IC-TW28 Datasheet, PDF (22/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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ABZ Outputs
The iC-TW28 provides differential ABZ outputs capable
of driving 20 mA into a terminated RS422 line. The
A+, A–, B+, B–, Z+, and Z– outputs can be directly
connected to the RS422 line as shown in Figure 17.
In stand-alone applications, it is recommended to al-
ways provide for an RC network on the PC board and
only populate the capacitor if required. Without the ca-
pacitor, the resistor provides the necessary pull-up. In
applications using a host processor or microcontroller,
the xRST input is best controlled by the host.
iC-TW28
A+
A–
B+
B–
Z+
Z–
A+
120 Ω
A–
B+
120 Ω
B–
Z+
120 Ω
Z–
Figure 17: ABZ Output Connection
The three signal pairs should be terminated with a 120 Ω
resistor at the far (receiving) end of the cable as shown.
In serial configuration mode, the RS422-compatible line
driver can be disabled to save power for local or short-
-run applications. In this case, termination resistors
should not be used.
UVW Outputs
In serial configuration mode, the iC-TW28 can be con-
figured to provide differential UVW outputs or simultane-
ous single-ended ABZ and UVW outputs. See Output
Modes, Directions, and Polarities on page 56 for more
information.
xRST Input
The iC-TW28 contains a built-in power-on-reset (POR)
circuit that controls the safe start-up of the device. In
most applications, no external components are required
and xRST can be connected directly to 3.3 V.
xIRQ Output
In stand-alone applications, xIRQ functions as an ac-
tive-low fault output. It can be used to directly drive
an LED with an appropriate current-limiting resistor for
fault indication.
In hosted applications, xIRQ is connected to an interrupt
request input on the host processor or microcontroller.
In this way, when a warning or fault occurs, the host pro-
cessor can query the iC-TW28 to determine what action
to take. The xIRQ output can also be configured as an
open-drain output allowing a wired-OR connection of
multiple iC-TW28s to a single interrupt request input on
the host processor. See Chaining Multiple iC-TW28s
on page 76 for more information.
If the xIRQ output is not used, configure it for push-pull
operation so that it does not float.
LED Output
In serial configuration mode, the iC-TW28 can be con-
figured to provide LED intensity control. The LED output
functions as a high-current output to drive the illumina-
tion LED used with an optical sensor. See LED Intensity
Control on page 72 for more information.
PINCFG Input
The PINCFG input is used to select whether the
iC-TW28 is in pin configuration or serial configuration
mode. Connect PINCFG to 3.3 V to select pin config-
uration mode. Connect PINCFG to ground to select
serial configuration mode. Do not allow the PINCFG
input to float.
Alternatively, an RC network with recommended values
of 1 kΩ and 100 nF can be connected to the active-low
xRST input as shown in Figure 18. This provides a
100 µs delay and guarantees proper start-up under all
conditions. Larger resistances can be used to provide
proportionally longer delays.
DVDD
1 kΩ
100 nF
iC-TW28
xRST
Figure 18: xRST Connection