Introduction
1-3
Introduction
The power connector (J6) carries the power supplies. The ADS1244/45EVM
requires a +5V analog supply and either a +5V or +3.3V digital supply. The
board is designed using a single ground net connected to DGND. An AGND
pin is also provided, and it can be connected to DGND using jumper J2.
The ADS1244/45 uses separate supplies for its analog and digital sections.
A jumper is inserted in each supply line. These jumpers allow the current of
each supply to be measured independently.
Four loop−style testpoints provide easy access to the ADS1244/45 clock and
the power supplies on the board. Other signals can be probed using the I/O
connector pins.
1.4
Controls
The ADS1244/45EVM is configured using four slide switches and a jumper.
Switch S1 selects the system clock source for the ADS1244. You can select
from the 4.9152MHz clock source, the 2.4576MHz clock source, or an exter-
nally provided clock. When the external clock is selected, the onboard oscilla-
tor is disabled to save power and prevent interference.
Switch S2 selects the input signal provided to the ADS1244/45. Normally you
will use the external input, but you can also use the switch to short the inputs
together and to connect the reference voltage to the inputs. The latter two posi-
tions are useful for conducting noise tests.
Switch S3 selects the reference input. One position selects the external refer-
ence input pins on the analog connector (J1). The other two positions connect
the o2.5V reference in one of two ways: between ground and the ref-
erence, or between the reference and the analog supply.
Switch S5 is used to select one of two digital power supply pins provided on
the power connector. One pin is used for +3.3V, and the other is used for +5V;
some motherboards, such as the HPA449, provide both voltages. This switch
determines the logic levels that the ADS1244/45 will use to communicate, so
it is important to set it correctly.
