AD9139 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD9139

16-Bit, 1600 MSPS, TxDAC+ Digital-to-Analog Converter

Analog Devices 

AD9139

Table 16. Half-Band Filter 1 Coefficient

Lower Coefficient Upper Coefficient

H(1)

H(55)

H(2)

H(54)

H(3)

H(53)

H(4)

H(52)

H(5)

H(51)

H(6)

H(50)

H(7)

H(49)

H(8)

H(48)

H(9)

H(47)

H(10)

H(46)

H(11)

H(45)

H(12)

H(44)

H(13)

H(43)

H(14)

H(42)

H(15)

H(41)

H(16)

H(40)

H(17)

H(39)

H(18)

H(38)

H(19)

H(37)

H(20)

H(36)

H(21)

H(35)

H(22)

H(34)

H(23)

H(33)

H(24)

H(32)

H(25)

H(31)

H(26)

H(30)

H(27)

H(29)

H(28)

Integer Value

−4

0

+13

0

−32

0

+69

0

−134

0

+239

0

−401

0

+642

0

−994

0

+1512

0

−2307

0

+3665

0

−6638

0

+20,754

+32,768

INVERSE SINC FILTER

The AD9139 provides a digital inverse sinc filter to compensate

for the DAC rolloff over frequency. The inverse sinc (sinc−1) filter

is a seven-tap FIR filter. Figure 38 shows the frequency response

of sin(x)/x rolloff, the inverse sinc filter, and their composite

response. The composite response has less than ±0.05 dB pass-

band ripple up to a frequency of 0.4 × fDAC.

Data Sheet

To provide the necessary peaking at the upper end of the pass

band, the inverse sinc filter has an intrinsic insertion loss of

approximately 3.8 dB. Offset the loss of the digital gain by

increasing the digital gain adjustment setting to minimize the

impact on the output signal-to-noise ratio (SNR). However, care is

needed to ensure that the additional digital gain does not cause

signal saturation, especially at high output frequencies. The sinc−1

filter is disabled by default; it can be enabled by setting the

INVSINC_ENABLE bit to 1 in Register 0x27[7]).

1

0

–1

sin(x)/x ROLLOFF

–2

SINC–1 FILTER

COMPOSITE

–3

–4

–5

0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

FREQUENCY (Hz)

Figure 38. Responses of sin(x)/x Roll-Off (Blue), Sinc−1 Filter (Red), and

Composite of Both (Black)

Table 17. Inverse Sinc Filter

Lower Coefficient Upper Coefficient

H(1)

H(7)

H(2)

H(6)

H(3)

H(5)

H(4)

Integer Value

−1

+4

−16

+192

DIGITAL FUNCTION CONFIGURATION

The inverse sinc filter can be enabled or disabled. The pipeline

latency of the DAC is dependent on which of the digital

function blocks are enabled or disabled. If fixed DAC pipeline

latency is desired during operation, leave each digital function

block always enabled or always disabled after initial configuration.

Rev. A | Page 28 of 56

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