NE5037 Ver la hoja de datos (PDF) - Philips Electronics
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NE5037 Datasheet PDF : 8 Pages
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Philips Semiconductors Linear Products
6-Bit A/D converter (parallel outputs)
Product specification
NE5037
APPLICATION
• 0 to 63°C Temperature Sensor
CIRCUIT DESCRIPTION
The temperature sensor of Figure 3 provides an input to Pin 3 of the
NE5037 of 32mV/°C. This 32mV is the value of one LSB for the
NE5037. The LM334 is a three-terminal temperature sensor and
provides a current of 1µA for each °Kelvin. The first section of the
dual op amp is connected as a trans-impedance amplifier to convert
the current from the LM334 to a voltage, which is amplified and
inverted by the section amplifier. Note that the first amplifier requires
different values of feedback resistance for °C and °F. The NE5512
was chosen for its low temperature coefficient of input bias current
as excessive IOS tempco would degrade temperature tracking.
To read temperature, conversion is started by sending a momentary
low signal to Pin 7 of the NE5037. When Pin 10 of the NE5037 goes
low, conversion is complete and a low is applied to Pin 9 of the
NE5037 to read data on Pins 11 through 16. Note that this
temperature data is in straight binary format.
The controller can be a microprocessor in a temperature control
application, or discrete circuitry in a simple temperature reporting
application. A temperature reporting (digital thermometer) circuit is
shown in Figure 3b. The NE5037 A/D converter is connected in a
continuous conversion mode by connecting together Pins 7, 9, and
10. Should this pin be momentarily shorted to any relatively low
impedance point, conversion will stop. Conversion will resume upon
interruption and restoration of the power. These pins are also
connected to the latch enable of a 6-bit latch because the data at the
converter output is available for only a short time when the converter
is in the continuous conversion mode. The (P)ROM) must have the
correct code for converting the data from the NE5037 (used as
address for the (P)ROMs) to the appropriate segment drive codes.
Note that the circuit of Figure 3b shows a circuit which can be used
to display either Fahrenheit or Centigrade temperatures.
The displayed output could easily be converted to degrees
Fahrenheit (°F) by the controller of Figure 3a or through the
(P)ROMs of Figure 3b. When doing this, a third (hundreds) digit
(P)ROM and display will be needed for displaying temperatures
above 99°F.
An inexpensive clock can be made from NAND gates or inverters,
as shown in Figure 3c.
CIRCUIT ADJUSTMENT
The circuit should be at a known ambient temperature for a few
minutes before making adjustments.
14.Adjust bias adjust potentiometer for the voltage indicated in the
chart in Figure 3b.
15.With the circuit (or sensor U3, if it is remotely located) at a known
temperature for 2 to 3 minutes, adjust range control for a correct
reading on the displays.
This should provide an accuracy of ±3 counts (3° F or C). Higher
accuracy may require NE5037 reference voltage regulation.
August 31, 1994
589
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