CS4216 datasheet(9/58 Pages) CIRRUS

9 / 58 page

OVERVIEW

The CS4216 contains two analog-to-digital con-

verters, two digital-to-analog converters,

adjustable input gain, and adjustable output level

control. Since the converters contain all the re-

quired filters in digital or sampled analog form,

the filters’ frequency responses track the sample

rate of the CS4216. Only a single-pole RC filter

is required on the analog inputs and outputs. The

RC filter acts as a charge reserve for the

switched-capacitor input and buffers op-amps

from a switched-capacitor load. Communication

with the CS4216 is via a serial port, with sepa-

rate pins for data into the device, and data from

the device. The filters and converters operate

over a sample rate range of 4 kHz to 50 kHz.

FUNCTIONAL SPECIFICATIONS

Analog Inputs and Outputs

Figure 1 illustrates the suggested connection dia-

gram to obtain full performance from the

CS4216. The line level inputs, LIN1 or LIN2

and RIN1 or RIN2, are selected by an internal

input multiplexer. This multiplexer is a source

selector and is not designed for switching be-

tween inputs at the sample rate.

Unused analog inputs that are not selected have

a very high input impedance, so they may be

tied to AGND directly.

Unused analog inputs

that are selected should be tied to AGND

through a 0.1

µF capacitor. This prevents any

DC current flow.

The analog inputs are single-ended and inter-

nally biased to the REFBUF voltage (nominally

2.2 V). The REFBUF output pin can be used to

level shift an input signal centered around

0 Volts as shown in Figure 2. The input buffers

shown have a gain of 0.5, yielding a full scale

input sensitivity of 2 Vrms with the CS4216 pro-

grammable gain set to 0. If the source imped-

ance is very low, then the inputs can be AC

coupled with a series 0.47

µF capacitor, elimi-

nating the need for external op-amps (see Figure

3). However, the use of AC coupling capacitors

will increase DC offset at 0dB gain (see Analog

Characteristics Table).

The analog outputs are also single-ended and

centered around the REFBUF pin. AC coupling

capacitors of >1

µF are recommended.

Line In

Right

Example

Op-Amps

are

MC34072

LT1013

Line In

Left

Op-amps are run

from VA+5V and

AGND

RINx

(PLCC pin 25 or 26)

REFBUF

LINx

(PLCC pin 27 or 28)

56 pF

10 k

20 k

0.47 uF

0.47 uF 20 k

150

5 k

56 pF

10 k

150

0.01 uF

NPO

0.01 uF

NPO

Figure 2. DC Coupled Input.

Line In

Right

Line In

Left

0.01 uF

NPO

0.01 uF

NPO

150

0.47 uF

RINx

(PLCC pin 25 or 26)

LINx

(PLCC pin 27 or 28)

Figure 3. AC Coupled Input

CS4216

DS83F2

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