CDB5490U
10
DS923DB5
1.4.2
Interface to Microcontroller
Interface headers J17 and J19 are provided to allow the CDB5490U to be connected to an external energy
registration device or an external microcontroller. Interface header J17 provides direct access to the
CS5490 pins while interface header J19 provides an isolated connection. It is imperative to use the iso-
lated connection (J19) when high-voltage signals are used. Failure to use isolation can result in damage
to components or electrical shock. Refer to section 1.4.3
for details on signal isolation.
Interface header J19 can be used to connect to the external microcontroller. To connect the CS5490 to
an external microcontroller, R37, R42, and R43 must be removed from the board.
1.4.3
Digital Isolation
Two types of isolation are provided: a low-speed optical coupler and high-speed digital isolation for UART
communication. Default jumper settings provide high-speed digital isolators. To enable high-speed digital
isolators, place jumpers (J18 and J20) in the RX-to-DIGITAL position and TX-to-DIGITAL position. To en-
able the high-speed digital isolators, it is also necessary to install jumper (J50) in the VDDA position. To
enable the low-speed optical UART communication, place jumpers (J18 and J20) in the RX-to-OPTICAL
position and TX-to-OPTICAL position.
The high-speed digital isolators operate from DC to 150Mbps. The low-speed optical couplers operate to
a maximum speed of about 4.8kHz. All the signals supplied to the isolators are available to the MCU.
1.4.4
Additional Device Pin Access
The CS5490's digital output pin (DO) is routed to a LED, which provides a simple visual check of the digital
output. Jumper J39 is equipped at the factory to enable the LED. The DO digital output pin is supplied to
the digital isolation using jumper J49.
The MODE pin jumper (J15) should be installed in the
VDDA to MODE
position.
The CS5490 system clock can be connected to an onboard quartz crystal, or an external clock can be
supplied to the CS5490 XIN pin though jumper J48. To connect the onboard quartz crystal, install jumper
J43 in the
XIN to CRYSTAL
position. To connect XIN to an external clock, install jumper J43 in the XIN to
XIN_EXT position.
