LTC1657L Linear Technology Corporation, LTC1657L Datasheet - Page 13

• Manufacturer Part Number: LTC1657L
• Description: Ltc1657l - Parallel 16-bit Rail-to-rail Micropower Dac
• Manufacturer: Linear Technology Corporation

This circuit shows a digitally programmable current source
from an external voltage source using an external op amp,
an LT1218 and an NPN transistor (2N3440). Any digital
word from 0 to 65535 is loaded into the LTC1657 and its
output correspondingly swings from 0V to 4.096V. This
voltage will be forced across the resistor R
TYPICAL APPLICATIO S
P
5:19
28
27
2
3
1
DATA (0:15)
CSLSB
CSMSB
WR
LDAC
CLR
U
X1/X2
26
REFHI
REFLO
Digitally Programmable Current Source
LTC1657
22
21
REFOUT
A
GND
. If R
20
23
V
5V
CC
A
is
V
OUT
25
chosen to be 412 , the output current will range from
0mA at zero scale to 10mA at full scale. The minimum
voltage for V
Q1’s V
voltage source can be 5V.
0.1 F
3
2
–
+
CESAT
LT1218
7
4
S
voltage. With a load resistor of 50 , the
is determined by the load resistor R
5V < V
FOR R
6
S
L
< 100V
Q1
2N3440
R
412
1%
R
LTC1657/LTC1657L
50
A
L
I
OUT
1657 TA04
=
(D
(65536)(R
0mA TO 10mA
IN
)(4.096)
A
)
13
L
and