LTC2751-14 Linear Technology Corporation, LTC2751-14 Datasheet - Page 16

• Manufacturer Part Number: LTC2751-14
• Description: Ltc2751-14 - Current Output 14-bit Softspan Dacs With Parallel I/o
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LTC2751
Op Amp Selection
Because of the extremely high accuracy of the 16-bit
LTC2751-16, careful thought should be given to op amp
selection in order to achieve the exceptional performance
of which the part is capable. Fortunately, the sensitivity of
INL and DNL to op amp offset has been greatly reduced
compared to previous generations of multiplying DACs.
Tables 3 and 4 contain equations for evaluating the effects
of op amp parameters on the LTC2751’s accuracy when
Table 5. Partial List of LTC Precision Amplifi ers Recommended for Use with the LTC2751 with Relevant Specifi cations
AMPLIFIER
LT1001
LT1097
LT1112 (Dual)
LT1124 (Dual)
LT1468
LT1469 (Dual)
16
Table 3. Variables for Each Output Range That Adjust the
Equations in Table 4
Table 4. Easy-to-Use Equations Determine Op Amp Effects on DAC Accuracy in All Output Ranges (Circuit of Page 1). Subscript 1
Refers to Output Amp, Subscript 2 Refers to Reference Inverting Amp.
A
A
V
V
VOL1
VOL2
I
OP AMP
OS1
I
OS2
B2
B1
OUTPUT RANGE
–2.5V to 7.5V
(mV)
(nA)
(mV)
(mV)
(V/V)
(V/V)
±2.5V
±10V
10V
±5V
5V
I
B1
V
OS1
• 0.0003 •
A1 •
INL (LSB)
• 3.2 •
(
0
0
0
A
V
125
16.5k
µV
25
50
60
70
75
VOL1
OS
1.1
2.2
1.9
( )
A1
( )
V
2
4
1
V
5V
REF
5V
REF
)
I
V
B1
0.35
0.25
A2
nA
20
10
10
OS1
I
2
3
2
4
1
3
2
B
• 0.00008 •
DNL (LSB)
A2 •
• 0.82 •
(
0
0
0
A
0.83
0.5
1.4
0.7
1.5k
A3
VOL1
1
1
V/mV
A
1000
1500
4000
5000
2000
( )
800
V
( )
VOL
V
5V
REF
5V
)
REF
0.5
A4
A3 • V
1
1
1
VOLTAGE
nV/√ ⎯ H ⎯ z
I
NOISE
B1
OFFSET (LSB)
2.7
10
14
14
OS1
5
5
UNIPOLAR
• 0.13 •
1.5
1.5
2.5
1.5
A5
1
1
• 13.2 •
0
0
0
0
AMPLIFIER SPECIFICATIONS
CURRENT
( )
V
pA/√ ⎯ H ⎯ z
NOISE
5V
0.008
0.008
REF
0.12
( )
0.3
0.6
0.6
V
5V
REF
programmed in a unipolar or bipolar output range. These
are the changes the op amp can cause to the INL, DNL,
unipolar offset, unipolar gain error, bipolar zero and bipolar
gain error. Tables 3 and 4 can also be used to determine
the effects of op amp parameters on the LTC2751-14
and the LTC2751-12. However, the results obtained from
Tables 3 and 4 are in 16-bit LSBs. Divide these results
by 4 (LTC2751-14) and 16 (LTC2751-12) to obtain the
correct LSB sizing.
Table 5 contains a partial list of LTC precision op amps
recommended for use with the LTC2751. The easy-to-use
design equations simplify the selection of op amps to meet
the system’s specifi ed error budget. Select the amplifi er
from Table 5 and insert the specifi ed op amp parameters
in Table 4. Add up all the errors for each category to de-
termine the effect the op amp has on the accuracy of the
part. Arithmetic summation gives an (unlikely) worst-case
effect. A root-sum-square (RMS) summation produces a
more realistic estimate.
A4 • V
A3 • V
A4 • I
I
B1
SLEW
(
RATE
V/µs
0.25
0.16
(
BIPOLAR ZERO
0.2
4.5
ERROR (LSB)
22
22
OS1
OS2
B2
A4 •
• 0.13 •
• 0.13 •
• 19.8 •
• 13.1 •
0
(
A
66k
VOL2
( )
V
GAIN BANDWIDTH
5V
REF
( )
V
( )
( )
)
V
V
5V
REF
PRODUCT
5V
5V
REF
REF
MHz
0.75
12.5
0.8
0.7
90
90
)
)
I
V
V
B1
OS1
I
UNIPOLAR GAIN
OS2
B2
ERROR (LSB)
• 0.0018 •
A5 •
• 0.26 •
• 13.2 •
• 26.2 •
(
A
131k
VOL2
(
A
with LTC2751
131k
VOL1
( )
t
( )
V
)
( )
( )
SETTLING
V
V
V
5V
REF
5V
REF
5V
5V
120
120
115
REF
REF
19
µs
)
2
2
V
I
V
B1
I
OS1
OS2
B2
BIPOLAR GAIN
ERROR (LSB)
• 0.0018 •
A5 •
• 0.26 •
• 13.2 •
DISSIPATION
(
10.5/Op Amp
• 26.2 •
123/Op Amp
A
69/Op Amp
131k
VOL2
POWER
(
A
mW
117
131k
46
11
VOL1
( )
)
( )
( )
V
V
( )
V
5V
REF
5V
V
REF
5V
REF
5V
2751f
REF
)