AD1890/AD1891

–6–

REV. 0

Output Control Signals

Pin Name

Number

I/O

Description

BKPOL_O

19

I

Bit clock polarity. LO: Normal mode. Output data is valid on rising edges of BCLK_O, changed

on falling. HI: Inverted mode. Output data is valid on falling edges of BCLK_O, changed on rising.

TRGLR_O

18

I

Trigger on LR_O. HI: Changes in LR_O indicate beginning

edge of WCLK_O indicates beginning of valid output data.

MSBDLY_O 17

I

MSB delay. HI: Output data is delayed one BCLK_O after either LR_O (TRGLR_O = HI) or

WCLK_O (TRGLR_O = LO) indicates the beginning of valid output data. Included for I

format compatibility. LO: No delay.

Miscellaneous

Pin Name

Number

I/O

Description

GPDLYS

1

I

AD1890 ONLY: Group delay—short. HI: Short group delay mode (

≈700 µs). More sensitive to

changes in sample rates (LR clocks). LO: Long group delay mode (

≈3 ms). More tolerant of

sample rate changes. This signal may be asynchronous with respect to MCLK, and dynamically

changed, but is normally pulled up or pulled down on a static basis. AD1891: Short group delay

mode only; this pin is a N/C.

MCLK

2

I

56 kHz. Exact frequency is not critical, and does not need to be synchronized to any other clock

or possess low jitter.

RESET

13

I

Active LO reset. Set HI for normal chip operation.

MUTE_O

16

O

Mute output. HI indicates that data is not currently valid due to read and write FIFO memory

pointer overlap. LO indicates normal operation.

MUTE_I

15

I

Mute input. HI mutes the serial output to zeros (midscale). Normally connected to MUTE_O.

Reset LO for normal operation.

SETLSLW

28

I

Settle slowly to changes in sample rates. HI: Slow-settling mode (

≈800 ms). Less sensitive to

sample clock jitter. LO: Fast-settling mode (

≈200 ms). Some narrow-band noise modulation may

result from jitter on LR clocks. This signal may be asynchronous with respect to MCLK, and

dynamically changed, but is normally pulled up or pulled down on a static basis.

N/C

9, 20

No connect. Reserved. Do not connect.

Power Supply Connections

Pin Name

Number

I/O

Description

7, 22

I

Positive digital voltage supply.

GND

8, 14, 21, 27

I

Digital ground. Pins 14 and 27 need not be decoupled.

NOTE