Signal Definition

Analog Input Options

The analog input signal may be connected directly to the

VIN ADC input or go through a buffer amplifier.

Direct into VINADC

The input range can be from 0V to VREFIN. This input is

nominally high impedance but should be driven by a low

impedance source.

Input Through Buffer Amp

The HTADC12 has an integrated buffer amplifier which can

be used to condition the input signal. The access to the

amplifiers input pins and ability to create different circuits

is dependent on the package option selected.

14 Pin Package: The buffer amplifier is configured as a unity

gain amplifier with an input range of 0V to VREFIN. The output

should then be connected directly to the VIN_ADC pin.

R1 = R2 = 20k ohms.

28 Pin Package: With the 28 pin package, both input terminals

and the output terminal of the amplifier are available. On the

positive terminal, the AIN1 and AIN2 inputs are configured to

allow the signal to be divided by 2 through a resistor divider

(with either AIN1 or AIN2 connected to VSSA = 0V). This

provides the ability to use signals from 0V to 5V. The negative

input terminal and output are on separate pins allowing

additional circuits to be created. The maximum output value

shall be VREFIN. The internal resistor values are 20k ohms.

This output may then be connected to VIN ADC which has an

input range of 0V to VREFIN (or 2.5V maximum). The output

buffer may also be used as a unity-gain input buffer by applying

the analog input to both AIN1 and AIN2.

Tri-State Output Control

The digital outputs are tri-state drivers. They are controlled by

the CE, NCS, and RNC. To have the outputs active, CE and RNC

must be high and NCS must be low.

RNC

The RNC signal is used to trigger an A-to-D Conversion by a

high-to-low transition.

STS

This signal is a status indicator for the validity of the output data.

STS is high while a conversion is in progress.

NAP

The NAP input may be used to put all analog circuitry except

VREF into a low-current mode, saving power during inactive

periods. Recovery time from NAP mode is <30µs. It is available

only in the 14 pin DIP package.

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