an ADC. But what happens when the sense resistor’s voltage differs significantly from the system's ground? That’s when things get tricky. Traditional methods involve eliminating this voltage difference either in the analog or digital domain. However, there’s an innovative alternative—wireless sensing.
Analog current sense ICs are compact and efficient, but their ability to handle high voltages is constrained by semiconductor processes. Devices capable of withstanding voltages above 100V are rare. These circuits struggle when the sense resistor’s common-mode voltage fluctuates rapidly or moves away from the system ground. Digital isolation techniques, such as magnetic or optical isolation, offer higher precision and can typically handle thousands of volts. Yet, these systems require isolated power supplies, and sometimes, long cables or wires are needed if the sense resistor is physically separated from the main system.
Wireless current sensing circumvents many of these limitations. By allowing the entire circuit to float with the sense resistor’s common-mode voltage and transmitting data wirelessly, voltage limits become irrelevant. The sense resistor can be placed virtually anywhere without needing to run lengthy wires. And if the circuit’s power consumption is minimal, a standalone power supply may not even be necessary—a tiny battery could keep it running for years.
**Design Overview**
Figure 1 presents a block diagram of the design. The current sensing circuit uses the ultra-low power chopper-stabilized operational amplifier LTC2063 to amplify the voltage drop across the sense resistor. The AD7988, a micropower SAR ADC, digitizes the value and communicates the result via the SPI interface. The LTP5901-IPM is a radio module that combines not just the radio but also the networking firmware needed to create an automatic IP mesh network.
Additionally, the LTP5901-IPM includes an onboard microprocessor that reads the SPI port of the AD7988 ADC. The LTC3335 is a low-power DC/DC converter that transforms battery voltage into a stable output. It also features a coulomb counter to track the total charge drawn from the battery.
**Signal Chain**
The LTC2063 is an ultra-low power chopper-stabilized op-amp with a maximum supply current of just 2µA, making it ideal for battery-operated devices. Its offset voltage is less than 10µV, ensuring accurate measurements of very small voltage drops. As seen in Figure 2, the LTC2063 is configured to amplify the voltage across a 10mΩ sense resistor and perform level-shifting. By selecting the appropriate gain, we map the ±10mV full-scale voltage drop (corresponding to ±1A current) to the full-scale range near the output, centered at 1.5V. This amplified signal is sent to a 16-bit SAR ADC. The AD7988 was chosen due to its extremely low standby current and excellent DC accuracy. At lower sampling rates, the ADC automatically powers down between conversions, achieving an average power consumption as low as 10µA at 1ksps. The LT6656 provides biasing, level-shifting resistors, and ADC reference inputs. Consuming less than 1µA, the LT6656 reference can deliver up to 5mA with low dropout voltage, easily producing precise 3V outputs even with a 3.3V system supply.
Three primary sources of offset error exist in this signal chain, collectively contributing approximately 0.5% error relative to the ±10mV full-scale input. These include the offset voltages of the LTC2063 and AD7988, as well as the mismatch in the level-shifting resistors (recommended at 0.1%). A single-point calibration can largely eliminate this offset. Gain errors are generally dominated by the inaccuracies of the available sense resistors, which are often less precise than the 0.05%, 10ppm/°C specifications of the LT6656 reference.
**Power Management**
The LTC3335 is a nano-power buck-boost converter with an integrated coulomb counter. Configured to generate a regulated 3.3V output from an input supply of 1.8V to 5.5V, it enables the circuit to operate from power sources like two alkaline cells. For duty-cycled wireless applications, the load current ranges from 1µA to 20mA depending on whether the radio is active or sleeping. At no load, the LTC3335’s static power consumption is only 680nA, keeping the overall circuit power consumption low when the radio and signal chain are in sleep mode. Additionally, the LTC3335 can output up to 50mA, easily providing sufficient power during radio transmission/reception, making it suitable for various signal chain circuits.
The LTC3335 also features a built-in coulomb counter, which is very convenient. During operation, it records the total charge taken from the battery. This information can be read through the I²C interface to predict when the battery needs replacement.
**Wireless Networking**
The LTP5901-IPM is a complete radio module incorporating a transceiver, an embedded microprocessor, and SmartMesh IP networking software. In this application, the LTP5901-IPM serves two functions: wireless networking and managing the microprocessor. When multiple SmartMesh IP nodes are powered on near the network manager, they automatically recognize each other and form a wireless mesh network. The entire network synchronizes automatically, meaning each radio is powered on only for a very brief, specific interval. Thus, each node not only serves as a sensor information source but also functions as a routing node to relay data from other nodes to the manager. This creates a highly reliable, low-power grid network with multiple paths from node to manager, yet all nodes—including routing nodes—consume minimal power.
The LTP5901-IPM includes an ARM Cortex-M3 microprocessor core running networking software. Users can also write custom application firmware to fulfill specific tasks. In this example, the microprocessor within the LTP5901-IPM reads the SPI port of the current measurement ADC (AD7988) and the I²C port of the coulomb counter (LTC3335). It can also put the chopper op-amp (LTC2063) into shutdown mode, reducing its power consumption from 2µA to 200nA. This conserves additional power in applications where measurement intervals are extremely long.
**Total Power Consumption**
The total power consumption of a complete application circuit depends on several factors, including how frequently the signal chain takes readings, how the node is configured in the network, and so on. For a node reporting once per second, the typical power consumption of the measurement circuit is less than 5µA, and the typical power consumption of the radio is around 40µA. A small battery can last for years.
Combining Linear Technology and Analog Devices’ signal chain, power management, and wireless networking products allows us to design truly wireless current sensing circuits. Figure 3 shows an implementation example. The LTC2063, a new ultra-low power chopper op-amp, accurately measures small voltage drops across the sense resistor. The entire circuit, including the micropower ADC and the reference, floats with the common-mode voltage of the sense resistor. Powered by a small battery, the nano-powered LTC3335 switching regulator can sustain the circuit for years while reporting cumulative battery usage via its built-in coulomb counter. The LTP5901-IPM wireless module manages the entire application and automatically connects to a highly reliable SmartMesh IP network.
In conclusion, wireless current sensing offers a revolutionary approach to current monitoring, overcoming many traditional limitations. It combines simplicity, flexibility, and reliability, making it an ideal choice for modern IoT applications.