EMC1184 Datasheet, PDF (14/48 Pages) SMSC Corporation – Quad Channel 1°C Temperature Sensor with Beta

Quad Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications
Datasheet
4.1.3
Table 4.1 SMBus Address Decode (continued)
PULL UP RESISTOR ON
THERM PIN (±5%)
10k
15k
22k
33k
SMBUS ADDRESS
1001_100(r/w)b
1101_100(r/w)b
0011_100(r/w)b
0111_100(r/w)b
THERM Pin Considerations
Because of the decode method used to determine the SMBus Address, it is important that the pull-up
resistance on the THERM pin be within the tolerances shown in Table 4.1. Additionally, the pull-up
resistor on the THERM pin must be connected to the same 3.3V supply that drives the VDD pin.
For 15ms after power up, the THERM pin must not be pulled low or the SMBus address will not be
decoded properly. If the system requirements do not permit these conditions, the THERM pin must be
isolated from its hard-wired OR’d bus during this time.
One method of isolating this pin is shown in Figure 4.4, "Isolating the THERM pin".
+3.3V
+2.5 - 5V
VDD 1
DP1 ²
DN1 3
DP2 / DN3 4
DN2 / DP3 5
EMC1184
10 _SMCLK
9 _SMDATA
8 _{ALERT / THERM2}
7 _{THERM / ADDR}
6 ^GND
4.7K – 33k
22K
Shared Therm
4.1.5
4.1.6
Figure 4.4 Isolating the THERM pin
SMBus Data Bytes
All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.
SMBus ACK and NACK Bits
The SMBus client will acknowledge all data bytes that it receives. This is done by the client device
pulling the SMBus data line low after the 8th bit of each byte that is transmitted. This applies to the
Write Byte protocol.
The Host will NACK (not acknowledge) the last data byte to be received from the client by holding the
SMBus data line high after the 8th data bit has been sent.
Revision 1.0 (07-11-13)
14
DATASHEET
SMSC EMC1184