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PSoC™ 5, 3 & 1

New Contributor II

" CY8C5467LTI-LP003 " what is non buffered DAC in this chip?

in the datasheet of this CY8C5467LTI-LP003" chip datasheet , in page - 59 - Topic- 8.10.2 (Voltage DAC) it says that " For the voltage DAC (VDAC), the current DAC output is routed through resistors. The two ranges available for the VDAC are 0 to 1.02 V and 0 to 4.08 V. In voltage mode any load connected to the output of a DAC should be purely capacitive (the output of the VDAC is not buffered)." , so what is non-buffered output here? and what is the meaning of i can only connect capacitive loads only? , what i can do to use this dac as normal dac? do i have to connect any extra circuitry? if yes then please help me with the circuit diagram or any reference diagram so that i can understand the working and make my dac work like a normal one.

1 Solution
Honored Contributor II

Re: " CY8C5467LTI-LP003 " what is non buffered DAC in this chip?

JaVa,

PSoC doesn't have a voltage DAC, VDAC8 is emulated using current DAC, attached to a resistor (16k @ 4.08V range). Therefore output voltage of such DAC is V = I x R in the absence of any load. If load impedance is not infinity, then output of VDAC8 is V=  I x (R || Rload). For that reason datasheet requires load impedance 'purely capacitive', that is infinite resistance.

The rule of thumb is that any VDAC8 output going outside the chip must be buffered. When using PSoC built-in Opamps for buffering of the VDAC8 output, please note that the input impedance of the Opamp is not infinite (it is about 1M), which slightly affects the output voltage when VDAC8 range is 4.08V (R=16k).

/odissey1

2 Replies
Esteemed Contributor

Re: " CY8C5467LTI-LP003 " what is non buffered DAC in this chip?

Hi,

I think that it means that the output of VDAC is not capable to provide current.

So if you connect the output to a High-Z input, it should work.

But if you need get some current, you need to add a buffer to the output something like.

moto

Honored Contributor II