CS5521 datasheet(13/56 Pages) CIRRUS

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CS5521/22/23/24/28

DS317F8

1. GENERAL DESCRIPTION

The CS5521/22/23/24/28 are highly integrated

ΔΣ

Analog-to-Digital Converters (ADCs) which use

charge-balance

techniques

achieve

16-bit

(CS5521/23) and 24-bit (CS5522/24/28) perfor-

mance. The ADCs come as either two-channel

(CS5521/22), four-channel (CS5523/24), or eight-

channel (CS5528) devices, and include a low input

current, chopper-stabilized instrumentation ampli-

fier. To permit selectable input spans of 25 mV,

55 mV, 100 mV, 1 V, 2.5 V, and 5 V, the ADCs in-

clude a PGA (programmable gain amplifier). To

accommodate ground-based thermocouple applica-

tions, the devices include a CPD (Charge Pump

Drive) which provides a negative bias voltage to

the on-chip amplifiers.

These devices also include a fourth order DS mod-

ulator followed by a digital filter which provides

eight selectable output word rates of 1.88 Sps,

3.76 Sps, 7.51 Sps, 15 Sps, 30 Sps, 61.6 Sps,

84.5 Sps, and 101.1 Sps (XIN = 32.768 kHz). The

devices are capable of producing output update

rates up to 617 Sps when a 200 kHz clock is used

(CS5522/24/28) or up to 401 Sps using a 130 kHz

clock (CS5521/23). Further note that the digital fil-

ters are designed to settle to full accuracy within

one conversion cycle and simultaneously reject

both 50 Hz and 60 Hz interference when operated

at word rates below 30 Sps (assuming a XIN clock

frequency of 32.768 kHz).

To ease communication between the ADCs and a

micro-controller, the converters include an easy to

use three-wire serial interface which is SPI™ and

Microwire™ compatible.

1.1 Analog Input

Figure 4 illustrates a block diagram of the analog in-

put signal path inside the CS5521/22/23/24/28. The

front end consists of a multiplexer (break before

make configuration), a chopper-stabilized instru-

mentation amplifier with fixed gain of 20X,

coarse/fine charge buffers, and a programmable gain

section. For the 25 mV, 55 mV, and 100 mV input

ranges, the input signals are amplified by the 20X in-

strumentation amplifier. For the 1 V, 2.5 V, and 5 V

input ranges, the instrumentation amplifier is by-

passed and the input signals are connected to the

Programmable Gain block via coarse/fine charge

buffers.

VREF+

Differential

4th order

delta-sigma

modulator

Digital

Filter

Programmable

Gain

VREF-

NBV

X20

AIN2+

AIN2-

AIN1+

AIN1-

CS5522

IN+

IN-

AIN4+

AIN4-

AIN1+

AIN1-

CS5524

AIN8+

AIN7+

AIN1+

CS5528

IN+

IN-

IN+

IN-

IN+

IN-

Figure 4. Multiplexer Configurations

NBV also supplies the negative

supply voltage for the coarse/fine

change buffers

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