Datasheet

ADC78H89
SNAS201D –APRIL 2003–REVISED MARCH 2013 www.ti.com
Figure 22. ADC78H89 in Hold Mode
ADC78H89 TRANSFER FUNCTION
The output format of the ADC89H89 is straight binary. Code transitions occur midway between successive
integer LSB values. The LSB width for the ADC78H89 is AV
DD
/ 4096. The ideal transfer characteristic is shown
in Figure 23.
Figure 23. Ideal Transfer Characteristic
TYPICAL APPLICATION CIRCUIT
A typical application of the ADC78H89 is shown in Figure 24. The split analog and digital supplies are both
provided in this example by the Texas Instruments LP2950 low-dropout voltage regulator, available in a variety of
fixed and adjustable output voltages. The analog supply is bypassed with a capacitor network located close to
the ADC78H89. The digital supply is separated from the analog supply by an isolation resistor and conditioned
with additional bypass capacitors. The ADC78H89 uses the analog supply (AV
DD
) as its reference voltage, so it
is very important that AV
DD
be kept as clean as possible. Because of the ADC78H89's low power requirements, it
is also possible to use a precision reference as a power supply to maximize performance. The four-wire interface
is also shown connected to a microprocessor or DSP.
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