Electrical parameters

Current consumption
	Nominal	Max	Notes
General currents
Standby current SDM‑SIO1A Standby current SDM-SIO4A	110 µA 500 µA	150 µA 850 µA	Current after `SerialClose()` has been called
RS-232 and RS-485 current consumption (per active port)¹
Idle current	4.8 mA	6 mA	After `SerialOpen()` has been called
Idle current (receive only)	3.2 mA	4.5 mA	After `SerialOpen()` in receive-only mode
Active current (RS-232)	9.6 mA	12 mA	Active RS-232 command
Active current (RS-485)	11.7 mA	13 mA	Active RS-485 command (no termination resistors)
Line load currents
RS-232 line load	2 mA per load	–	Average expected increase in drawn current per RS-232 line connected in idle or active modes (no extra current in standby mode). Both TX and RTS are considered to be RS-232 loads.
RS-485 line load²	40 mA³	77 mA⁴	This extra current is only present when actively transmitting
¹ All currents are measured with no loads connected. For the SDM-SIO4A, the currents quoted need to be totalized to allow for the state of each active serial port. ² The RS-485 transmit pair is disabled when not transmitting in order to save power. Higher value resistors can be used to save power dependent upon the application. For many applications, especially with shorter cable runs, no load/termination resistors will be needed. ³ Single 100 Ω load between transmit lines. Two 100 Ω resistors (one on each end) is the maximum recommended loading. Removing any termination resistance should dramatically decrease current consumption during transfer of data. ⁴ The RS-485 interface is protected against short circuits via a 44 Ω resistance making this the maximum current possible even during short circuit. This resistance is part of the ESD protection circuitry and will be present at all times; it shouldn’t affect normal circuit operations. RS-485 internal circuit diagram shows the circuit in detail.

Voltage specifications
Connection	Minimum voltage¹	Nominal voltage¹	Maximum voltage¹
Power supply, +12 V connection²	7V DC	12 V DC	30 V DC

RS-232 input threshold low	0.8 V	–	–
RS-232 input threshold high	–	–	2.4 V
RS-232 input absolute maximum²	–	±15 V	±18 V
RS-232 input resistance	3 kΩ	5 kΩ	7 kΩ
RS-232 output voltage swing³	±5 V	±5.4 V	–
RS-485 input (differential)	200 mV⁴	–	6 V
RS-485 output (differential)	1.5 V (at 50 Ohms)	–	–

SDM lines (high level)	4.5 V	5 V	5.5 V
SDM lines (low level)	0 V	–	0.7 V
¹ Voltage values are DC. ² It is NOT recommended that the user run their SDM‑SIO1A at maximum ratings for extended periods of time. ³ Assuming a worst case 3 kΩ load. ⁴ It is not recommended that the user allows such low input voltages as there will be an increased chance that external noise may cause errors in the incoming data.

Compliance:

View EU Declaration of Conformity document at: