LMH6521SQ/NOPB National Semiconductor, LMH6521SQ/NOPB Datasheet - Page 15

• Manufacturer Part Number: LMH6521SQ/NOPB
• Manufacturer: National Semiconductor

Specifications of LMH6521SQ/NOPB

• Lead Free Status / Rohs Status: Compliant

SDO is the data output pin and is normally at TRI-STATE
and is driven only when SCSb is asserted. Upon SCSb as-
sertion, contents of the register addressed during the first byte
are shifted out with the second 8 SCLK falling edges. Upon
power-up, the default register address is 00h
The SDO internal driver circuit is an open collector device with
a weak pull-up resistor to an internal 2.5V reference. It is 5V
tolerant so an external pull-up resistor can connect to 2.5V,
3.3V or 5V as shown in
up resistor should be chosen to limit the current to 11mA or
less. Otherwise the SDO logic low output level (V
R/Wb
Reserved Not used. Must be set to 0.
ADDR:
DATA
Read / Write bit. A value of 1 indicates a read
operation, while a value of 0 indicates a write
operation.
Address of register to be read or written.
In a write operation the value of this field will be
written to the addressed register when the chip
select pin is deasserted. In a read operation this
field is ignored.
Figure
11. However, the external pull-
FIGURE 10. Serial Interface Protocol (SPI compatible)
OL
may not
®
15
achieve close to ground and in extreme case could cause
problem for FPGA input gate. Using minimum values for ex-
ternal pull-up resistor is a good to maximize speed for SDO
signal. So if high SPI clock frequency is needed then minimum
value external pull-up resistor is the best choice as shown in
Figure
Each serial interface access cycle is exactly 16 bits long as
shown in
The read timing is shown in
is shown in figure
C7
0= write
1=read
Enable Gb5
0=Off
1=On
11.
1=
+16dB
Figure
Serial Word Format for LMH6521 (cont)
Serial Word Format for LMH6521
C6
0
10. Each signal's function is described below.
Gb4
1=
+8dB
Figure
C5
0
Gb3
1=
+4dB
13.
C4
0
Figure
C3
0
Gb2
1=
+2dB
12, while the write timing
C2
0
Gb1
1=
+1dB
C1
0
30120112
Gb0
1=
+0.5dB
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C0
0=Ch A
1=Ch B
RES
0