Texas Instruments ADS9224REVM-PDK, User Manual, Page: 5 / 34

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Analog Interface
5 SBAU315A – July 2018 – Revised June 2019
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ADS9224REVM-PDK
2 Analog Interface
The ADS9224R is a dual-channel, simultaneous-sampling ADC that supports fully-differential inputs. Each
channel of the ADS9224R uses a
THS4551 fully-differential amplifier (FDA) to drive the differential inputs
of the ADC. This section covers driver details and board connections for a differential signal source.
2.1 Connectors for Signal Source
The ADS9224REVM is designed for easy interfacing to multiple analog sources. SMA connectors allow
the EVM to have input signals connected through coaxial cables. In addition, header connectors JP1
through JP4 provide a convenient way to connect input signals. All analog inputs are buffered by the
THS4551 high-speed FDA in order to properly drive the ADS9224R ADC inputs.
Table 1. J2 to J5 SMA Analog Interface Connections
Pin Number Signal Description
J2 AIN-_A
CHA negative differential input. This SMA connector can be grounded by
installing a shunt on JP1 for single-ended signals.
1-k
Ω
input impedance
J3 AIN+_A
CHA positive differential input or input for single-ended signals.
1-k
Ω input impedance
J4 AIN+_B
CHB positive differential input or input for single-ended signals.
1-k
Ω input impedance
J5 AIN-_B
CHB negative differential input. This SMA connector can be grounded by
installing a shunt on JP4 for single-ended signals.
1-k
Ω input impedance
Table 2. JP1 to JP4 Header Descriptions
Pin Number Signal Description
JP1.1 AIN-_A
CHA negative differential input. This SMA connector can be grounded by
installing a shunt on JP1 for single-ended signals.
1-k
Ω input impedance.
JP2.1 AIN+_A
CHA positive differential input or input for single-ended signals.
1-k
Ω input impedance.
JP3.1 AIN+_B
CHB positive differential input or input for single-ended signals.
1-k
Ω
input impedance.
JP4.1 AIN-_B
CHB negative differential input. This SMA connector can be grounded by
installing a shunt on JP4 for single-ended signals.
1-k
Ω input impedance.
2.2 ADC Differential Input Signal Driver
The analog inputs of the ADS9224R SAR ADC are not high-impedance but rather present a dynamic load
as the sample-and-hold switches open and close. The current demand of the SAR ADC input increases as
a function of the sampling rate. Thus, the evaluation board provides the THS4551 FDA driver that
maintains ADC performance with maximum loading at the full device throughput of 3 MSPS.