HMC661LC4B Datasheet, PDF (6/14 Pages) Hittite Microwave Corporation – ULTRA-WIDEBAND 4 GS/s TRACK-AND-HOLD AMPLIFIER

HMC661LC4B
v00.0312
ULTRA-WIDEBAND 4 GS/s TRACK-AND-HOLD AMPLIFIER
DC - 18 GHz
Definition of Specifications
Aperture Delay: The delay of the exact sample time relative to the time that the hold command is applied to the
device. It is the difference between the delay of the clock switching transition to the hold node and the input signal
group delay to the hold node. If the input signal group delay to the hold node exceeds the clock delay this quantity
can be negative.
Aperture Jitter: The standard deviation of the sample instant in time.
Acquisition Time: The interval between the internal hold-to-track transition and the time at which the hold-node
signal is tracking the input signal within a specified accuracy. It does not include the pipeline delay of the clock
buffer.
Differential Pedestal: A component in the sample value caused by charge redistribution in the T/H switch during the
sampling transition. In general, the pedestal can consist of three components: a fixed offset, a component that is
linearly related to input signal amplitude, and a component that is nonlinearly related to input signal amplitude.
The majority of the pedestal is usually linear. The value of the pedestal can be approximated by
P = P_o + P_lin V_in
where, P_o is the fixed pedestal component, P_lin is the linear pedestal component, and V_in is the sampled signal
level.
Differential Droop Rate: The slow drift in the differential output voltage of a held sample while the T/H is in hold-mode.
It is typically caused by current leakage on the hold capacitors and corresponds to a decay in the held voltage
with increasing time. The droop can be approximated as the sum of a fixed component and a component that is
linearly related to the held sample voltage. The total droop can be approximated by D = D_o + D_lin Vin where D_o is
the fixed component, D_lin is the linear droop constant and V_in is the sampled signal level. The sign of D_o tends to
be random so only the magnitude is specified. Since the droop is mostly linear, it causes little nonlinearity.
Feedthrough Rejection: A measure of the off-state (hold-mode) isolation of the T/H’s internal switch. It is defined as
the ratio of the amplitude of the output signal (for a sinusoidal input) feeding through during the hold mode to the
amplitude of the output signal during track mode. Normalization by the track-mode signal gives the true switch
isolation without the effects of the output amplifier bandwidth limiting.
Full Scale Range: The voltage range between the minimum and maximum signal levels that can be handled by the
T/H while still meeting the specifications.
Sampling Bandwidth: The -3 dB bandwidth of the sampled signal levels represented by the held sample amplitudes.
It includes both the bandwidth of the transfer function from the signal input to the hold-node and any band-limiting
effects associated with the finite time duration of the sampling aperture.
Settling Time: The interval between the internal track-hold transition and the time at which the held output signal is
settled to within a specified accuracy. It does not include the pipeline delay of the clock buffer but does include
the group delay of the output amplifier.
Spurious Free Dynamic Range (SFDR): The ratio (usually expressed in dB) between the sinusoidal output signal
amplitude and the amplitude of the largest non-linearity product falling within one Nyquist bandwidth. It may be
specified for both full scale input and some fraction(s) of full scale input. A SFDR based only on 2^nd order nonlinear
products is referred to as the 2^nd order SFDR (SFDR2). A SFDR based only on 3^rd order products is referred to as
the 3^rd order SFDR (SFDR3).
Total Harmonic Distortion (THD): The ratio of the total power in the non-linearity-generated harmonics and harmonic
aliases (measured in one Nyquist band) to the output signal power.
For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824
Phone: [phone] Fax: [phone] Order On-line at www.hittite.com
6
Application Support: Phone: [phone] or [e-mail]