User's Manual l MBa335x UM 0202 l © 2018, TQ-Systems GmbH
Page 16
4.1.9
Power supply
Illustration 10:
Block diagram power supply
The MBa335x is supplied with 24 V via X26 or X27. From this voltage 1.5 V, 3.3 V, 5 V and 12 V are generated on the MBa335x.
These voltages are used to supply the components on the MBa335x.
Additionally, 3.3 V, 5 V and 12 V are available at all three headers X4, X5 and X6 on the MBa335x.
All three connectors share the available power (3.3 V / 2 A, 5 V / 2 A, 12 V / 3 A).
1.5 V is only available at the PCIe connector X22. The 1.5 V rail can supply a maximum of 0.375 A.
The MBa335x supply is only switched on by 3.3 V when the TQMa335x power supply is up completely to avoid cross supply by
the MBa335x. Hence, the circuitry with the Power-FET as a switch for VCC3V3 should also be used in customer designs.
Attention:
In the own design, the VCC3V3 should be switched on or off with the signal VDDSHV3V3 from the
TQMa335x, to avoid cross supply and errors in the power-up/down sequence.
On the MBa335x the input voltage of 24 V has the following protective circuitry (see also Illustration 10):
•
Fuse
•
Excess voltage protection diode
•
PI filter
•
Inverse-polarity protection
•
Capacitors for voltage smoothing
