Cirrus Logic CDB5566 - Manual (Page 6)

CDB5566
6 DS806DB3
3. HARDWARE DESCRIPTION
3.1 Absolute Maximum Ratings
Observe the following limits to ensure the CDB5566 component ratings are not exceeded.
• CS5566
– The absolute maximum supply voltage that can be applied to the +3.3V power supply
connection is +3.6V.
– The absolute maximum power supply voltage that can be applied between pins VL and V1-
is 6.1 V.
• LMP7732
– The absolute maximum power supply voltage that can be applied between the +2.5V and
-2.5V power supply connections is +5.5V.
3.2 Power Supply
Power supply connections and requirements are specified in Table 1. below.
Important: It is recommended that all power supplies be isolated from utility ground to prevent the intro-
duction of a ground loop. One ground connection may already exist through the serial port connection to
utility ground. Using the Cirrus Logic CapturePlus II system simplifies making connections to the
CDB5566 by providing electrical isolation between the two.
Using twisted/shielded wire will reduce electrical noise induced onto the power supply cables.
Power supplies are to be adequately regulated and sufficiently low noise to meet the application require-
ments.
3.3 Analog Section
3.3.1 Analog Input Buffers
The analog input signal connections to the input buffers are made at the INPUT A andINPUT B connec-
tors, as specified in Table 2.
There are two analog input channels on the evaluation board. Each analog input channel consists of
two low-noise amplifiers configured as unity gain non-inverting buffers. The buffers utilize two National
Semiconductor LMP7732 precision, low-noise, low-voltage, dual op-amps. These op-amps enable both
the inputs and outputs of the analog input buffer to operate virtually rail to rail. The channel input imped-
ance is 50 Ohms.
Table 1. Power Supply Connections
Power Supply
Requirement
Power Supply
Connection
Associated
Ground Return
Associated
Test Points
+2.5 V DC, ±5%, <50 mA E5 E3 TP2, TP1 (GND)
-2.5 V DC, ±5%, <50 mA E9 E7 TP4, TP3 (GND)
+3.3 V DC, ±5%, <50 mA E16 E13 TP6, TP5 (GND)
Table 2. Analog Input Connections
Channel
Analog Input
Connection
Differential Input Signal
Voltage Range Impedance
INPUT A J4 -4.096 V to +4.096 V 50 Ohms
INPUT B J5 -4.096 V to +4.096 V 50 Ohms