Datasheet

Data Sheet TMP05/TMP06
Rev. C | Page 15 of 28
The temperature equation for the high state conversion rate is
Temperature (°C) = 421 − (93.875 × (T
H
/T
L
)) (3)
Table 9. Conversion Times Using Equation 3
Temperature (°C) T
L
(ms) Cycle Time (ms)
–40 13.4 79.1
–30 13.7 79.6
–20 14.1 80.3
–10 14.6 81.4
0 15 82.2
10 15.3 82.5
20 16 83.6
25 16.1 83.9
30 16.4 84.7
40 16.9 85.7
50 17.5 86.8
60 18.1 87.8
70 18.7 88.5
80 19.3 89.7
90 20.1 91
100 21 93
110 21.9 94.5
120 22.8 96
130 23.8 97.8
140 24.9 99.4
150 26.1 101.4
Daisy-Chain Mode
Setting the FUNC pin to a high state allows multiple TMP05/
TMP06s to be connected together and, therefore, allows one input
line of the microcontroller to be the sole receiver of all temperature
measurements. In this mode, the CONV/IN pin operates as the
input of the daisy chain. In addition, conversions take place at
the nominal conversion rate of T
H
/T
L
= 34 ms/65 ms at 25°C.
Therefore, the temperature equation for the daisy-chain mode
of operation is
Temperature (°C) = 421 − (751 × (T
H
T
L
)) (4)
OUT
MICRO
IN
TMP05/
TMP06
CONV/IN
OUT
#1
TMP05/
TMP06
CONV/IN
OUT
#2
TMP05/
TMP06
CONV/IN
OUT
#3
TMP05/
TMP06
CONV/IN
OUT
#N
03340-009
Figure 24. Daisy-Chain Structure
A second microcontroller line is needed to generate the conver-
sion start pulse on the CONV/IN pin. The pulse width of the
start pulse should be less than 25 µs but greater than 20 ns. The
start pulse on the CONV/IN pin lets the first TMP05/TMP06
part know that it should now start a conversion and output its
own temperature. Once the part has output its own temperature,
it outputs a start pulse for the next part on the daisy-chain link.
The pulse width of the start pulse from each TMP05/TMP06 part
is typically 17 s.
Figure 25 shows the start pulse on the CONV/IN pin of the first
device on the daisy chain. Figure 26 shows the PWM output by
this first part.
Before the start pulse reaches a TMP05/TMP06 part in the
daisy chain, the device acts as a buffer for the previous tempera-
ture measurement signals. Each part monitors the PWM signal
for the start pulse from the previous part. Once the part detects
the start pulse, it initiates a conversion and inserts the result at
the end of the daisy-chain PWM signal. It then inserts a start
pulse for the next part in the link. The final signal input to the
microcontroller should look like Figure 27. The input signal on
Pin 2 (IN) of the first daisy-chain device must remain low until
the last device has output its start pulse.
If the input on Pin 2 (IN) goes high and remains high, the
TMP05/TMP06 part powers down between 0.3 sec and 1.2 sec
later. The part, therefore, requires another start pulse to generate
another temperature measurement. Note that to reduce power
dissipation through the part, it is recommended to keep Pin 2
(IN) at a high state when the part is not converting. If the IN pin
is at 0 V, the OUT pin is at 0 V (because it is acting as a buffer
when not converting), and is drawing current through either the
pull-up MOSFET (TMP05) or the pull-up resistor (TMP06).
MUST GO HIGH ONLY
AFTER START PULSE HAS
BEEN OUTPUT BY LAST
TMP05/TMP06 ON DAISY CHAIN.
START
PULSE
CONVERSION
STARTS ON
THIS EDGE
>20ns
AND
<25µs
TIME
T
0
>20ns
0
3340-017
Figure 25. Start Pulse at CONV/IN Pin of First
TMP05/TMP06 Device on Daisy Chain
START
PULSE
17µs
#1 TEMP MEASUREMENT
T
0
TIME
03340-010
Figure 26. Daisy-Chain Temperature Measurement
and Start Pulse Output from First TMP05/TMP06