BECKHOFF ET1100 - Manual (Page 54)

Pin Description
III-40 Slave Controller – ET1100 Hardware Description
3.10 Power Supply
The ET1100 supports different power supply and I/O voltage options with 3.3V I/O (or 5V I/O, not
recommended) and optionally single or dual power supply.
The V
CCI/O
supply voltage directly determines the I/O voltages for all inputs and outputs, i.e., with 3.3V
V
CCI/O
, the inputs are 3.3V I/O compliant and they are not 5V tolerant (V
CCI/O
has to be 5V if 5V tolerant
I/Os are required).
The core supply voltages V
CC Core
/V
CC PLL
(nom. 2.5V) are generated from V
CC I/O
by an internal LDO.
V
CC PLL
is always equal to V
CC Core
. The internal LDO cannot be switched off, it stops operating if
external supply voltage is higher than the internal LDO output voltage, thus the external supply voltage
(V
CC Core
/V
CC PLL
) has to be higher (at least 0.1V) than the internal LDO output voltage.
Using the internal LDO increases power dissipation, and power consumption for 5V I/O voltage is
significantly higher than power consumption for 3.3V I/O. It is highly recommended to use 3.3V I/O
voltage and the internal LDO for V
CC Core
/V
CC PLL
.
Voltage stabilization capacitors at all power pairs are necessary.
Table 44: Power supply options (all voltages nominal)
V
CC I/O
V
CC Core
/V
CC PLL
Input
signals Output
signals
Comment
3.3V Internal LDO
(2.5V) 3.3V only 3.3V only Single power supply, low power
dissipation
3.3V External 2.5V 3.3V only 3.3V only Dual power supply, lowest power
dissipation
Not recommended:
5V Internal LDO
(2.5V) 5V only 5V only Single power supply, highest power
dissipation
5V External 2.5V 5V only 5V only Dual power supply, high power
dissipation