SQID: Power 24Vdc/+3.3Vdc

24Vdc

The SQID receives 24V of power via the power connector located at P400. It is a Phoenix Contact 5.08mm connector (Phoenix PN: 1777073).

The 24V circuit is of the following form:

The 24Vdc input is converted to +3.3Vdc by an isolating DC-DC converter located at PWR400.
A compatible, mains operated, 24Vdc output power supply (MEI PN: 1022-0008) is also available upon request.

The 24V input located at P400 is protected against reverse polarity connection. Over-current protection is provided at location F400, which contains a 2A slow-blow fuse (Little fuse Part No. R251 002). This fuse should NOT be cleared under normal operation.

The 24V rails are made available for use by a board module via the Type C Connector located at J400. This is useful where a board module requires a voltage other than +3.3V (ex: the SQIO-ADC4DAC4, which generates its ±15V and +5V locally).

24Vdc could alternatively be supplied to the SQID via the Type C Connector located at J400.

The power drawn from the 24V rail varies with both the actual value of the 24V rail and also with any external load placed on the 3.3V output rail.

Input Voltage Range

The input range of the DC-DC converter is 18~36V, but to ensure reliable operation under all load conditions, here is the recommend operating range for the 24V supply.

+3.3Vdc

For normal operation of the SQID, approximately 400mA is consumed from the +3.3V rail. Since the normal output current capacity of the 5W, DC-DC converter is 1200mA (with J400 pins unloaded), an extra 800mA of current at +3.3V is available for use by other board modules.