UDA1341TS Просмотр технического описания (PDF) - NXP Semiconductors.

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UDA1341TS

Economy audio CODEC for MiniDisc (MD) home stereo and portable applications

NXP Semiconductors. 

NXP Semiconductors

Economy audio CODEC for MiniDisc (MD)

home stereo and portable applications

Product specification

UDA1341TS

7 FUNCTIONAL DESCRIPTION

7.1 System clock

The UDA1341TS accommodates slave mode only, this

means that in all applications the system devices must

provide the system clock. The system frequency is

selectable. The options are 256fs, 384fs or 512fs.

The system clock must be locked in frequency to the digital

interface signals.

7.2 Pin compatibility

The UDA1341TS is partially pin compatible with the

UDA1340M and UDA1344TS, making an upgrade of a

printed-circuit board from UDA1340M to UDA1341TS

easier. The pins that are compatible with the UDA1340M

are marked in Fig.3.

7.3 Analog front end

The analog front end of the UDA1341TS consists of two

stereo ADCs with a Programmable Gain Amplifier (PGA) in

channel 2. The PGA is intended to pre-amplify a

microphone signal applied to the input channel 2.

Input channel 1 has a selectable 0 or 6 dB gain stage, to

be controlled via the L3-interface. In this way, input signals

of 1 V (RMS value) or 2 V (RMS value) e.g. from a

CD source can be supported using an external resistor of

12 kΩ in series with the input channel 1. The application

modes are given in Table 1.

Table 1 Application modes using input gain stage

RESISTOR

(12 kΩ)

INPUT

GAIN

SWITCH

MAXIMUM INPUT VOLTAGE

Present 0 dB

2 V (RMS value) input signal;

note 1

Present 6 dB

1 V (RMS value) input signal

Absent

0 dB

1 V (RMS value) input signal

Absent

6 dB

0.5 V (RMS value) input signal

Note

1. If there is no need for 2 V (RMS value) input signal

support, the external resistor should not be used.

7.4 Programmable Gain Amplifier (PGA)

The PGA can be set via the L3-interface at the gain

settings: −3, 0, 3, 9, 15, 21 or 27 dB.

7.5 Analog-to-Digital Converter (ADC)

The stereo ADC of the UDA1341TS consists of two

3rd-order Sigma-Delta modulators. They have a modified

Ritchie-coder architecture in a differential switched

capacitor implementation. The over-sampling ratio is 128.

7.6 Digital Automatic Gain Control (AGC)

Input channel 2 has a digital AGC to compress the

dynamic range when a microphone signal is applied to

input channel 2. The digital AGC can be switched on and

off via the L3-interface. In the on state the AGC

compresses the dynamic range of the input signal of input

channel 2. Via the L3-interface the user can set the

parameters of the AGC: attack time, decay time and output

level. When the AGC is set off via the L3-interface, the gain

of input channel 2 can be set manually. In this case the

gain of the PGA and digital AGC are combined. The range

of the gain of the input channel 2 is from −3 to +60.5 dB in

steps of 0.5 dB.

7.7 AGC status detection

The AGCSTAT signal from the digital AGC is HIGH when

the gain level of the AGC is below 8 dB. This signal can be

used to give the PGA a new gain setting via the

L3-interface and to power e.g. a LED.

7.8 Digital mixer

The two stereo ADCs (including the AGC) can be used in

four modes:

• ADC1 only mode (for line input); input channel 2 is off

• ADC2 only mode, including PGA and digital AGC (for

microphone input); input channel 1 is off

• ADC1 + ADC2 mixer mode, including PGA and AGC

• ADC1 and ADC2 double differential mode (improved

ADC performance).

Important: In order to prevent crosstalk between the line

inputs no signal should be applied to the microphone input

in the double differential mode.

In all modes (except the double differential mode) a

reference voltage is always present at the input of the

ADC. However, in the double differential mode there is no

reference voltage present at the microphone input.

In the mixer mode, the output signals of both ADCs in

channel 1 and channel 2 (after the digital AGC) can be

mixed with coefficients that can be set via the L3-interface.

The range of the mixer coefficients is from 0 to −∞ dB in

1.5 dB steps.

2002 May 16

7

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