©2009 CADEKA Microcircuits LLC

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22

PRELIMINARY Data Sheet

Figure 6. Phase Programmability Modes for LCLK

The device can also be made to operate in SDR mode by setting the

en_sdr bit to '1'. The bit clock (LCLK) is output at

12x times the input clock in this mode, two times the rate in DDR mode. Depending on the state of

fall_sdr, LCLK may

be output in either of the two manners shown in Figure 7. As can be seen in Figure 7, only the LCLK rising (or falling)

edge is used to capture the output data in SDR mode. The SDR mode is not recommended beyond 40MSPS because the

LCLK frequency becomes very high.

EN_SDR=’1’, FALL_SDR_’0’

EN_SDR=’1’, FALL_SDR_’1’

FCLKN

FCLKP

LCLKP

LCLKN

Dxx<1:0>

FCLKN

FCLKP

LCLKN

LCLKP

Dxx<1:0>

Figure 7. SDR Interface Modes

The default data output format is offset binary. Two's complement mode can be selected by setting the

btc_mode bit to

'1' which inverts the MSB.

The first bit of the frame (following the rising edge of FCLKP) is the LSB of the ADC output for default settings. Program-

ming the

msb_first mode results in reverse bit order, and the MSB is output as the first bit following the FCLKP rising edge.

Table 14. Number of Serial Output Bits

Name

Description

Default

D

1

5

D

1

4

D

1

3

D

1

2

D

1

1

D

1

0

D

9

D

8

D

7

D

6

D

5

D

4

D

3

D

2

D

1

D

0

Address

In Hex

lvds_num_bits

Sets the number if LVDS output bits 12-bit

X 0

53

The ADCs have 13-bit resolution. There are two options for the serial LVDS outputs, 12 bits or 14 bits, selected by reg-

ister values '00' and '10', respectively. In 12-bit mode, the LSB bit from the ADCs are removed in the output stream. In

14-bit mode, a '0' is added in the LSB position. Power down mode must be activated after or during a change in the

number of output bits.

PHASE_DDR<1:0>=’00’

PHASE_DDR<1:0>=’10’

PHASE_DDR<1:0>=’01’

PHASE_DDR<1:0>=’11’

FCLKN

FCLKP

LCLKP

LCLKN

Dxx<1:0>

FCLKN

FCLKP

LCLKN

LCLKP

Dxx<1:0>

FCLKN

FCLKP

LCLKN

LCLKP

Dxx<1:0>

FCLKN

FCLKP

LCLKP

LCLKN

Dxx<1:0>