Safety Notice
Read this before connecting a Binho Supernova, Binho Pulsar or Binho Nova to a circuit.
Key Facts
Section titled “Key Facts”- The adapters are not electrically isolated from the PC. On the Supernova and Pulsar, all power domains share one ground, and that ground connects to the host PC’s ground through the USB cable.
- Stay inside the ratings below. Stresses beyond the absolute maximum ratings may permanently damage the adapter.
- Never let the adapter and the target both power the target voltage (VTARG) pin.
Electrical Ratings
Section titled “Electrical Ratings”Supernova
Absolute maximum ratings (Supernova datasheet rev 1.6, section 6.1):
| Parameter | Min | Max |
|---|---|---|
| USB input voltage | 5.5 V | |
| USB input current | 1000 mA | |
| Operating temperature | 0 °C | 70 °C |
| ESD rating | ±4000 V | |
| I3C HV port: power domain input voltage | 5.5 V | |
| I3C HV port: power domain output current | 250 mA | |
| I3C HV port: voltage on SCL, SDA | 3.6 V | |
| I3C LV port: power domain input voltage | 2.5 V | |
| I3C LV port: power domain output current | 400 mA | |
| I3C LV port: voltage on SCL, SDA | 2.5 V | |
| Multifunction and dedicated I2C ports: power domain input voltage | 4.2 V | |
| Multifunction and dedicated I2C ports: power domain output current | 250 mA | |
| Multifunction and dedicated I2C ports: voltage on any pin | 4.2 V |
Recommended operating range for signals: 1.2–3.3 V on the I3C HV, multifunction and dedicated I2C ports; 0.8–1.2 V on the I3C LV port.
Pulsar
Absolute maximum ratings (Pulsar datasheet rev 1.3, section 6.1):
| Parameter | Min | Max |
|---|---|---|
| USB input voltage | 5.5 V | |
| USB input current | 1000 mA | |
| Operating temperature | 0 °C | 70 °C |
| ESD rating | ±4000 V | |
| RS-485 port: differential power domain output current | 250 mA | |
| RS-485 port: voltage on A, B | −15 V | +15 V |
| CAN-FD port: differential power domain output current | 250 mA | |
| CAN-FD port: voltage on CAN+, CAN− | −42 V | +42 V |
| Multifunction and dedicated I2C ports: power domain input voltage | 4.2 V | |
| Multifunction and dedicated I2C ports: power domain output current | 250 mA | |
| Multifunction and dedicated I2C ports: voltage on any pin except 1-Wire | 4.2 V | |
| Voltage on 1-Wire pin | 5.5 V |
Recommended operating range: 1.2–3.3 V on the multifunction and dedicated I2C ports (1-Wire up to 5.0 V); −7 to +12 V on RS-485 A/B; −12 to +12 V on CAN+/CAN−.
Nova
The Binho Nova uses 3.3 V logic levels on all protocols and is powered from USB (5 V). Its harness provides a 3V3 pin and a VUSB pin. See Binho Nova.
Target Voltage Warnings (Supernova and Pulsar)
Section titled “Target Voltage Warnings (Supernova and Pulsar)”- After a reboot, firmware update or DFU on 4.6.x and earlier, a rail that was saved at one voltage and later set to 0 V can come back at about 3.3 V. Disconnect a low-voltage target before rebooting or updating the adapter.
- With the rail at 0 V on 4.6.x and earlier, the I2C pull-ups stay powered and can partly power an unpowered target through SDA and SCL. Disable the pull-ups or disconnect the target first.
Ground Loops
Section titled “Ground Loops”Take care when using the host adapter in the presence of a ground loop. Ground loops are common on a test bench when the host adapter is not the only ground path between the test circuit and the host computer. A ground loop is not necessarily a problem, but it needs attention.
Common Ways a Ground Loop Can Exist:
- Other USB devices (such as programmers) are connected to the test circuit, or the test circuit itself is plugged into the USB port on the computer. In addition to the host adapter’s ground connection, the test circuit’s ground is also connected to the PC’s ground through another USB port.
- Non-isolated power supplies. Most AC power supplies with 3-prong plugs will short the MAINS earth ground pin to the power supply ground output. That includes the PC’s ground. If the test circuit is powered from a 3-prong wall power supply and the PC is also plugged in, that will form another ground path. Keep in mind that with a laptop that is not plugged in, even an attached external monitor or printer will create a ground loop.
