CDB5541 Cirrus Logic Inc, CDB5541 Datasheet - Page 4

• Manufacturer Part Number: CDB5541
• Description: Development Kit
• Manufacturer: Cirrus Logic Inc

Specifications of CDB5541

• Silicon Manufacturer: Cirrus Logic
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: CS5541
• Features: RS-232 Serial Communication With PC, Chip Control And Data Capture, FFT Analysis
• Kit Contents: Board
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

1. HARDWARE
1.1 Introduction
The CDB5540 and CDB5541 evaluation systems
provide a quick means of testing the CS5540 and
CS5541 Analog-to-Digital Converters (ADCs).
The CS5540/41 are low-power, low-voltage ∆−Σ
analog-to-digital converters (ADC), targeted at
temperature and pressure measurement, and vari-
ous portable devices where low power consump-
tion is required.
The CDB5540/41 evaluation boards are equipped
with either a CS5540 or a CS5541 and interfaces
directly to a PC though an RS-232 serial interface.
The included analysis software allows the user to
control the various functions of the CS5540/41, as
well as capture and save data. The software also
provides data analysis tools to display the time do-
main, frequency domain, and noise histogram per-
formance for a captured set of data.
1.2 Evaluation Board Overview
The evaluation board is partitioned into two main
sections: analog and digital. The analog section
consists of the ADC and a voltage reference. The
digital section consists of the AVR microcontrol-
ler, the hardware test switches, the reset circuitry
and the RS-232 interface.
The evaluation board’s analog and digital sections
operate from a single +3.0 V power supply and in-
terface to an IBM
232 interface. The board comes equipped with an
AVR microcontroller and a 9-pin RS-232 cable
which physically interfaces the evaluation board to
the PC. The software provides a means to display
and evaluate the performance of the ADC in the
time or frequency domains.
The evaluation board supports a single supply con-
figuration. The AGND post should be connected to
0 V, and the VA+ post should be connected to 3.0
V. HDR14 is populated such that VA+ powers
4
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compatible PC through the RS-
VCC, the board logic supply voltage, and VD+, the
digital ADC supply voltage. HDR13 is populated
such that AGND, the analog ADC ground, is di-
rectly connected to DGND, GND1, and VA- (the
digital ADC ground, board logic ground, and VA-
of the ADC, respectively). All of this is represented
in Figure 7, which depicts the power supply config-
uration.
Figures 11-13 show layout plots of the evaluation
board, with the ground planes removed, so that sig-
nal traces may be seen easier. This can serve as an
aid when designing a board.
1.2.1 Analog Section
The evaluation board runs at 32.768 kHz. Howev-
er, by configuring HDR2, a variable clock may be
provided from either the microcontroller or from an
external source connected to the XOSC connector
on J5. Analog input signals can be connected to the
converter via connectors J2 (CH 1) and J12 (CH 2).
Note that a simple RC network filters the input to
reduce broadband noise.
The evaluation system provides three voltage refer-
ence options: the on-board 2.5V reference, the
power supply voltage, or an external voltage refer-
ence source, as shown in Table 2. When using an
external reference, the signal must be connected to
XREF+ and XREF- on connector J3.
A schematic of the ADC and the components di-
rectly around it, are depicted in Figure 8. A sche-
matic representation of the voltage reference
circuit, as well as the external signal connectors, is
portrayed in Figure 9.
1.2.2 Digital Section
Figure 10 represents the schematic of the digital
section of the evaluation board. It contains the mi-
crocontroller, test switches, and an RS-232 inter-
face IC. The test switches aid in debugging
communication problems between the board and
the PC. The microcontroller, which derives its
clock from a 3.684 MHz crystal, is initially config-
CDB5540 CDB5541
DS503DB1