AD9779 Analog Devices, AD9779 Datasheet - Page 31

• Manufacturer Part Number: AD9779
• Description: Dual 16-Bit, 1 GSPS, Digital-to-Analog Converter
• Manufacturer: Analog Devices

Specifications of AD9779

• Resolution (bits): 16bit
• Dac Update Rate: 1GSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): +3.47V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

INTERPOLATION FILTER ARCHITECTURE
The AD9776/AD9778/AD9779 can provide up to 8× interpola-
tion, 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 13, Table 14, Table 15,
and Table 16. Spectral plots for the filter responses are shown in
Figure 57, Figure 58, and Figure 59.
Table 13. Half-Band 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)
Table 14. Half-Band 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)
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)
Upper Coefficient
H(23)
H(22)
H(21)
H(20)
H(19)
H(18)
H(17)
H(16)
H(15)
H(14)
H(13)
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
−2
0
+17
0
−75
0
+238
0
−660
0
+2530
+4096
Integer Value
Rev. A | Page 31 of 56
Table 15. Half-Band Filter 3
Lower Coefficient
H(1)
H(2)
H(3)
H(4)
H(5)
H(6)
H(7)
H(8)
Table 16. 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
Figure 58. 4× Interpolation, Low-Pass Response to ±4× Input Data Rate
–100
–100
–10
–20
–30
–40
–50
–60
–70
–80
–90
–10
–20
–30
–40
–50
–60
–70
–80
–90
10
10
0
0
–4
–4
–3
–3
(Dotted Lines Indicate 1 dB Roll-Off)
(Dotted Lines Indicate 1 dB Roll-Off)
–2
–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)
AD9776/AD9778/AD9779
f
f
OUT
OUT
–1
–1
(× Input Data Rate)
(× Input Data Rate)
0
0
1
1
Integer Value
−39
0
+273
0
−1102
0
+4964
+8192
Integer Value
+2
−4
+10
−35
+401
2
2
3
3
4
4