X60003 Datasheet, PDF (12/16 Pages) Intersil Corporation – Calibration systems

X60003
Applications Information
FGA Technology
The X60003 voltage references use the floating gate technology to
create references with very low drift and supply current. Essentially
the charge stored on a floating gate cell is set precisely in
manufacturing. The reference voltage output itself is a buffered
version of the floating gate voltage. The resulting reference device
has excellent characteristics which are unique in the industry: very
low temperature drift, high initial accuracy, and almost zero supply
current. Also, the reference voltage itself is not limited by voltage
bandgaps or zener settings, so a wide range of reference voltages
can be programmed (standard voltage settings are provided, but
customer-specific voltages are available).
The process used for these reference devices is a floating gate
CMOS process, and the amplifier circuitry uses CMOS transistors
for amplifier and output transistor circuitry. While providing
excellent accuracy, there are limitations in output noise level and
load regulation due to the MOS device characteristics. These
limitations are addressed with circuit techniques discussed in
other sections.
Handling and Board Mounting
FGA references provide excellent initial accuracy and low
temperature drift at the expense of very little power drain. There
are some precautions to take to insure this accuracy is not
compromised. Excessive heat during solder reflow can cause
excessive initial accuracy drift, so the recommended +260°C
max temperature profile should not be exceeded. Expect up to
1mV drift from the solder reflow process.
FGA references are susceptible to excessive X-radiation like that
used in PC board manufacturing. Initial accuracy can change
10mV or more under extreme radiation. If an assembled board
needs to be X-rayed, care should be taken to shield the FGA
reference device.
Nanopower Operation
Reference devices achieve their highest accuracy when powered
up continuously, and after initial stabilization has taken place.
The X60003 is the first high precision voltage reference with ultra
low power consumption that makes it practical to leave power-on
continuously in battery operated circuits. The X60003 consume
extremely low supply current due to the proprietary FGA
technology. Supply current at room temperature is typically
500nA which is 1 to 2 orders of magnitude lower than
competitive devices. Application circuits using battery power will
benefit greatly from having an accurate, stable reference which
essentially presents no load to the battery.
In particular, battery-powered data converter circuits that would
normally require the entire circuit to be disabled when not in use
can remain powered-up between conversions as shown in Figure
33. Data acquisition circuits providing 12 to 24-bits of accuracy
can operate with the reference device continuously biased with
no power penalty, providing the highest accuracy and lowest
possible long term drift.
Other reference devices consuming higher supply currents will
need to be disabled in between conversions to conserve battery
capacity. Absolute accuracy will suffer as the device is biased
and requires time to settle to its final value, or, may not actually
settle to a final value as power-on time may be short.
V_IN = +6V TO 9V
10µF
0.01µF
V_{IN VOUT}
X60003
GND
0.001µF
SERIAL
BUS
REF IN
ENABLE
SCK
SDAT
12 TO 24-bit
A/D CONVERTER
FIGURE 33. BATTERY-POWERED DATA CONVERTER CIRCUITS
Board Mounting Considerations
For applications requiring the highest accuracy, board mounting
location should be reviewed. Placing the device in areas subject
to slight twisting can cause degradation of the accuracy of the
reference voltage due to die stresses. It is normally best to place
the device near the edge of a board, or the shortest side, as the
axis of bending is most limited at that location. Obviously
mounting the device on flexprint or extremely thin PC material
will likewise cause loss of reference accuracy.
Board Assembly Considerations
FGA references provide high accuracy and low temperature drift
but some PC board assembly precautions are necessary. Normal
Output voltage shifts of 100µV to 1mV can be expected with
Pb-free reflow profiles or wave solder on multi-layer FR4 PC
boards. Precautions should be taken to avoid excessive heat or
extended exposure to high reflow or wave solder temperatures,
this may reduce device initial accuracy.
Post-assembly x-ray inspection may also lead to permanent
changes in device output voltage and should be minimized or
avoided. If x-ray inspection is required, it is advisable to monitor
the reference output voltage to verify excessive shift has not
occurred. If large amounts of shift are observed, it is best to add
an X-ray shield consisting of thin zinc (300µm) sheeting to allow
clear imaging, yet block x-ray energy that affects the FGA
reference.
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FN8137.5
September 1, 2015