8

FN8140.0

March 15, 2005

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 2k

Ω resistor in series with a 10µF

capacitor.

Figure 2.

Figure 3.

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.

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

the nominal reference voltage (at T = 25°C) and multi-

CL = 0

CL = .001µF

CL = .1µF

CL = .01µF & 10µF + 2k

Ω

400

350

300

250

200

150

100

50

0

1

10

100

1000

10000

100000

X60008-25 NOISE REDUCTION

GND

X60008-25

.01µF

10µF

2k

Ω

.1µF

10µF

0

1

2

3

4

5

6

-1

1

3

5

7

9

690 nA

520 nA

320 nA

X60008 TURN-ON TIME (25

°C)

TIME (mSec)

X60008B-25