TMP01GBC AD [Analog Devices], TMP01GBC Datasheet - Page 12

• Manufacturer Part Number: TMP01GBC
• Description: Low Power, Programmable Temperature Controller
• Manufacturer: AD [Analog Devices]

TMP01
Buffering the Temperature Output Pin
The VPTAT sensor output is a low impedance dc output volt-
age with a 5 mV/K temperature coefficient, and is useful in a
number of measurement and control applications. In many ap-
plications, this voltage needs to be transmitted to a central loca-
tion for processing. The buffered VPTAT voltage output is
capable of 500 A drive into 50 pF (max). As mentioned in the
discussion above regarding buffering circuits for the VREF out-
put, it is useful to consider external amplifiers for interfacing
VPTAT to external circuitry to ensure accuracy, and to mini-
mize loading which could create dissipation-induced tempera-
ture sensing errors. An excellent general-purpose buffer circuit
using the OP177 is shown in Figure 17 which is capable of driv-
ing over 10 mA, and will remain stable under capacitive loads of
up to 0.1 F. Other interfacing ideas are shown below.
Differential Transmitter
In noisy industrial environments, it is difficult to send an accu-
rate analog signal over a significant distance. However, by send-
ing the signal differentially on a wire pair, these errors can be
significantly reduced. Since the noise will be picked up equally
on both wires, a receiver with high common-mode input rejec-
tion can be used to cancel out the noise very effectively at the
R1
R2
R3
1
2
3
4
VREF
HYSTERESIS
GENERATOR
Figure 18. Send the Signal Differentially for Noise Immunity
TEMPERATURE
COMPARATOR
REFERENCE
SENSOR &
VOLTAGE
WINDOW
TMP01
VPTAT
8
7
6
5
VPTAT
V+
10k
–12–
10k
10k
OP297
OP297
receiving end. Figure 18 shows two amplifiers being used to
send the signal differentially, and an excellent differential
receiver, the AMP03, which features a common-mode rejection
ratio of 95 dB at dc and very low input and drift errors.
1/2
1/2
R1
R2
R3
Figure 17. Buffer VPTAT to Handle Difficult Loads
50
50
1
2
3
4
VREF
HYSTERESIS
GENERATOR
TEMPERATURE
COMPARATOR
REFERENCE
SENSOR &
VOLTAGE
WINDOW
TMP01
VPTAT
V+
V–
8
7
6
5
AMP03
V+
VPTAT
V
OUT
0.1 F
V+
V–
10k
OP177
100
REV. C
C
V
L
OUT