lm96530sqx National Semiconductor Corporation, lm96530sqx Datasheet - Page 7

• Manufacturer Part Number: lm96530sqx
• Description: Lm96530 Ultrasound Transmit/receive Switch
• Manufacturer: National Semiconductor Corporation

DAISY CHAINING MULTIPLE LM96530 ICs
For connecting multiple T/R switch ICs, the LM965XX SPI™-
compatible bus can be daisy-chained up to 16 ICs at 10MHz
SCLKI for easy PCB routing. The inputs SDI, SCSI and SCLKI
are daisy-chained together with SDO, SCSO and SCLKO.
Therefore, the next IC’s SDI is connected to the previous IC’s
SDO. Similarly, the next IC’s SCSI is connected to the previ-
ous IC’s SCSO, and the next IC’s SCLKI is connected to the
previous IC’s SCLKO, as shown in . Daisy-chaining multiple
LM96530 devices amounts to one large shift register with the
number of bits being equal to 8 times the number of LM96530
BASIC OPERATION WITHOUT SERIAL INTERFACE
COMMUNICATION
To disable the SPI™ compatible interface, connect the pin
SPI_EN to AGND. To reverse bias all 8 channels of the T/R
switch, connect the pin, SW_OFF to VLL. To forward bias all
8 channels of the T/R switch, connect the pin, SW_OFF to
AGND.
FIGURE 3. 16 LM96530 Devices Daisy Chained @ SCLKI = 16MHz
7
ICs. For example, if 3 LM96530 ICs are daisy-chained, one
can picture a 24–bit shift register. Thus, the MSB or first bit
written on the SDI line (D23) will control channel 7 of the last
LM96530, i.e., the IC that is daisy-chained the farthest away
from the SPI master. The LSB or last bit written on the SDI
line (D0) will control channel 0 of the first LM96530, i.e., the
IC that is closest to the SPI master. It is important to note that
If only one particular channel of an IC in the daisy-chain re-
quires updating, all of the ICs, i.e., the entire shift register,
must be written to.
POWER-UP AND POWER-DOWN SEQUENCES
VSUB needs to always be the most negative supply – equal
to or more negative than VSS or the most negative transmit
pulse at all times. The power sequence should be to ap-
plied to VSUB first, followed by the remaining supplies in
any order.
30122006
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