Datasheet 搜索 > 开发套件 > TI（德州仪器） > TMP122EVM 数据手册 > TMP122EVM 产品设计参考手册 3/5 页
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TMP122EVM 产品设计参考手册 - TI（德州仪器）
制造商:
TI（德州仪器）
分类:
开发套件
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TMP122EVM数据手册
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CIRCUIT DESCRIPTION
The TMP122EVM is designed to be as simple as possible. It derives power from the RS-232 port to which it
is connected, and interfaces the TMP122’s SPI connection to the RS-232 port using a FET pair and an op-
amp.
Only three inputs from the computer are available, but this is enough to control the TMP122. One pin, DTR,
is used to supply power for the board. When at positive voltage, most systems will generate 10V to 12V,
which is enough to drive low-dropout regulator U3 through reverse-voltage protection diode D1B. A regulator
with extremely low quiescent current was chosen for this.
To control SCL and SDA, the DSR and transmit-data lines are used. Dual MOSFET Q1 is used to translate
the high voltage RS-232 levels into the TMP122’s logic levels. The pull-up resistors R1 and R2 are made
relatively large so as to consume minimal current in the logic LOW state; since we communicate with the
device slowly, the slow rise times caused by these values are of no concern.
SCHEMATICS
D1B
NDC7002N
CS
ALERT
SDA
SCL
V
DD
NDC7002N
TPS77033
OPA244
TMP122
4(DTR)
6(DSR)
7(RTS)
5(SG)
8(CTS)
3(TD)
10k
10k
100k
100k
10k
MA4X713
MA4X713
R7
D2
47K
Q1A
0.47
R1 R2
C4
Q1B
R3
R4
D1A
C5
C1
0.47
0.47
R6
U1
U2
U3
TP1
TP2
GNR
C3
10u
1 6
4
2
5
3
1
5
4
3
2
1
3
5
2
J2
J3
NDC7002N
Q2A
10k
R5
R8
1(DCD)
10k
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