X60003 Datasheet, PDF (13/16 Pages) Intersil Corporation – Calibration systems

X60003
Special Applications Considerations
In addition to post-assembly examination, there are also other X-
ray sources that may affect the FGA reference long term
accuracy. Airport screening machines contain X-rays and will
have a cumulative effect on the voltage reference output
accuracy. Carry-on luggage screening uses low level X-rays and is
not a major source of output voltage shift, although if a product
is expected to pass through that type of screening over 100 times
it may need to consider shielding with copper or aluminum.
Checked luggage X-rays are higher intensity and can cause
output voltage shift in much fewer passes, so devices expected to
go through those machines should definitely consider shielding.
Note that just two layers of 1/2 ounce copper planes will reduce
the received dose by over 90%. The leadframe for the device
which is on the bottom also provides similar shielding.
If a device is expected to pass through luggage X-ray machines
numerous times, it is advised to mount a 2-layer (minimum) PC
board on the top, and along with a ground plane underneath will
effectively shield it from 50 to 100 passes through the machine.
Since these machines vary in X-ray dose delivered, it is difficult to
produce an accurate maximum pass recommendation.
Noise Performance and Reduction
The output noise voltage in a 0.1Hz to 10Hz bandwidth is typically
30µV_P-P. This is shown in the plot in the “Typical Performance Curves”
on page 8 and 9. The noise measurement is made with a bandpass
filter made of a 1-pole high-pass filter with a corner frequency at 0.1Hz
and a 2-pole low-pass filter with a corner frequency at 12.6Hz to
create a filter with a 9.9Hz bandwidth. Noise in the 10kHz to 1MHz
bandwidth is approximately 400µV_P-P with no capacitance on the
output, as shown in Figure 34. These noise measurements are made
with a 2 decade bandpass filter made of a 1-pole high-pass filter with
a corner frequency at 1/10 of the center frequency and
1-pole low-pass filter with a corner frequency at 10x the center
frequency. Figure 34 also shows the noise in the 10kHz to 1MHz band
can be reduced to about 50µV_P-P using a 0.001µF capacitor on the
output. Noise in the 1kHz to 100kHz band can be further reduced
using a 0.1µF capacitor on the output, but 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 0.001µF, the
noise reduction network shown in Figure 35 is recommended. This
network reduces noise significantly over the full bandwidth. Figure 35
shows that noise is reduced to less than 40µV_P-P from 1Hz to 1MHz
using this network with a 0.01µF capacitor and a 2k resistor in
series with a 10µF capacitor.
400
350
CL = 0
300
250
200
150
100
50
0
1
CL = 0.001µF
CL = 0.1µF
CL = 0.01µF AND 10µF + 2k
10
100
1k
10k
FIGURE 34. X60003 NOISE REDUCTION
100k
V_IN = 6.5V
0.1µF
10µF
V_IN
X60003^VO
GND
0.01µF
2k
10µF
FIGURE 35. NOISE REDUCTION NETWORK
Turn-On Time
The X60003 device has ultra-low supply current and thus the
time to bias-up internal circuitry to final values will be longer than
with higher power references. Normal turn-on time is typically
7ms. This is shown in the graph, Figure 32. Since devices can
vary in supply current 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 conversions are started.
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 multiplied by 10⁶ to yield
ppm/°C. This is the “Box” method for determining temperature
coefficient.
For additional products, see www.intersil.com/en/products.html
Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted
in the quality certifications found at www.intersil.com/en/support/qualandreliability.html
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time
without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be
accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
Submit Document Feedback 13
FN8137.5
September 1, 2015