CS4215 datasheet(8/52 Pages) CIRRUS

8 / 52 page

FUNCTIONAL DESCRIPTION

Overview

The CS4215 has two channels of 16-bit analog-

to-digital conversion and two channels of 16-bit

digital-to-analog conversion. Both the ADCs and

the DACs are delta-sigma converters. The ADC

inputs have adjustable input gain, while the DAC

outputs have adjustable output attenuation. Spe-

cial features include a separate microphone input

with a 20 dB programmable gain block, an op-

tional 8-bit

µ-law or A-law encoder/decoder, pins

for two crystals to set alternative sample rates,

direct headphone drive and mono speaker drive.

Control for the functions available on the

CS4215, as well as the audio data, are communi-

cated to the device over a serial interface.

Separate pins for input and output data are pro-

vided, allowing concurrent writing to and

reading from the device. Data must be con-

tinually written for proper operation. Multiple

CS4215 devices may be attached to the same

data lines.

Analog Inputs

Figure 1, the recommended connection diagram,

shows examples of the external analog circuitry

recommended around the CS4215. An internal

multiplexer selects between line level inputs and

microphone level inputs.

Input filters using a 150

Ω resistor and a .01 µF

NPO capacitor to ground are required to isolate

the input op-amps from, and provide a charge re-

serve for, the switched-capacitor input of the

codec.

The RC values may be safely changed

by a factor of two.

The HPF bit in Control Time Slot 2 provides a

high pass filter that will reduce DC offset on the

analog inputs.

Using the high pass filter will

cause slight distortions at very low frequencies.

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 0.1uF capacitor. This prevents any DC

current flow.

Line Level Inputs

LINL and LINR are the line level input pins.

These pins are internally biased to the CMOUT

voltage. Figure 2 shows a dual op-amp buffer

which combines level shifting with a gain of 0.5

to attenuate the standard line level of 2 Vrms to

LINR

(pin 16)

LINL

(pin 18)

Line In

Right

Line In

Left

0.01 uF

NPO

0.01 uF

NPO

150

0.47 uF

Figure 3. AC Coupled Input.

56 pF

10 k

20 k

10 k

56 pF

5 k

20 k

Line In

Right

Left

CMOUT

LINR

LINL

Op-amps are run

from VA1, VA2 and

AGND.

0.47 uF

150

0.01 uF

NPO

0.47 uF

0.01 uF

NPO

150

0.47 uF

(pin 16)

(pin 18)

(pin 19)

Example

Op-Amps

are

LT1013

Figure 2. DC Coupled Input.

CS4215

DS76F2

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