Datasheet

LTC2752
20
2752f
applicaTions inForMaTion
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
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 A1 A2 A3 A4 A5
5V 1.1 2 1 1
10V 2.2 3 0.5 1.5
±5V 2 2 1 1 1.5
±10V 4 4 0.83 1 2.5
±2.5V 1 1 1.4 1 1
–2.5V to 7.5V 1.9 3 0.7 0.5 1.5
A3 • V
OS1
• 19.6 •
I
B1
• 0.13 •
0
A4 • V
OS2
• 13.1 •
A4 • I
B2
• 0.13 •
A4 •
 
5V
V
REF
 
5V
V
REF
 
16.5
A
VOL1
V
OS1
(mV)
I
B1
(nA)
A
VOL1
(V/mV)
V
OS2
(mV)
I
B2
(nA)
A
VOL2
(V/mV)
OP AMP
V
OS1
• 3 •
I
B1
• 0.0003 •
A1 •
0
0
0
INL (LSB)
 
5V
V
REF
 
5V
V
REF
 
1.5
A
VOL1
 
66
A
VOL2
 
131
A
VOL1
 
131
A
VOL1
 
131
A
VOL2
 
131
A
VOL2
V
OS1
• 0.78 •
I
B1
• 0.00008 •
A2 •
0
0
0
DNL (LSB)
 
5V
V
REF
 
5V
V
REF
A3 • V
OS1
• 13.1 •
I
B1
• 0.13 •
0
0
0
0
UNIPOLAR
OFFSET (LSB)
 
5V
V
REF
 
5V
V
REF
 
5V
V
REF
V
OS1
• 13.1 •
I
B1
• 0.0018 •
A5 •
V
OS2
• 26.2 •
I
B2
• 0.26 •
BIPOLAR GAIN
ERROR (LSB)
 
5V
V
REF
 
5V
V
REF
 
 
 
5V
V
REF
 
5V
V
REF
BIPOLAR ZERO
ERROR (LSB)
UNIPOLAR GAIN
ERROR (LSB)
 
5V
V
REF
 
5V
V
REF
 
5V
V
REF
 
5V
V
REF
 
5V
V
REF
V
OS1
• 13.1 •
I
B1
• 0.0018 •
A5 •
V
OS2
• 26.2 •
I
B2
• 0.26 •
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
AMPLIFIER SPECIFICATIONS
V
OS
µV
I
B
nA
A
VOL
V/mV
VOLTAGE
NOISE
nV/√Hz
CURRENT
NOISE
pA/√Hz
SLEW
RATE
V/µs
GAIN BANDWIDTH
PRODUCT
MHz
t
SETTLING
with LTC2752
µs
POWER
DISSIPATION
mW
LT1001 25 2 800 10 0.12 0.25 0.8 120 46
LT1097 50 0.35 1000 14 0.008 0.2 0.7 120 11
LT1112 (Dual) 60 0.25 1500 14 0.008 0.16 0.75 115 10.5/Op Amp
LT1124 (Dual) 70 20 4000 2.7 0.3 4.5 12.5 19 69/Op Amp
LT1468 75 10 5000 5 0.6 22 90 2 117
LT1469 (Dual) 125 10 2000 5 0.6 22 90 2 123/Op Amp