DIO2186

Version 1.0, Apr 2026

www.dioo.com

© 2026 Dioo Microcircuits Co., Ltd. Jiangsu

10

swing to GND, VZL.

For devices lacking a dedicated REF pin, the VREF value is assumed to be zero. Under normal operating

conditions, the device generates an output voltage that represents the amplified differential voltage

between IN+ and IN– terminals, offset by the voltage applied to the REF pin.

8.8.2. REF connection

The device’s configuration allows current monitoring in either unidirectional or bidirectional applications,

determined by the REF pin connection.

There are different methods for REF connection.

By connecting the REF pin to ground, the output is set to ground when no current is flowing. This is the

most common unidirectional case. In unidirectional case, the output voltage remains close to ground in the

absence of current flow. When current passes from the bus supply to the load, the differential input voltage

between IN+ and IN– rises, so the output voltage at the OUT pin increases, too.

Under zero input conditions, the linear operating range of the output stage is constrained by the minimum

output voltage achievable near ground. The DIO2186’s zero current output voltage is very low, so in most

unidirectional applications, the REF pin is simply connected to ground. However, the measured current

multiplied by the current sense resistor and device gain is smaller than the zero current output voltage, the

REF pin should be biased to an appropriate voltage level above this zero current output to ensure the

output stays within the device’s linear range. To reduce common-mode rejection errors, it is advisable to

buffer the reference voltage applied to the REF pin.

Another application of the REF pin in unidirectional operation is to level-shift the output voltage. It is shown

below that a scenario where the device ground (GND) is set to a negative voltage, enabling measurement

of currents biased to negative supplies, such as those found in optical networking cards. The DIO2186’s

GND can be connected to negative voltages provided that the input voltages remain within the

common-mode range specification and the voltage difference between VS and GND does not exceed 6 V.

In this setup, the DIO2186 output is connected to a positively biased analog-to-digital converter (ADC). By

grounding the REF pin, the output voltage stays positive, protecting the ADC from potential damage. To

ensure the output voltage never falls below ground, the power supply must be sequenced such that the

positive supply powers up before the negative supply.

Figure 10. Using the REF pin to level-shift output voltage