ISL21080-09 View Datasheet(PDF) - Intersil
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ISL21080-09 Datasheet PDF : 17 Pages
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ISL21080
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 20
is recommended. This network reduces noise
significantly over the full bandwidth. As shown in
Figure 19, noise is reduced to less than 40µVP-P from
1Hz to 1MHz using this network with a 0.01µF capacitor
and a 2kΩ resistor in series with a 10µF capacitor.
400
350
300
CL = 0
CL = 0.001µF
CL = 0.1µF
CL = 0.01µF AND 10µF + 2kΩ
250
200
150
100
50
0
1
10
100
1k
10k
FIGURE 19. NOISE REDUCTION
100k
Turn-On Time
The ISL21080 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. Normal
turn-on time is typically 7ms. This is shown in Figure 18.
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, (VHIGH -
VLOW), and divide by the temperature extremes of
measurement (THIGH – TLOW). 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 specifying temperature coefficient.
VIN = 3.0V
0.1µF
10µF
VIN
VO
ISL21080
GND
0.01µF
2kΩ
10µF
FIGURE 20. NOISE REDUCTION NETWORK
Typical Application Circuits
VIN = 3.0V
R = 200Ω
2N2905
VIN
ISL21080VOUT
GND
2.5V/50mA
0.001µF
FIGURE 21. PRECISION 2.5V 50mA REFERENCE
13
FN6934.2
October 14, 2009
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