lmp7312max National Semiconductor Corporation, lmp7312max Datasheet - Page 13

• Manufacturer Part Number: lmp7312max
• Description: Lmp7312 Precision Spi-programmable Afe With Differential/single-ended Input/output
• Manufacturer: National Semiconductor Corporation

Application Section
GENERAL DESCRIPTION
The LMP7312 is a single supply programmable gain differ-
ence amplifier with two input pairs: Attenuation pair (-V
+V
configured in both single-ended and differential modes with
the output common mode voltage set by the user. The input
selection, the gains and the mode of operation of the
LMP7312 are controlled through a 4- wire SPI interface (SCK,
CS, SDI, SDO). These features combined make the
LMP7312 a very easy interface between the analog high volt-
age industrial buses and the low voltage digital converters.
OUTPUT MODE CONFIGURATION
The LMP7312 is able to work in both single ended and differ-
ential output mode. The selection of the mode is made
through the V
Differential Output
This mode of operation is enabled when the output common
mode voltage pin (V
IN
) and Amplification pair (-IN, +IN). The output can be
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(output common mode voltage) pin.
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) is connected to a voltage higher than
FIGURE 1. Differential ADC Interfacing with V
IN
,
13
1V, for instance the common mode voltage supplied by an
ADC,
floating an internal voltage divider biases it at the half supply
voltage. In this configuration the output signals are set on the
V
Single-Ended Output
This mode of operation is enabled when the V
to a voltage less than 0.5 V, for example to ground. In this
mode of operation the LMP7312 behaves as a difference am-
plifier, where the +V
the –V
1.
2.
In both cases the inverting output pin is configured as an input
pin.
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In the case of bipolar input signal the non inverting output
will be connected to an external reference through a
buffer
In the case of unipolar input signal the non inverting
output will be connected to ground
voltage level.
(Figure
OUT
CM
/V
provided by the ADC
(Figure
R
1) or a voltage reference. If the V
is the reference voltage.
2).
OUT
pin is the single-ended output while
(Figure
30075503
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3).
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pin is tied
pin is