THP210 datasheet(18/41 Pages) TI

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8.3.5 Unity Gain Stability

The stability of the amplifiers is of key importance when designing application circuits with fully differential

amplifiers. This stability becomes especially important when driving capacitive loads, such as the input for

successive-approximation-register (SAR) analog-to-digital converters (ADCs). A trade-off is made between the

bandwidth of an amplifier and keeping power consumption low; in many cases, FDAs are not unity gain stable.

Currently, many FDAs are primarily designed to support high-speed ADCs, and thus, are typically

decompensated. This decompensation comes with the drawback that the noise performance degrades because

of noise gain peaking. Additional components and compensation techniques are required to handle these

challenges and prevent potential instability of the FDA. For detailed analysis of how stability is defined and

affected, see TI Precision Labs – Fully Differential Amplifiers – FDA Stability and Simulating Phase Margin.

The THP210 is unity-gain stable; therefore, this device can be used in gain configurations with gains > 1, and

also in attenuating configurations with gains < 1, without requiring compensation techniques and sacrificing

dynamic performance. This device can be of prime use for applications that need to interface large input signals

to the low-voltage ADC domain.

8.4 Device Functional Modes

The THP210 has two functional modes: normal operation and power-down. The power-down state is enabled

when the voltage on the power-down pin is lowered to less than the power-down threshold. In the power-down

state, the quiescent current is significantly reduced, and the output voltage is high-impedance. This high

impedance can lead to the input voltages (VIN+ and VIN–) separating.

Internal ESD protection diodes remain present across the input pins in both operating and power-down mode.

Large input signals during disable can forward-biasing the ESD protection diodes, thus producing a load current

in the supply, even in power-down. See Section 9.1.5 for guidance on power-down operation.

The VOCM control pin sets the output average voltage. If left open, VOCM defaults to an internal midsupply

value. Driving this high-impedance input with a voltage reference within the valid range sets a target for the

internal VCM error amplifier. If floated to obtain a default midsupply reference for VOCM, an external decoupling

capacitor must be added on the VOCM pin to reduce the otherwise high output noise for the internal high-

impedance bias.

THP210

SBOS932B – FEBRUARY 2020 – REVISED OCTOBER 2020

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THP210 Datasheet(PDF) 18 Page - Texas Instruments