Cirrus Logic CRD5490 - Manual (Page 6)

CRD5490-Z
6 DS988RD1
2.3 Power Supply
The CRD5490-Z contains two separate power supply domains: isolated +5V USB supply and +3.3V non-isolated
CS5490 power supply derived from the power line. The +3.3V non-isolated power supply circuit is designed to
reduce the overall supply volume by creating a two-stage drop capacitor and buck supply.
By selecting an efficient buck design instead of a simple voltage regulator, the rectified supply voltage is raised, the
transferred power is increased, and the drop capacitor value is reduced. Reducing the value substantially reduces
the capacitor's size. If size is not a factor, the more expensive buck design could be replaced with a simple voltage
regulator. Figure 3 and Figure 4 show the two options evaluated for the CRD5490-Z design. Contact Cirrus Logic
sales for assistance with a cost-reduced, regulator-only design.
2.4 MCU Purpose
The CRD5490-Z is designed to minimize the requirements of the MCU. Virtually any low-cost MCU with non-volatile
memory (NVM) can be used with the CS5490 device and software. The microchip MCU has the following purposes
in the CRD5490-Z:
– Store and reload calibration coefficients
– Perform USB to UART transactions that mimic a serial COM port
USB transactions are sent from the PC to the MCU. The MCU reads the first byte (character) and determines
whether it should transmit the remaining bytes to the CS5490 as a Write/Read/DSP command or store or recall as
calibration coefficients into NVM. All responses from the CS5490 are directly translated back to the PC via the MCU.
MCU UART communication transactions can be viewed at the bottom of the GUI. Characters sent or received are
displayed in hexadecimal format. Refer to Figure 26.
AC
Drop Capacitor
and Rectifier
Buck
Converter
+35V +3.3V
CS5490
Figure 3. Power Supply Option 1
AC
Drop Capacitor
and Rectifier
+3.3V
Regulator
+6V +3.3V
CS5490
Figure 4. Power Supply Option 2