TLV3011- Reference Pin

Matsumoto-san,

Often, comparators have a reference voltage applied to an input, to which the voltage on the other input is compared. That reference voltage is commonly developed by a resistive voltage divider connected to the V+ supply. The resistors values vary from one installation to the next, and they have a temperature coefficient that causes their value to change with temperature. Thus, the reference voltage may not be too exact. That may be okay if the application doesn't require high accuracy.

If high accuracy is required, then a higher performance voltage reference may be used; one that is compensated for temperature, supply voltage variations, load current, etc. Voltage references that provide high performance are usually available as standalone components, with standard voltages such as 1.242 V, 2.048 V, 2.5 V, 3 V, or other. A resistive divider can be placed at their output to attain a different voltage level if needed, and the regulation usually will be much better than that obtained from a power supply.

The references are usually a separate component which means an additional part must be used in the design and added to the PC board. The TLV3011 includes a high performance 1.242 V reference internal to the IC. Therefore, an external one isn't needed unless a higher voltage is desired.

The TVL3011 data sheet shows some examples of how the reference function can be used. It doesn't have to be used and can be left open in that case.

Regards, Thomas

PA - Linear Applications Engineering

Matsumoto-san,

The 1.24 V V_REF voltage is with respect to the V- pin voltage. Most often V- is 0 V because users tend to use a single supply with the TLV3011. However, sometimes users employ dual supplies in their system. For example, one could use +1.5 V/-1.5 V to power the TLV3011. In that case the 1.24 V V_REF voltage would be with respect to  -1.5 V (V-). If one measured the V_REF pin voltage with respect to ground (0 V), the voltage would measure about -0.26 V (-1.5 V + 1.24 V).

I hope that answers your question.

Regards, Thomas

PA - Linear Applications Engineering

Hi Nicolas,

By connecting the TLV3011 VREF pin to ground you would be shorting the reference output voltage pin to 0 V. That would be an unusual connection for the pin. The reference amplifier would go into current limit. What exactly that current level would be is not stated in the data sheet, but it may be milliamps, or tens of milliamps. The device would probably be okay, but you would be wasting a lot of current and heating the device unnecessarily.

Consider instead, the TLV3491. Although it has a push-pull output comparators with that type of output can often be used in applications where an open-drain comparator was used. The upper pull-up output transistor simply parallels the open-drain output pull-up resistor. Usually, it is only in wired-OR output configurations where the push-pull output substitution is a problem. The electrical characteristics are very similar between the TLV3011 and TLV3491.

Regards, Thomas

PA - Linear Applications Engineering