Common Ways Damage Can Occur:
- When connecting or disconnecting wires, one of the ground signals from the host adapter is accidentally brushed against a power supply pin on the test circuit, such as +5V. If there are no other ground paths between the test circuit and the computer, nothing will happen. However, if there is a ground path, then current will flow from that voltage supply through the host adapter’s ground pin, through the USB cable and the host PC, and then through the secondary ground connection: either MAINS earth ground or another USB port, back to the ground on the test circuit. That is the same as shorting out the voltage supply on the test circuit, but it uses the host adapter and the host PC as the short circuit, which could damage all components in the loop.
- What if the test circuit’s ground reference isn’t at the same voltage as the ground loop connection? For instance, if the circuit is powered by a bipolar power supply used to produce +10 volts and -10 volts, and then the circuit uses the -10 volt rail as its ground voltage, but there exists a ground loop through MAINS earth ground to the power supply’s 0 volt output, then effectively the ground on the test circuit is actually -10 volts relative to the host PC. Connecting the host adapter will immediately short out the test circuit’s power supply and potentially damage all devices present in the loop.
Identifying if a Ground Loop is Present
Section titled “Identifying if a Ground Loop is Present”To identify a potential ground loop between the host adapter and the test circuit, check the resistance between the test circuit ground and the host adapter’s ground. While the host adapter is connected to the PC, if the resistance reads infinite on a multi-meter, then the grounds are isolated. Otherwise, they are connected, and a ground loop exists.
If a ground loop is present, extra care should be taken, as highlighted below, before connecting the host adapter ground to the test circuit ground.
If a ground loop between the test circuit and the host PC is suspected but it is uncertain whether the grounds on both sides to be used are at the same potential, a quick test with a multi-meter is available. With a resistor of about 10 kΩ, an additional test is possible.
- Connect the host adapter to the PC but not the test circuit.
- Measure the voltage between the ground pin on the host adapter and the ground pin on the test circuit.
- If there is a ground loop and the measured voltage is greater than about +/- 100mV, then a common mode ground current may occur when they are connected, damaging the equipment.
- If there is a ground loop and the measured voltage is smaller than about +/- 100mV, then it is safe to connect the ground pins.
- If there is not a ground loop or it is not certain whether there is a ground loop, then the voltage may drift significantly. If it is CERTAIN there is no ground loop, then it is safe to connect the grounds.
If it is not certain whether there is a ground loop, or to perform another test anyway, connect the resistor (about 10 kΩ) between the two grounds and then measure the voltage across the resistor.
- A voltage that indicates a noticeable current means there is a ground loop between devices. Do not connect the grounds together.
- An insignificant voltage across the resistor means either there is no ground loop or there is a ground loop, but both grounds are at the same reference. It is safe to connect the host adapter.
Identifying If The Test Circuit Is Isolated From The PC
Section titled “Identifying If The Test Circuit Is Isolated From The PC”The test circuit’s local ground is isolated from the host PC when one of the following is true:
- The test circuit is battery-powered and has no other electrical connections to the host PC or devices powered from MAINS power.
- The test circuit is powered from an isolated power supply that does NOT short MAINS earth ground to the output ground. Bench top supplies with a separate green earth ground terminal do this. USB wall adapters also do this. Common AC power adapters (chargers, “wall warts”) with 2-prong plugs are also isolated. Most power supplies do have transformers that can provide isolation if implemented properly.
- The Host PC is a laptop running from a battery or is plugged into an instrumentation isolation transformer. Normal isolation transformers connect earth ground for human safety reasons.
Using an Isolated Wall Adapter to Power the Test Circuit
Section titled “Using an Isolated Wall Adapter to Power the Test Circuit”Using isolated wall adapters such as USB wall adapters to power the test circuit will isolate its ground from MAINS ground, although that does not always eliminate ground loops. For example, if the test circuit was connected to the same computer that the host adapter is connected to, then a ground loop is formed.
Are Binho Host Adapters Safe to Use in the Presence of Ground Loops?
Section titled “Are Binho Host Adapters Safe to Use in the Presence of Ground Loops?”Yes, as long as both grounds are at the same voltage level and as long as only the host adapter ground is connected to the ground of the test circuit.