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1.4 Device Information
The ADS9227 is a 16-bit, 5-MSPS per channel, dual-channel, simultaneous-sampling, analog-to-digital converter
(ADC). The ADS9227 integrates an ADC driver, precision voltage reference, reference buffer, and common-
mode voltage output buffer. Combined with low conversion latency, high sampling rates, minimal AC and DC
errors, and low temperature drift, the ADS9227 is a high-performance design for applications requiring both
precision and speed.
The serial LVDS (SLVDS) digital interface reduces board layout complexities, relaxes FPGA timing closures,
simplifies firmware, and supports full throughput at lower clock speeds.
2 Hardware
2.1 Analog Interface
This section details the analog input connections to the ADS9227EVM.
2.1.1 ADC Channel Inputs
Each ADC channel in the ADS9227 features an integrated, high-speed ADC driver amplifier. This internal driver
circuit is specifically designed to charge the internal sample-and-hold capacitor in each ADC channel such that
the sampled voltage is fully settled during the minimum acquisition period. In addition, the driver amplifiers
present a high input impedance to the external signal chain. This allows systems engineers to design an analog
input circuit that meets the requirements of the application without also being concerned with performance
degradation due to charge-kickback during sampling.
The ADS9227EVM presents two unique signal chain proposals for the user to evaluate: a high-bandwidth,
fully-differential circuit that supports input frequencies up to 1MHz and a low-bandwidth, high-CMRR circuit with
programmable gain that supports input frequencies up to 300kHz. Either circuit can be used to drive ADC A and
ADC B since the channels are identical by design in the ADS9227.
2.1.1.1 High-bandwidth, Fully-Differential Circuit: THS4551
Figure 2-1
shows the schematic for the THS4551 input circuit connected to ADC A. The THS4551 is a precision,
low-noise, fully differential amplifier with a gain-bandwidth product of 150MHz. This circuit is configured for a
gain of 1V/V and can accept both single-ended and differential inputs. Install R3 and R4 as needed to support
signal sources with 50-Ω output impedance.
The output common-mode voltage on the THS4551 is set by the voltage connected to the VOCM pin. When
used with the ADS9227, TI recommends to buffer the VCMOUT voltage of the ADC before connecting to the
VOCM pin of the THS4551. This makes sure that both amplifier outputs stay within the expected ADC input
common-mode voltage range. The OPA320, shown in
output common-mode voltage on both ADC A and ADC B input circuits.
SBAU439 – JANUARY 2024
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Figure
2-2, is used as the VCMOUT buffer to drive the
Copyright © 2024 Texas Instruments Incorporated
Evaluation Module Overview
ADS9227 Evaluation Module
3
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