SM72445_15 Datasheet, PDF (15/20 Pages) Texas Instruments – SM72445 Programmable Maximum Power Point Tracking Controller With Adjustable PWM Frequency

SM72445
www.ti.com
SNVS795 – MARCH 2012
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91
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SCL
SDA
A6 A5 A4 A3 A2 A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Start by
Master
Frame 1
Serial Bus Address Byte
Ack
by
SM72445
Frame 2
Command
Register Byte
Ack Repeat
by Start by
SM72445 Master
SCL
(Continued)
SDA
(Continued)
1
91
9
A6 A5 A4 A3 A2 A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Ack
Ack
by
by
Frame 3
SM72445
Frame 4
Master
Serial Bus Address Byte
Length Byte = 7
SCL
(Continued)
SDA
(Continued)
1
91
9
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Ack
No Ack Stop
by
by
by
Frame 10
Master
Frame 11
Master Master
Data 6
Data 7
Figure 15. I2C Read Sequence
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91
9
SCL
SDA
A6 A5 A4 A3 A2 A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Start by
Master
Frame 1
Serial Bus Address Byte
Ack
by
SM72445
Frame 2
Command
Register Byte
Ack
by
SM72445
SCL
(Continued)
SDA
(Continued)
1
91
9
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Ack
Ack
by
by
Frame 3
SM72445
Frame 4
SM72445
Length Byte = 7
Data 1
SCL
(Continued)
SDA
(Continued)
1
91
9
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Ack
No Ack Stop
by
by
by
Frame 10
SM72445
Frame 11
SM72445 Master
Data 6
Data 7
Figure 16. I2C Write Sequence
Noise coupling into digital lines greater than 400 mVp-p (typical hysteresis) and undershoot less than 500 mV
below GND, may prevent successful I2C communication with SM72445. I2C no acknowledge is the most
common symptom, causing unnecessary traffic on the bus. Although the I2C maximum frequency of
communication is rather low (400 kHz max), care still needs to be taken to ensure proper termination within a
system with multiple parts on the bus and long printed board traces. Additional resistance can be added in series
with the SDA and SCL lines to further help filter noise and ringing. Minimize noise coupling by keeping digital
traces out of switching power supply areas as well as ensuring that digital lines containing high speed data
communications cross at right angles to the SDA and SCL lines.
Copyright © 2012, Texas Instruments Incorporated
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