AD9776A Analog Devices, AD9776A Datasheet - Page 33

• Manufacturer Part Number: AD9776A
• Description: Dual 12-Bit, 1 GSPS, Digital-to-Analog Converter
• Manufacturer: Analog Devices

Specifications of AD9776A

• Resolution (bits): 12bit
• Dac Update Rate: 1GSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): +3.47V
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: Par

INTERPOLATION FILTER ARCHITECTURE
The AD9776A/AD9778A/AD9779A can provide up to 8× inter-
polation, or the interpolation filters can be entirely disabled. It
is important to note that the input signal should be backed off
by approximately 0.01 dB from full scale to avoid overflowing
the interpolation filters. The coefficients of the low-pass filters
and the inverse sinc filter are given in Table 15, Table 16, Table 17,
and Table 18. Spectral plots for the filter responses are shown in
Figure 57, Figure 58, and Figure 59.
Table 15. Low-Pass Filter 1
Lower Coefficient
H(1)
H(2)
H(3)
H(4)
H(5)
H(6)
H(7)
H(8)
H(9)
H(10)
H(11)
H(12)
H(13)
H(14)
H(15)
H(16)
H(17)
H(18)
H(19)
H(20)
H(21)
H(22)
H(23)
H(24)
H(25)
H(26)
H(27)
H(28)
Upper Coefficient
H(55)
H(54)
H(53)
H(52)
H(51)
H(50)
H(49)
H(48)
H(47)
H(46)
H(45)
H(44)
H(43)
H(42)
H(41)
H(40)
H(39)
H(38)
H(37)
H(36)
H(35)
H(34)
H(33)
H(32)
H(31)
H(30)
H(29)
Integer Value
−4
0
+13
0
−34
0
+72
0
−138
0
+245
0
−408
0
+650
0
−1003
0
+1521
0
−2315
0
+3671
0
−6642
0
+20,755
+32,768
Rev. B | Page 33 of 56
Table 16. Low-Pass Filter 2
Lower Coefficient
H(1)
H(2)
H(3)
H(4)
H(5)
H(6)
H(7)
H(8)
H(9)
H(10)
H(11)
H(12)
Table 17. Low-Pass Filter 3
Lower Coefficient
H(1)
H(2)
H(3)
H(4)
H(5)
H(6)
H(7)
H(8)
Table 18. Inverse Sinc Filter
Lower Coefficient
H(1)
H(2)
H(3)
H(4)
H(5)
Figure 57. 2× Interpolation, Low-Pass Response to ±4× Input Data Rate
–100
–10
–20
–30
–40
–50
–60
–70
–80
–90
10
0
–4
–3
(Dotted Lines Indicate 1 dB Roll-Off)
AD9776A/AD9778A/AD9779A
–2
Upper Coefficient
H(15)
H(14)
H(13)
H(12)
H(11)
H(10)
H(9)
Upper Coefficient
H(9)
H(8)
H(7)
H(6)
Upper Coefficient
H(23)
H(22)
H(21)
H(20)
H(19)
H(18)
H(17)
H(16)
H(15)
H(14)
H(13)
f
OUT
–1
(× Input Data Rate)
0
1
Integer Value
−39
0
+273
0
−1102
0
+4964
+8192
Integer Value
+2
−4
+10
−35
+401
2
Integer Value
−2
0
+17
0
−75
0
+238
0
−660
0
+2530
+4096
3
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