TIDM-TIA: TIA

rockz

Part Number: TIDM-TIA
Other Parts Discussed in Thread: MSP430FR2355, TLV9062, TLV9042, TLV9002, TLV9001

Im building ambient light sensor with SFH2401 x 5 photo diodes (not an array). Can anyone suggest parts for the Transimpedance amplifier, ADC.

over 2 years ago

0 Leonardo Estevez over 2 years ago

TI__Genius 12615 points

Hi Viny,

The MSP430FR2355 has a dedicated TIA with 4 additional Smart Analog Combos which can be configured to operate in a TIA configuration.

https://www.ti.com/product/MSP430FR2355

The integrated 12 bit ADC supports multiple channels which can be connected to the output of each of the TIA and the four Smart Analog Combos.

BR,
Leo

0 rockz over 2 years ago in reply to Leonardo Estevez

Prodigy 90 points

Hi Leo,

Could you pls suggest discrete parts or solutions other than microcontroller.

0 Tim Claycomb over 2 years ago

TI__Genius 15410 points

Hi Viny,

Devices like the TLV9062, TLV9002, or TLV9042 work well in TIA applications. You typically want low input bias current to reduce errors. The devices I recommended are for low supply voltage (5V) and are CMOS devices which have low Ib. If you need a higher supply voltage, please let me know and I'll recommend some other devices.

Here is a document that may help in your design.

https://www.ti.com/lit/an/sboa220a/sboa220a.pdf

Thank you,

Tim Claycomb

0 rockz over 2 years ago in reply to Tim Claycomb

Prodigy 90 points

Hi Tim,

Thankyou for the document. How to decide on circuit bandwidth? i will be measuring visible light using the sensor, since it is continuous what could be the frequency to be used in calculation.

0 kai klaas69 over 2 years ago in reply to rockz

Guru 140200 points

Hi Viny,

you could use this circuit as a starting point:

viny_tlv9001.TSC

Kai

0 rockz over 2 years ago in reply to kai klaas69

Prodigy 90 points

Hi Kai,

Thankyou. I'ld like to know how you have considered the circuit bandwidth?

0 Tim Claycomb over 2 years ago in reply to rockz

TI__Genius 15410 points

Hi Viny,

Design Step 3 shows the equation to calculate the minimum bandwidth for the amplifier used as a TIA. Also TIPD176 shows a more in depth derivation of the equation.

The circuit bandwidth will be dependent on your system and is set by R3 and C2 in Kai's schematic. The frequency of the light you are measuring will determine the bandwidth of your circuit.

Thank you,

Tim Claycomb

+1 kai klaas69 over 2 years ago in reply to rockz

Guru 140200 points

Hi Viny,

the SFH2401 gives 76nA/lx. In order to measure day light with high lux a rather low R3 is chosen. About 4.9V / (10k x 76nA) = 6400lx can be measured with this circuit.

As the TLV9001 -like any other OPAmp- cannot go all the way down to 0V at the output, a bias of about 100mV {concretely 5V / (10k + 200) x 200 = 98mV} is provided by the help of R1 and R2.

The SHF2401 has a detector capacitance of 65pF. For stable operation a C2 of 100pF is chosen. See what happens when omitting C2. The small signal transient respsonse shows heavy ringing -or by other words- instability:

And the phase stability analysis shows a phase margin of only 20°:

viny_tlv9001_1.TSC

Kai

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TIDM-TIA: TIA