X60008E-50 Datasheet, PDF (10/14 Pages) Intersil Corporation – Precision 5.0V FGA Voltage Reference

X60008E-50
noise in the 1Hz to 100Hz band increases due to
instability of the very low power amplifier with a 0.1µF
capacitance load. For load capacitances above
.001µF the noise reduction network shown in fig. 3 is
recommended. This network reduces noise sig-
nificantly over the full bandwidth. As shown in fig. 2,
noise is reduced to less than 40µVp-p from 1Hz to
1MHz using this network with a .01µF capacitor and a
2kΩ resistor in series with a 10µF capacitor.
Figure 2.
400
350
300
250
200
150
100
50
0
1
X60008-50 NOISE REDUCTION
CL = 0
CL = .001µF
CL = .1µF
CL = .01µF & 10µF + 2kΩ
10
100
1000 10000 100000
Figure 3.
V_IN = 6.5V
.1µF
10µF
V_IN
V_O
X60008-50
GND
.01µF
2kΩ
10µF
Turn-On Time
The X60008 devices have ultra-low supply current and
thus the time to bias up internal circuitry to final values
will be longer than with higher power references. Nor-
mal turn-on time is typically 7ms. This is shown in the
graph, Figure 4. Since devices can vary in supply cur-
rent down to 300nA, turn-on time can last up to about
12ms. Care should be taken in system design to
include this delay before measurements or conver-
sions are started.
Figure 4.
X60008-50 TURN-ON TIME (25°C)
7
6
5
4
I_IN = 730nA
I_IN = 500nA
3
I_IN = 320nA
2
1
0
-1 1 3 5 7 9 11 13 15
TIME (mSec)
Temperature Coefficient
The limits stated for temperature coefficient (tempco)
are governed by the method of measurement. The
overwhelming standard for specifying the temperature
drift of a reference is to measure the reference voltage
at two temperatures, take the total variation, (V_HIGH -
V_LOW), and divide by the temperature extremes of
measurement (T_HIGH - T_LOW). The result is divided by
the nominal reference voltage (at T = 25°C) and multi-
plied by 10⁶ to yield ppm/°C. This is the “Box” method
for temperature coefficient which allows comparison of
devices but can mislead a designer concerned about
specific ranges of temperature (i.e., 35°C to 65°C for a
power supply design). The designer may infer the
tempco to be a well-behaved flat line slope, similar to
that shown in Figure 5. The slope of the Vout vs. tem-
perature curve at points in-between the extremes can
actually be much higher than the tempco stated in the
specifications due to multiple inflections in the temper-
ature drift curve. Most notably, bandgap devices may
have some type of “s-curve” which will have slopes
that exceed the average specified tempco by 2x or 3x.
10
FN8145.0
March 14, 2005