LT6657
elecTrical characTerisTics
Note 5: Line and load regulation are measured on a pulse basis for
specified input voltage or load current ranges. Output voltage change due
to die temperature change must be taken into account separately.
Note 7: Long term stability typically has a logarithmic characteristic
and therefore change after 1000 hours tend to be much smaller than
before that time. Total drift in the second thousand hours is normally
less than one third of the first thousand hours with a continuing trend
toward reduced drift with time. Long-term stability will also be affected by
differential stresses between the IC and the board material created during
board assembly.
Note 8 : Hysteresis in output voltage is created by mechanical stress that
depends on whether the IC was previously at a different temperature.
Output voltage is always measured at 25°C, but the IC is cycled 25°C to
cold to 25°C, or 25°C to hot to 25°C before successive measurements.
Hysteresis measures the maximum output change for the averages of
three hot or cold temperature cycles, preconditioned by one cold and one
hot cycles. For instruments that are stored at well controlled temperatures
(within 30 degrees of the operational temperature), hysteresis is usually
not a significant error source.
Note 6: Peak-to-peak noise is measured with a 2-pole highpass filter at
0.1Hz and 3-pole lowpass filter at 10Hz. The unit is enclosed in a still-air
environment to eliminate thermocouple effects on the leads, and the
test time is 10 seconds. Due to the statistical nature of noise, repeating
noise measurements will yield larger and smaller peak values in a given
measurement interval. By repeating the measurement for 1000 intervals,
each 10 seconds long, it is shown that there are time intervals during
which the noise is higher than in a typical single interval, as predicted by
statistical theory. In general, typical values are considered to be those for
which at least 50% of the units may be expected to perform similarly or
better. For the 1000 interval test, a typical unit will exhibit noise that is
less than the typical value listed in the Electrical Characteristics table in
more than 50% of its measurement intervals. See ꢀpplication Note 124 for
noise testing details. RMS noise is measured with a spectrum analyzer in a
shielded environment.
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