MSP58C20 Datasheet, PDF (1/17 Pages) Texas Instruments – AUDIO-BAND CONVERTER

MSP58C20
AUDIO-BAND CONVERTER
D Analog Portion of ADC and DAC for
Audio-Band Signal-Processing
Applications
D 5-V Supply Voltage
D Oversampling Second-Order Sigma-Delta
Modulator
D 1.024-MHz Master Clock Frequency
D On-Chip Continuous-Time Antialiasing and
Smoothing Filters
D High-Performance Fully Differential and
Symmetrical Analog Data Paths
D Internal Reference Voltage and
Common-Mode Bias Voltage Generation
D Very Low Power Consumption Mode
SPSS015B – DECEMBER 1993 – REVISED JULY 1996
DW PACKAGE
(TOP VIEW)
V_SUB
1
NC
2
V_SS
3
AIP
4
AIM
5
PWAD
6
PWDA
7
ADOUT
8
NC
9
NC
10
20
NC
19
NC
18
AOP
17
AOM
16
DIGS
15
DIGL
14
ADCLK
13
V_DD
12
NC
11
NC
NC – No internal connection
description
The MSP58C20 is the analog portion of an audio-band sigma-delta analog-to-digital and digital-to-analog
converter and is a companion part to the MSP58C80. The MSP58C20 is designed to operate only with the
MSP58C80, which contains the digital portion of the audio-band converter. The circuit consists of three main
blocks: the analog-to-digital converter (ADC), the digital-to-analog converter (DAC), and internal reference and
bias voltages.
The analog-to-digital conversion chain consists of a continuous-time antialiasing stage, an analog oversampled
modulator, and the modulator bias voltage. The antialiasing stage is a second-order low-pass filter with a cutoff
frequency of typically 190 kHz. The modulator is a sigma-delta feedback loop, which oversamples the signal
at 1.024 MHz and provides second-order noise shaping. It performs the conversion of the differential analog
input signal to a pulse-density-modulated single-bit digital output (ADOUT). When a maximum positive
differential input voltage (i.e., a maximum positive voltage difference of AIP – AIM) is applied at the AIP and AIM
inputs, the resulting code at the ADOUT output is all ones.
The digital-to-analog conversion chain consists of a fast DAC, an analog low-pass filter, and the filter’s bias
voltage. The two input bits (DIGS and DIGL), sampled at 0.512 MHz from a digital modulator on the MSP58C80,
are the inputs of the DAC conversion chain. Based on the values for DIGS (the sign bit) and DIGL (the level bit),
the following table shows the DAC voltage steps that are produced.
DIGS
L
L
H
H
DIGL
L
H
L
H
DAC VOLTAGE STEPS
–1 × Vref
–2 × Vref
+1 × Vref
+2 × Vref
When DIGS = L, the AOM analog output has a more positive voltage than AOP. When DIGL = H, the absolute
value of the voltage difference between AOP and AOM is greater than when DIGL = L. A band-gap voltage
source is used to produce the DAC and ADC reference voltages. These two references are different to avoid
crosstalk between the two converters.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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Copyright © 1996, Texas Instruments Incorporated
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