TC1023 Datasheet, PDF (3/6 Pages) TelCom Semiconductor, Inc – PRECISION TEMPERATURE-TO-VOLTAGE CONVERTERS WITH SHUTDOWN MODE

PRECISION TEMPERATURE-TO-VOLTAGE
CONVERTERS WITH SHUTDOWN MODE
PRELIMINARY INFORMATION
TC1023
TC1024
DETAILED DESCRIPTION
A plot of output voltage versus temperature for both the
TC1023 and TC1024 appears in Figure 5. The TC1023 can
be used with single power supply to measure temperatures
from 0°C to 100°C. A pull-down resistor (R1 in Figure 1)
must be added from the output pin to the negative power
supply for measuring temperatures less than 0°C. The
value of the resistor must be chosen to limit the maximum
current pulled from the output to the negative supply to
– 50µA (i.e., R1 = V_SS/50µA).
V_CC = 3.0V to 12.0V
V_CC
V_OUT
CE ^TC1024
GND
V_OUT
Output Stage
Both devices have Class A output stages capable of
sourcing 1mA. These devices have a limited ability to drive
heavy capacitive loads. Loads of 50pF (to ground) can be
driven directly. For heavier loads, a 2kΩ (or greater) resis-
tor should be placed in series with the output for decoupling.
If the TC1023/1024 is used in a noisy electrical environ-
ment, a 0.1µF bypass capacitor from V_CC to GND is recom-
mended.
Shutdown/Calibrate Mode
The TC1023/1024 enters shutdown when the CE input
is taken to V_IH. This causes quiescent current to fall to 1µA
(typ) and the output to drop immediately to 0V through
approximately 100kΩ. For applications where the TC1023/
1024 is connected to an external A/D converter, a refer-
ence voltage can be directly connected to V_OUT while in
shutdown for A/D calibration, as shown in Figure 3. A
CMOS gate provides bias voltage to the bandgap refer-
ence V_R, and at the same time disables the TC102x by
taking CE to V_IH. Limiting resistor R1 should be chosen to
limit current through the voltage reference to the desired
current (I_REF). That is, R1 = (V_OH – V_REF)/I_REF (where V_OH
is the CMOS gate output high voltage at output current
equal to I_REF; and V_REF is the reference voltage of V_R).
V_CC = 2.2V to 12.0V MIN.
V_CC
V_OUT
TC1023
CE
GND
V_OUT
R1 = V_SS /50µA
TC1024 (– 20°C to +125°C)
Figure 2. TC1024 Connections
V_CC
2.5V
REF
V_CC
V_OUT
TC102x
CE
GND
A/D
CONVERTER
R1
CMOS
GATE
CAL
Figure 3. A/D Calibration
Multi-Zone Temperature Sensing
The CE input facilitates multi-zone temperature sens-
ing as shown in the example of Figure 4. In this example,
the processor addresses either of two sensors with a single
I/O port pin. The TC102x V_OUT pins are connected together
and routed to the processor's A/D converter, eliminating
the need for separate A/D input channels for each sensor.
V_CC
Zone 1
V_CC
V_OUT
TC102x
CE
GND
Zone 2
V_CC
V_OUT
TC102x
CE
GND
MICROCONTROLLER
A/D
CONVERTER
V_SS
Figure 1. TC1023 Connections
TC1023/1024-05 6/12/97
Zone 1/Zone 2
I/O Pin
Figure 4. TC1023/1024 Addressing
3