AD9670EBZ datasheet(39/53 Pages) AD

39 / 53 page

AD9670

Data Sheet

Rev. A | Page 38 of 52

Table 23. Coefficient Block Mapping into SPI Memory Location

Coefficients (8 Words × 14 Bits)

C7[13:0]

C6[13:0]

C5[13:0]

C4[13:0]

C3[13:0]

C2[13:0]

C1[13:0]

C0[13:0]

111:98

97:84

83:70

69:56

55:42

41:28

27:14

13:0

SPI Memory (14 Bytes)

B13[7:0]

B12[7:0]

B11[7:0]

B10[7:0]

B9[7:0]

B8[7:0]

B7[7:0]

B6[7:0]

B5[7:0]

B4[7:0]

B3[7:0]

B2[7:0]

B1[7:0]

B0[7:0]

111:104

103:96

95:88

87:80

79:72

71:64

63:56

55:48

47:40

39:32

31:24

23:16

15:8

7:0

DIGITAL TEST WAVEFORMS

Digital test waveforms can be used in the digital processing block

instead of the ADC output. The digital test waveforms enable is

set in Register 0x11B. Each channel can be individually enabled

in Register 0x11A.

Waveform Generator

For testing and debugging, use the programmable waveform

generator instead of ADC data. The waveform generator varies

offset, amplitude, and frequency. The generator uses the ADC

sample frequency, fSAMPLE, and ADC full-scale amplitude, AFULLSCALE,

as references. The values are set in Register 0x117, Register 0x118,

and Register 0x119 (see Table 27).

x = C + A × sin(2 × π × N)

(10)

N =

fSAMPLE 

(see Register 0x117)

(11)

A =

SCALE

FULL

(see Register 0x118)

(12)

C = AFULL SCALE × a × 2−(13 − b) (see Register 0x119)

(13)

Channel ID and Ramp Generator

In Channel ID test mode, the output is a concatenated value.

Output Data Bits[6:0] are a ramp. Output Data Bit 7 is 0 in real

data mode or I channel and 1 for Q channel in complex data

mode. Output Data Bits[10:8] are the channel ID such that

Channel A is coded as 000 and Channel B is 001. Output Data

Bits[15:11] are the chip address.

Filter Coefficients

To check the filter coefficients, the input to the decimating FIR

filter must be a sequence of 1 followed by 0s. The number of zeros

is the decimation rate times the number of taps (16). The output

shifter outputs the LSBs of the filter.

DIGITAL BLOCK POWER SAVING SCHEME

To reduce power consumption in the digital block, the

demodulator and decimation filter start in an idle state after

running the chip (Register 0x008, Bits[2:0] = 000). The digital

block only switches to a running state when the negative edge of

the TX_TRIG pulse is detected, or with a software TX_TRIG write

(Register 0x10C, Bit 5 = 1).

To put the digital block back into the idle state while the rest of

the chip is still running and to save power, enact one of the

following three events: raise the TX_TRIG signal high, write to

the profile index (Register 0x10C, Bits[4:0]), or the power stop

expires if the advanced power control feature is used. Figure 52

illustrates the digital block power saving scheme.

CHIP IN POWER-DOWN,

STANDBY,

OR CW MODE

DIGITAL

DEMODULATOR

IDLE

DIGITAL

DEMODULATOR

RUNNING

RUN CHIP

NEGATIVE EDGE TX_TRIG

OR S/W TX_TRIG

TX_TRIG IS HIGH, PROFILE

INDEX WRITE, OR POWER

STOP EXPIRES

Figure 52. Digital Block Power Saving Scheme

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