LMP8100 Datasheet, PDF (25/30 Pages) National Semiconductor (TI) – Programmable Gain Amplifier

The serial control pins can be connected in one of two ways
when two or more LMP8100s are used in an application.
Star Configuration
This configuration can be used if each LMP8100 will always
have the same value in each register. The connections are
shown in Figure 14. After the microcontroller writes a byte all
registers will have the same value.
FIGURE 14. Star Configuration
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Daisy Chain Configuration
lowing LMP8100. The following two examples show how the
This configuration can be used to program the same or dif-
registers are written.
ferent values in the register of each LMP8100. The connec-
tions are shown in Figure 15. In this configuration the SDO
pin of each LMP8100 is connected to the SDI pin of the fol-
If all three LMP8100s need a gain of 11 with a compensation level of 10. (10001010)
Register of
LMP8100 #1
Register of
LMP8100 #2
Register of
LMP8100 #3
Notes
Power on
00000000
00000000
00000000
Default power on state (see above)
Byte one sent
Byte two sent
Byte three sent
10001010
10001010
10001010
00000000
10001010
10001010
00000000
00000000
10001010
The data in the register of LMP8100 #1 is
shifted into the register of LMP8100 #2, the
data in the register of LMP8100 #2 is shifted
into the register of LMP8100 #3.
If LMP8100 #1 needs a gain of 11 with a compensation level of 10 (10001010), LMP8100 #2 needs a gain of 6 with a compensation
of 00 (00000101), and LMP8100 #3 needs a gain of 2 with a compensation of 00 (00000001).
Register of
LMP8100 #1
Register of
LMP8100 #2
Register of
LMP8100 #3
Notes
Power on
00000000
00000000
00000000
Default power on state (see above)
Byte one sent
Byte two sent
Byte three sent
00000001
00000101
10001010
00000000
00000001
00000101
00000000
00000000
00000001
The data in the register of LMP8100 #1 is
shifted into the register of LMP8100 #2, the
data in the register of LMP8100 #2 is shifted
into the register of LMP8100 #3.
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