AD7761BSTZ datasheet(5/76 Pages) AD

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AD7761

Data Sheet

Rev. A | Page 4 of 75

GENERAL DESCRIPTION

The AD7761 is an 8-channel, simultaneous sampling sigma-delta

(Σ-Δ) analog-to-digital converter (ADC) with a Σ-Δ modulator

and digital filter per channel, enabling synchronized sampling of ac

and dc signals.

The AD7761 achieves 97.7 dB dynamic range at a maximum

input bandwidth of 110.8 kHz, combined with typical performance

of ±1 LSB integral nonlinearity (INL), ±1 LSB offset error, and

±5 LSB gain error.

The AD7761 user can trade off input bandwidth, output data rate,

and power dissipation. Select one of three power modes to optimize

the device for noise targets and power consumption. The

flexibility of the AD7761 allows it to become a reusable platform

for low power dc and high performance ac measurement

modules.

The AD7761 has three modes: fast mode (256 kSPS maximum,

110.8 kHz input bandwidth, 51.5 mW per channel), median

mode (128 kSPS maximum, 55.4 kHz input bandwidth, 27.5 mW

per channel) and low power mode (32 kSPS maximum, 13.8 kHz

input bandwidth, 9.375 mW per channel).

The AD7761 offers extensive digital filtering capabilities, such as

a wideband, low ±0.005 dB pass-band ripple, antialiasing low-

pass filter with sharp roll-off, and 105 dB attenuation at the

Nyquist frequency.

Frequency domain measurements can use the wideband linear

phase filter. This filter has a flat pass band (±0.005 dB ripple)

from dc to 102.4 kHz at 256 kSPS, from dc to 51.2 kHz at

128 kSPS, or from dc to 12.8 kHz at 32 kSPS.

The AD7761 also offers sinc response via a sinc5 filter, a low

latency path for low bandwidth, and low noise measurements.

The wideband and sinc5 filters can be selected and run on a per

channel basis.

Within these filter options, the user can improve the dynamic

range by selecting from decimation rates of ×32, ×64, ×128,

×256, ×512, and ×1024. The ability to vary the decimation

filtering optimizes noise performance to the required input

bandwidth.

Embedded analog functionality on each ADC channel makes

design easier, such as a precharge buffer on each analog input

that reduces analog input current and a precharge reference

buffer per channel reduces input current and glitches on the

reference input terminals.

The device operates with a 5 V AVDD1A and AVDD1B supply,

a 2.25 V to 5.0 V AVDD2A and AVDD2B supply, and a 2.5 V to

3.3 V or 1.8 V IOVDD supply (see the 1.8 V IOVDD Operation

section for specific requirements for operating at 1.8 V IOVDD).

The device requires an external reference; the absolute input

reference voltage range is 1 V to AVDD1 − AVSS.

For the purposes of clarity within this data sheet, the AVDD1A

and AVDD1B supplies are referred to as AVDD1 and the AVDD2A

and AVDD2B supplies are referred to as AVDD2. For the

negative supplies, AVSS refers to the AVSS1A, AVSS1B,

AVSS2A, AVSS2B, and AVSS pins.

The specified operating temperature range is −40°C to +105°C.

The device is housed in a 10 mm × 10 mm 64-lead LQFP package

with a 12 mm × 12 mm printed circuit board (PCB) footprint.

Throughout this data sheet, multifunction pins, such as

XTAL2/MCLK, are referred to either by the entire pin name or

by a single function of the pin, for example MCLK, when only

that function is relevant.

AD7761BSTZ Datasheet(PDF) 5 Page - Analog Devices

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