Cirrus Logic CDB5534U - Manual (Page 4)

CDB5534U
4 DS289DB6
Table 1. Voltage Reference Selection for VREF+
Table 2. Voltage Reference Selection for VREF-
1.2.2 Digital Section
Figure 2 illustrates the schematic of the digital section. It contains the microcontroller, USB interface, EE-
PROM, JTAG header, reset circuitry, and an external interface header. The microcontroller interfaces the
SPI
™
and MICROWIRE
™
compatible serial port of the CS5534 with the USB connection to the PC. Note
that the SCLK and SDI signals are level shifted to support both +3.3 V and +5 V digital operation.
The microcontroller EEPROM is used to store firmware. An external interface header, J19, is provided to
allow the CDB5534U to be interfaced with an external microcontroller. To use this serial interface, the
0 ohm resistors R9, R10, R23, and R27 should be removed to disconnect the on-board microcontroller
from the serial interface.
1.2.3 Power Supply Section
Figure 3 illustrates the power supply connections to the evaluation board. VA+ supplies the positive ana-
log supply for the CS5534 and the LT1019 reference. Header J14 allows the VA+ supply to be sourced
from either the VA+ binding post (J2), or from the +5 V binding post (J3). VA- supplies the negative analog
supply for the analog section. Header J13 allows the VA- supply to be sourced from either the VA- binding
post (J1), or connected to the board ground. Note that the VA- supply should be connected to ground
when powering the CDB5534U from a single +5 V analog supply. VD+ supplies the digital section of the
ADC and level shifters. Header J15 allows the VD+ supply to be sourced from the VD+ binding post (J5),
Reference Description J17
VA+
Selects Positive
Analog Power
Supply
LT1019
Selects on-Board
LT1019 Reference
(5ppm/ ° C)
VREF+
Selects External
Reference Source
(J12)
Reference Description J18
VA-
Selects Negative
Analog Power
Supply
GND
Selects Board
Gnd
VREF-
Selects External
Reference Source
(J12)
O O VREF+
O O VREF+
O O VREF+ VA+
LT1019
REF+
O O VREF+
O O VREF+
O O VREF+ VA+
LT1019
REF+
O O VREF+
O O VREF+
O O VREF+ VA+
LT1019
REF+
O O VREF-
O O VREF-
O O VREF- VA-
GND
REF-
O O VREF-
O O VREF-
O O VREF- VA-
GND
REF-
O O VREF-
O O VREF-
O O VREF- VA-
GND
REF-