Pentek 6210 Operating Manual page 162

LTC1451
LTC1452/LTC1453
TYPICAL APPLICATIO S
µP
This circuit shows a digitally programmable current source
from an external voltage source using an external op amp,
an LT1077 and an NPN transistor (2N3440). Any digital
word from 0 to 4095 is loaded into the LTC1451 and its
output correspondingly swings from 0V to 4.095V. In the
configuration shown, this voltage will be forced across the
10
12-Bit 3V to 5V Voltage Output DAC
LTC1451: 4.5V TO 5.5V
LTC1452: 2.7V TO 5.5V
LTC1453: 2.7V TO 5.5V
D V
CC
IN
CLK
µP
LTC145X
CS/LD
D V
OUT REF
TO NEXT DAC FOR
LTC1451: 2.048V
DAISY-CHAINING
LTC1452: EXTERNAL
LTC1453: 1.22V
Digitally Programmable Current Source
5V
0.1µF
V
CC
CLK
V
LTC1451
D
OUT
IN
CS/LD
GND
0.1µF
V
OUTPUT
OUT
LTC1451: 0V TO 4.095V
LTC1452: 0V TO 2 • REF
GND
LTC1453: 0V TO 2.5V
1451/2/3 TA03
V + 5V TO 100V
S
≤ 50Ω
FOR R
L
R I
L OUT
+
Q1
LT1077
2N3440
–
R
A
410Ω
1451/2/3 TA05
resistor R . If R is chosen to be 410Ω the output current
A A
will range from 0mA at zero-scale to 10mA at full-scale.
The minimum voltage for V
resistor R and Q1's V
L
of 50Ω, the voltage source can be as low as 5V.
D • 4.095
IN
≈ 0mA TO 10mA
=
4096 • R
A
is determined by the load
S
voltage. With a load resistor
CESAT