Rainbow Electronics ADC0838 - Manual (Page 16)

Functional Description
(Continued)
This zener is intended for use as a shunt voltage regulator
to eliminate the need for any additional regulating compo-
nents This is most desirable if the converter is to be re-
motely located from the system power source
Figures 4
and 5 illustrate two useful applications of this on-board ze-
ner when an external transistor can be afforded
An important use of the interconnecting diode between V a
and V CC is shown in Figures 6 and 7 Here this diode is
used as a rectifier to allow the V
CC
supply for the converter
to be derived from the clock The low current requirements
of the A D and the relatively high clock frequencies used
(typically in the range of 10k – 400 kHz) allows using the
small value filter capacitor shown to keep the ripple on the
V
CC
line to well under of an LSB The shunt zener regula-
tor can also be used in this mode This requires a clock
voltage swing which is in excess of V
Z A current limit for the
zener is needed either built into the clock generator or a
resistor can be used from the CLK pin to the V
a pin
Applications
TL H 5583 – 12
FIGURE 4 Operating with a Temperature
Compensated Reference
TL H 5583 – 34
FIGURE 5 Using the A D as
the System Supply Regulator
TL H 5583 – 35
FIGURE 6 Generating V CC from the Converter Clock
TL H 5583 – 36
FIGURE 7 Remote Sensing
Clock and Power on 1 Wire
Note 4 5V s V CC s 6 3V
16