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Hi Ruoxin,
Could this device input 36V sine wave? If not, can only 18 V sine wave be accepted?
PGA849 is unable to take 36V input voltage due to the input Vcm limitation. This is not RRIO Programmable instrumentation amplifier.
Depending on PGA849's supply rail configuration, it may take 18V sinusoidal input. It depends how the 18V input swing is defined. Is it 18Vrms, 18Vpk or 18Vpp input signal?
If the supply rails are +/-18Vdc, then PGA849 is unable to handle 18Vrms or 18Vpk input signal. 18Vpp means the input is 9Vpk, then it may work, if the Vcm is configured properly (Vcm is likely configured near 0Vdc or GND)
If 36V in single supply is configured, only 18Vpp input signal may work (same reasons provided above). However, the Vcm is likely configured close to the mid rail of 36Vdc.
I do not see the PGA849 instrumentation calculation yet, but the linear operating range may be fairly close to PGA855, see the application note below, download the PGA855 calculator.
If you have other questions, please let me know.
Best,
Raymond
Hi Ruoxin,
The input range of the PGA849 is a function of the input stage supplies, output stage supplies, selected gain and REF voltage, as well as the input common-mode voltage. We offer the PGA849 Input and Output Range Design Calculator tool to check the linear range of the device. This calculator will post on www.ti.com soon, since the device is still on preview. Nevertheless, the preliminary calculator and instructions are attached at the bottom of this post.
The PGA849 has fully-differential inputs, and the range is a function of the input common-mode voltage, where the input common-voltage is the average voltage of the PGA IN+ and IN- inputs.
- For example the device is powered with input stage supplies (VS+, VS-) of ±18V, output stage supplies (+LVDD, -LVSS) of ±18V, and REF voltage connected to GND, and PGA Gain =1V/V, the device can support a fully-differential input of ±17.5V maximum amplitude, while the input common-mode is centered at GND (see image below).
- Alternatively, in the same gain, reference and supply conditions, when the IN- input is connected to GND in single-ended input voltage fashion, the device can support a ±15.5V signal while powered with ±18V supplies at PGA Gain = 1V/V.
Attached is the PGA849 input and output range preliminary calculator. Also attached is a pdf file with instructions.
PGA849 Input and Output Range Preliminary Calculator:
PGA849-Input-and-Output-Range-Calc-prelim_8-16-24.xlsx
PGA849 Input and Output Range Calculator Instructions:
PGA849-Input-and-Output-Range-Calc-instructions.pdf
Thank you and Kind Regards,
Luis
