Datasheet

ADS8556
ADS8557
ADS8558
www.ti.com SBAS404B –OCTOBER 2006– REVISED JANUARY 2012
TERMINAL FUNCTIONS
DESCRIPTION
NAME PIN # TYPE
(1)
PARALLEL INTERFACE (PAR/SER = 0) SERIAL INTERFACE (PAR/SER = 1)
Hardware mode (HW/SW = 0):
Reference buffers enable input.
When low, all reference buffers are enabled (mandatory if
internal reference is used). When high, all reference buffers
Data bit 14 input/output
DB14/REFBUF
EN
1 DIO/DI
are disabled.
Output is '0' for the ADS8557/8
Software mode (HW/SW = 1):Connect to BGND or BVDD.
The reference buffers are controlled by bit C24 (REFBUF) in
control register (CR).
Data bit 13 input/output Hardware mode (HW/SW = 0): Connect to BGND
DB13/SDI 2 DIO/DI Output is MSB for the ADS8557 and '0' for the
Software mode (HW/SW = 1): Serial data input
ADS8558
Data bit 12 input/output
DB12 3 DIO Connect to BGND
Output is '0' for the ADS8558
Data bit 11 input/output
DB11 4 DIO Connect to BGND
Output is MSB for the ADS8558
When SEL_C = 1, data output for channel C
DB10/SDO_C 5 DIO/DO Data bit 10 input/output
When SEL_C = 0, this pin should be tied to BGND
When SEL_B = 1, data output for channel B
When SEL_B = 0, this pin should be tied to BGND
DB9/SDO_B 6 DIO/DO Data bit 9 input/output
When SEL_C = 0, data from channel C1 are also available
on this output
Data output for channel A
When SEL_C = 0, data from channel C0 are also available
DB8/SDO_A 7 DIO/DO Data bit 8 input/output on this output
When SEL_C = 0 and SEL_B = 0, SDO_A acts as the single
data output for all channels
BGND 8 P Buffer IO ground, connect to digital ground plane
Buffer IO supply, connect to digital supply (2.7V to 5.5V). Decouple with a 1μF ceramic capacitor or a combination
BVDD 9 P
of 100nF and 10μF ceramic capacitors to BGND.
Word mode (WORD/BYTE = 0):
Data bit 7 input/output
Daisy-chain enable input.
Byte mode (WORD/BYTE = 1):
DB7/HB
EN
/DC
EN
10 DIO/DI/DI When high, DB[5:3] serve as daisy-chain inputs DCIN[A:C].
High byte enable input.
If daisy-chain mode is not used, connect to BGND.
When high, the high byte is output first on
DB[15:8]. When low, the low byte is output first on
DB[15:8].
Word mode (WORD/BYTE = 0):
Data bit 6 input/output
DB6/SCLK 11 DIO/DI Serial interface clock input (36MHz max)
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 5 input/output
When DC
EN
= 1, daisy-chain data input for channel A
DB5/DCIN_A 12 DIO/DI
When DC
EN
= 0, connect to BGND
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
When SEL_B = 1 and DC
EN
= 1, daisy-chain data input for
Data bit 4 input/output
DB4/DCIN_B 13 DIO/DI channel B
Byte mode (WORD/BYTE = 1):
When DC
EN
= 0, connect to BGND
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
When SEL_C = 1 and DC
EN
= 1, daisy-chain data input for
Data bit 3 input/output
DB3/DCIN_C 14 DIO/DI channel C
Byte mode (WORD/BYTE = 1):
When DC
EN
= 0, connect to BGND
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 2 input/output
Select SDO_C input.
DB2/SEL_C 15 DIO/DI
When high, SDO_C is active. When low, SDO_C is disabled.
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 1 input/output
Select SDO_B input.
DB1/SEL_B 16 DIO/DI
When high, SDO_B is active. When low, SDO_B is disabled.
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
(1) AI = analog input; AIO = analog input/output; DI = digital input; DO = digital output; DIO = digital input/output; and P = power supply.
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