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# [FAQ] TPL1401: How to generate a DC setpoint or bias using the TPL1401?

Part Number: TPL1401
Other Parts Discussed in Thread: TINA-TI

I am wanting to know how to use the TPL1401 to generate a DC bias or DC setpoint.

• The TPL1401 can generate a DC bias or setpoint with integrated reference and load regulation, and 8-bit programmability.

Simple circuits to achieve a DC bias, like resistor dividers, have no load regulation and no programmability. LASER trimmed dividers provide higher precision, and a small level of programmability, but they still lack load regulation.

In the simple circuits mentioned above, the voltage output of the resistor divider will be skewed with an increasing current load. This TINA-TI simulation shows the output current and voltage vs the load resistance. As the resistance approaches infinity, the output voltage approaches the ideal voltage output value of 2.5V.

It’s possible to add an output buffer to the resistor divider as seen here:

The output voltage remains at the constant 2.5V, even as the load decreases and the current drawn by the load increases.

The example circuit below provides simple, integrated DC biasing solution using the TPL1401. The integrated buffer provides the load regulation as discussed above, as well as an internal precision reference, and the ability to program different DC biases without making any circuit modifications. The desired DC bias can be programmed into the TPL1401’s nonvolatile memory, NVM, so that even after a power cycle, the DC bias is set just like the traditional resistor divider circuits.

Below are instructions to save the DC bias in the NVM.

By default, the TPL1401 output powers on to high impedance. To start the TPL1401 at mid code, write the desired code to bits 11:2 of the DPOT_POSITION register. The code can be calculated using:

Then, to save this value in the NVM, write a 1 to the NVM_PROG bit, bit 4, of the PROTECT register. The next time the TPL1401 is power cycled, the output will default to the saved value.

(Register tables taken from the TPL1401 datasheet version * Sept 2020)

The TPL1401 can be found in many common applications:

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