THS4552 Datasheet, PDF (61/71 Pages) Texas Instruments – Dual-Channel, Low-Noise, Precision, 150-MHz, Fully Differential Amplifier

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13 Device and Documentation Support
THS4552
SBOS831 – DECEMBER 2016
13.1 Device Support
13.1.1 TINA-TI™ Simulation Model Features
The device model is available on the product folder under www.ti.com in a typical application circuit file. The
model includes numerous features intended to speed designer progress over a wide range of application
requirements. The following list shows the performance parameters included in the model:
• For the small-signal response shape with any external circuit:
– Differential open-loop gain and phase
– Parasitic input capacitance
– Open-loop differential output impedance
• For noise simulations:
– Input differential spot voltage noise and a 100-Hz 1/f corner
– Input current noise on each input with a 6-kHz 1/f corner
• For time-domain, step-response simulations:
– Differential slew rate
– I/O headroom models to predict clipping
– Input stage diodes to predict overdrive limiting
• Fine-scale, dc precision terms:
– PSRR
– CMRR
The Typical Characteristics: 3-V to 5-V Supply Range section provides more detail than the macromodels can
provide; some of the unmodeled features include:
• Harmonic distortion
• Temperature drift in dc error terms (V_IO and I_OS)
• Overdrive recovery time
• Turn-on and turn-off times using the power-down feature
Some unique simulation considerations come with the THS4552 TINA-TI™ model. This device (and model)
include 0.6-pF internal feedback capacitors. These capacitors are intended to improve phase margin when using
higher external feedback resistor values. Higher feedback resistors generate an in-band pole in the feedback
signal with the differential input capacitance, and the internal 0.6 pF capacitors add a zero to the feedback
response shape to shape the noise gain flat at the loop-gain crossover.
In order to generate an accurate open-loop gain and phase simulation, these components must be removed
because they are feedback elements, not forward path elements. Figure 102 illustrates a typical A_OL gain and
phase simulation (available as a TINA-TI™ software file) where external –0.6-pF capacitors cancel out the
internal capacitors in the model (TINA-TI™ supports negative value elements). The inductors inside the loop
close the loop for the dc operating point and open the loop immediately for an ac sweep. The input-coupling
capacitors are open at dc, then couple in the differential input immediately on an ac sweep. The somewhat odd
values help reduce numerical chatter in the simulation. When using the internal feedback traces from the outputs
to the inputs on the RTW package, be sure to add the 3.3-Ω trace impedance to any simulation. This impedance
is not included in the core model.
Copyright © 2016, Texas Instruments Incorporated
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