LTC1451_15 Datasheet, PDF (10/12 Pages) Linear Technology – 12-Bit Rail-to-Rail Micropower DACs in SO-8

LTC1451
LTC1452/LTC1453
TYPICAL APPLICATIO S
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_IN
V_CC
CLK
µP
LTC145X VOUT
CS/LD
D_OUT V_REF GND
TO NEXT DAC FOR
DAISY-CHAINING
LTC1451: 2.048V
LTC1452: EXTERNAL
LTC1453: 1.22V
0.1µF
OUTPUT
LTC1451: 0V TO 4.095V
LTC1452: 0V TO 2 • REF
LTC1453: 0V TO 2.5V
1451/2/3 TA03
Digitally Programmable Current Source
5V
0.1µF
V_S + 5V TO 100V
FOR R_L ≤ 50Ω
V_CC
CLK
R_L
I_OUT
=
D_IN • 4.095
4096 • R_A
≈
0mA
TO
10mA
µP
D_IN LTC1451 ^VOUT
+
CS/LD
GND
LT1077
–
Q1
2N3440
R_A
410Ω
1451/2/3 TA05
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
resistor R_A. If R_A is chosen to be 410Ω the output current
will range from 0mA at zero-scale to 10mA at full-scale.
The minimum voltage for V_S is determined by the load
resistor R_L and Q1's V_CESAT voltage. With a load resistor
of 50Ω, the voltage source can be as low as 5V.
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