RS

OUT

LM94021

VDD

GND

CLOAD > 1100 pF

OPTIONAL

BYPASS

CAPACITANCE

OUT

LM94021

VDD

GND

OPTIONAL

BYPASS

CAPACITANCE

CLOAD < 1100 pF

LM94021

SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013

www.ti.com

Figure 14. LM94021 No Decoupling Required for Capacitive Loads Less than 1100 pF

Figure 15. LM94021 with Series Resistor for Capacitive Loading greater than 1100 pF

OUTPUT VOLTAGE SHIFT

The LM94021 is very linear over temperature and supply voltage range. Due to the intrinsic behavior of an

NMOS/PMOS rail-to-rail buffer, a slight shift in the output can occur when the supply voltage is ramped over the

operating range of the device. The location of the shift is determined by the relative levels of VDD and VOUT. The

shift typically occurs when VDD- VOUT = 1.0V.

This slight shift (a few millivolts) takes place over a wide change (approximately 200 mV) in VDD or VOUT. Since

the shift takes place over a wide temperature change of 5°C to 20°C, VOUT is always monotonic. The accuracy

specifications in the ELECTRICAL CHARACTERISTICS table already include this possible shift.

SELECTABLE GAIN FOR OPTIMIZATION AND IN SITU TESTING

The Gain Select digital inputs can be tied to the rails or can be driven from digital outputs such as microcontroller

GPIO pins. In low-supply voltage applications, the ability to reduce the gain to

−5.5 mV/°C allows the LM94021 to

operate over the full

−50°C to 150°C range. When a larger supply voltage is present, the gain can be increased

as high as

−13.6 mV/°C. The larger gain is optimal for reducing the effects of noise (for example, noise coupling

on the output line or quantization noise induced by an analog-to-digital converter which may be sampling the

LM94021 output).

Another application advantage of the digitally selectable gain is the ability to perform dynamic testing of the

LM94021 while it is running in a system. By toggling the logic levels of the gain select pins and monitoring the

resultant change in the output voltage level, the host system can verify the functionality of the LM94021.

14

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