CS5525-ASZ datasheet(8/30 Pages) CIRRUS

8 / 30 page

CS5525 CS5526

DS202F5

DETAILED DESCRIPTION

The CS5525 and CS5526 are 16-bit and 20-bit pin

compatible converters which include a chopper-

stabilized instrumentation amplifier input, and an

on-chip programmable gain amplifier. They are

both optimized for measuring low-level unipolar or

bipolar signals in process control and medical ap-

plications.

The CS5525/26 also include a fourth order delta-

sigma modulator, a calibration microcontroller,

eight digital filters, a 4-bit analog latch, and a serial

port.

The digital filters provide any one of eight

different output update rates.

The CS5525/26 include a CPD (Charge Pump

Drive) output (shown in Figure 1). CPD provides a

negative bias voltage to the on-chip instrumenta-

tion amplifier when used with a combination of ex-

ternal diodes and capacitors. This enables the

CS5525/26 to measure negative voltages with re-

spect to ground, making the converters ideal for

thermocouple temperature measurements.

Theory of Operation

The CS5525/26 A/D converters are designed to op-

erate from a single +5 V analog supply and provide

several different input ranges. See the Analog

Characteristics section on page 3 for details.

Figure 1 illustrates the CS5525/26 connected to

generate their own negative bias supply using the

on-chip CPD (Charge Pump Drive). This enables

the CS5525/26 to measure ground referenced sig-

nals with magnitudes down to NBV (Negative Bias

Voltage, approximately -2.1 V in this example).

Figure 2 illustrates a charge pump circuit when the

converters are powered from a +3.0 V digital sup-

ply. Alternatively, the negative bias supply can be

generated from a negative supply voltage or a resis-

tive divider as illustrated in Figure 3.

Figure 1. CS5525/26 Configured to use on-chip charge pump to supply NBV.

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