ADC34RF72 datasheet(40/74 Pages) TI2

40 / 74 page

7.3.5.5.4 Numerically Controlled Oscillator (NCO)

FS = ADC sampling rate (MSPS)

Each digital down-converter (DDC) uses a 48-bit numerically controlled oscillator (NCO) to fine tune the

frequency placement prior to the digital filtering as shown in Figure 7-30. The NCO frequency range is -FS/2

to FS/2 and is dictated by a frequency control word (FCW) and phase offset.

There are two different NCO frequencies for each DDC. The desired NCO frequency is programmed via SPI and

can be selected using SPI or the GPIO pins. When using the GPIO pins for NCO frequency control, frequency

hopping can be achieved in less than 1µs.

NCO1[7:0]

nco1_fcw[7:0]

nco1_phase[7:0]

nco_hop_mode[7:0]

NCO0[7:0]

nco_update[7:0]

nco0_fcw[7:0]

nco0_phase[7:0]

±j n

gpio_nco_sel[7:0]

sw_nco_sel[7:0]

mixer_nco_sel[7:0]

nco_hop_src_sel[7:0]

nco_reset[7:0]

Figure 7-30. NCO block diagram with all control signals

Infinite Phase Coherent NCO: With a phase coherent NCO, all frequencies are synchronized to a single event

using SYSREF. This enables an infinite amount of frequency hops without the need to reset the NCO as phase

coherency is maintained between frequency hops. This is illustrated in Figure 7-31 (right). When returning to the

original frequency f1, the NCO phase appears as if the NCO had never changed frequencies.

Figure 7-31. Infinite Phase Coherent NCO Frequency Switching

ADC32RF72

SBASAL2 – NOVEMBER 2025

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ADC34RF72 Datasheet(PDF) 40 Page - Texas Instruments