ISL21080 Datasheet, PDF (8/10 Pages) Intersil Corporation – 300nA NanoPower Voltage References

ISL21080
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 20 is recommended. This network reduces
noise significantly over the full bandwidth. As shown in
Figure 19, noise is reduced to less than 40µV_P-P from 1Hz
to 1MHz using this network with a 0.01µF capacitor and a
2kΩ resistor in series with a 10µF capacitor.
400
CL = 0
350
CL = 0.001µF
CL = 0.1µF
300
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, (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
specifying temperature coefficient.
V_IN = 3.0V
0.1µF
10µF
V_IN
V_O
ISL21080
GND
0.01µF
2kΩ
10µF
FIGURE 20. NOISE REDUCTION NETWORK
Typical Application Circuits
V_IN = 3.0V
R = 200Ω
2N2905
V_IN
ISL21080 ^VOUT
GND
2.5V/50mA
0.001µF
FIGURE 21. PRECISION 2.5V 50mA REFERENCE
8
FN6934.0
July 28, 2009