ltc2752lx Linear Technology Corporation, ltc2752lx Datasheet - Page 20

• Manufacturer Part Number: ltc2752lx
• Description: Ltc2752 Dual16-bit Softspan Iout Dacs Features
• Manufacturer: Linear Technology Corporation

LTC2752
Op Amp Selection
Because of the extremely high accuracy of the 16-bit
LTC2752, 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 4 and 5 contain equations for evaluating the ef-
fects of op amp parameters on the LTC2752’s accuracy
when 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.
Table 6 contains a partial list of Linear Technology preci-
sion op amps recommended for use with the LTC2752.
The easy-to-use design equations simplify the selection
A
A
applicaTions inForMaTion
Table 5. 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.
Table 6. Partial List of LTC Precision Amplifiers Recommended for Use with the LTC2752 with Relevant Specifications
AMPLIFIER
LT1001
LT1097
LT1112 (Dual)
LT1124 (Dual)
LT1468
LT1469 (Dual)
0
VOL1
VOL2
V
V
OP AMP
OS1
I
OS2
I
B1
B2
(nA)
(nA)
(V/mV)
(V/mV)
(mV)
(mV)
I
B1
V
OS1
• 0.0003 •
A1 •
INL (LSB)
• 3 •
V
125
0
0
0
A
µV
25
50
60
70
75
16.5
OS
VOL1
V
5V
REF
V
5V
REF
I
V
B1
0.35
0.25
nA
20
10
10
I
OS1
2
B
• 0.00008 •
DNL (LSB)
A2 •
• 0.78 •
0
0
0
A
VOL1
1.5
V/mV
A
1000
1500
4000
5000
2000
800
V
VOL
V
5V
REF
5V
REF
A3 • V
VOLTAGE
nV/√Hz
I
NOISE
OFFSET (LSB)
B1
2.7
10
14
14
UNIPOLAR
5
5
OS1
• 0.13 •
• 13.1 •
0
0
0
0
AMPLIFIER SPECIFICATIONS
CURRENT
V
pA/√Hz
NOISE
0.008
0.008
5V
REF
0.12
0.3
0.6
0.6
V
5V
REF
of op amps to meet the system’s specified error budget.
Select the amplifier from Table 6 and insert the specified
op amp parameters in Table 5. Add up all the errors for
each category to determine 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.
Table 4. Coefficients for the Equations of Table 5
OUTPUT RANGE
A4 • V
–2.5V to 7.5V
A3 • V
A4 • I
I
B1
SLEW
±2.5V
RATE
±10V
BIPOLAR ZERO
V/µs
0.25
0.16
10V
±5V
0.2
4.5
ERROR (LSB)
5V
22
22
OS1
OS2
B2
A4 •
• 0.13 •
• 0.13 •
• 19.6 •
• 13.1 •
0
A
VOL2
66
GAIN BANDWIDTH
V
5V
REF
V
V
V
5V
REF
PRODUCT
5V
5V
REF
REF
1.1
2.2
1.9
A1
MHz
0.75
12.5
2
4
1
0.8
0.7
90
90
I
V
V
B1
UNIPOLAR GAIN
OS1
I
OS2
B2
ERROR (LSB)
• 0.0018 •
A5 •
• 0.26 •
A2
• 13.1 •
• 26.2 •
2
3
2
4
1
3
A
131
VOL2
A
with LTC2752
131
VOL1
t
V
SETTLING
V
V
V
5V
0.83
REF
5V
REF
120
120
115
0.5
1.4
0.7
5V
5V
A3
REF
REF
µs
19
1
1
2
2
V
V
I
B1
OS1
I
OS2
B2
BIPOLAR GAIN
ERROR (LSB)
• 0.0018 •
0.5
A5 •
A4
• 0.26 •
1
1
1
• 13.1 •
• 26.2 •
DISSIPATION
10.5/Op Amp
123/Op Amp
A
69/Op Amp
131
VOL2
POWER
A
mW
117
131
46
11
VOL1
V
V
1.5
1.5
2.5
1.5
V
A5
5V
V
5V
REF
1
1
REF
5V
REF
5V
REF
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