Datasheet

Data Sheet ADT7470
Rev. E | Page 13 of 40
TEMPERATURE MEASUREMENT USING TMP05/TMP06
MEASURING TEMPERATURE
The ADT7470 can be connected with up to 10 daisy-chained
TMP05/TMP06 devices for temperature measurement. Each
TMP05/TMP06 performs an ambient temperature measure-
ment, and outputs a PWM signal. The ADT7470 decodes the
PWM into a temperature measurement, and stores the result
in the temperature reading registers, listed in Table 7.The
maximum temperature read back from all TMP05 temperature
readings is stored in register 0x78.
To use the ADT7470 with TMP05/TMP06, the parts should be
connected as shown in Figure 13. Pin 13 on the ADT7470
should be configured as TMP_START, by s etting Configuration
Register 1 Bit 7 to Bit 1. (Register address 0x40 Bit[7] =1). The
start pulse required by the TMP05/06 will be output on the
TMP_START pin. The OUT pin on the last TMP05/06 in the
daisy-chain should be connected to Pin 12 on the ADT7470,
TMP_IN. For more information on the TMP05/06, refer to the
TMP05/TMP06 data sheet.
Reporting of 8-bit temperature values occurs only if the
TMP_IN function is used and if TMP05/TMP06s are daisy-
chained according to their data sheet and connected as shown.
The ADT7470 does not have any temperature measurement
capability when used as a standalone device without TMP05s
and TMP06s connected.
Table 7. Temperature Reading Registers
Register Reading Default
0x20 Temperature 1 reading 0x00
0x21
Temperature 2 reading
0x00
0x22 Temperature 3 reading 0x00
0x23 Temperature 4 reading 0x00
0x24 Temperature 5 reading 0x00
0x25 Temperature 6 reading 0x00
0x26 Temperature 7 reading 0x00
0x27 Temperature 8 reading 0x00
0x28 Temperature 9 reading 0x00
0x29 Temperature 10 reading 0x00
0x78 Max TMP05 temperature 0x00
TMP05/TMP06 Decoder
The ADT7470 includes a PWM processing engine to decode the
daisy-chained PWM output from multiple TMP05s and TMP06s.
It then passes each decoded temperature value to the temper-
ature value registers. This allows the ADT7470 to do high/
low limit comparisons of temperature and to automatically
control fan speed based on measured temperature. The PWM
processing engine contains all necessary logic to initiate start
conversions on the first daisy-chained TMP05/TMP06 and
to synchronize with each temperature value as it is fed back to
the device through the daisy chain. The start function is multi-
plexed onto the same pin that can be used to blast the fans
to full speed. The start conversion for TMP05/TMP06 temp-
erature measurement is fully transparent to the user and does
not require any software intervention to function.
NO. 1
CONV/IN
OUT
NO. 2
CONV/IN
OUT
NO. 3
NO. n
CONV/IN
OUT
CONV/IN
OUT
04684-0-013
TMP05/
TMP06
TMP05/
TMP06
TMP05/
TMP06
TMP05/
TMP06
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
V
CC
TACH3
TACH2
TACH1
PWM2
SCL
PWM1
SMBALERT
PWM4
PWM3 TACH4
ADDR
TMP_IN
SDA
ADT7470
FULL_SPEED/TMP_START
Figure 13. Interfacing the ADT7470 to Multiple Daisy-Chained TMP05/TMP06 Temperature Sensors