SSM2166 maximum input voltage

Hi, sshetty640!

In section "APPLICATIONS INFORMATION" of the datasheet says that "The device operates on a single 5 V supply, accepts input signals up to 1 V rms, and produces output signal levels >1 V rms (3 V p-p) into loads >5 kΩ". I.e. device support AC signal only, using of decoupling capacitor is necessarily

Thank you KirV,

I have three following concerns.

1. We are interfacing ±15V system to SSM2166(0-5V range). We are designing input protection circuit for SSM2166 using schottky diode. So it is required to know what maximum negative voltage can be applied with decoupling capacitor?

2. We need rotation point at 26mV. We tried increasing resistor value but not able make it below 28mV.

3. If we provide external bias of more than 1.5V(say 2V) at AUD-IN pin, will the IC working dynamic range(voltage) increase(more than 1Vrms)? any damage to IC will happen?

Waiting for reply!!!!

About protection: in datasheet says that 1V it is input signal causing 1% THD however absolute maximum of input signal equal supply voltage. In my opinion, this means peak voltage, therefore maximum input range is +/-5V (or 3.54Vrms). Microphone can't create such a signal for this reason in datasheet not says about this case. This is my opinion only

Can you attach image of protection circuit?

D542 and D543 is used for input protection. Since these diode have Vf of 0.3V , at Audio+In pin max signal range would be 5.3V and -0.3V in case of any voltage spike.

Please let me know if these voltage would affect the IC? Any input protection is provided inside the IC?

Hi, sshetty640

Probability of input stage damage at this input voltage is extremely low. The IC can have bipolar or FET input stage. Both type transistors can be represented as two p-n junction and input voltage equal supply +/- 300 mV can not cause forward biasing of this diodes and increasing current up to damaging.

I hope that's what you're asking.

Hi Sshetty,

First SSM2166 has a internal protection diode in its input.

Basing on your schematic below, seem you have everything you need for the circuit, populate R583 and R587 to create an attenuation of not more than 1/6 (I am seeing R587 as DNP, populate this). this attenuator will "scale down" your input while maintaining the fidelity of the signal. May I know the reason why you need to put external bias to the device? SSM2166 is internally biased as based on figure 16, and it is expected to be in the level of Vcc/2, this is done to maximize the dynamic range of the device. adding a bias voltage higher and lower than that on the internally set bias could induce current flow to the input which will become harmful to the device.

If you look at table 2. max input is dictated by the supply. hence the part can still handle input > 1Vrms but not more than the supply. However, please be noted that THD will increase as the input becomes higher. one way to go around this is to further decrease your attenuation possibly 1/10 of the input signal, but by doing so this will increase the minimum voltage that the SSM2166 process. Ultimately you should identify what is the maximum and minimum signal amplitude that you want your system to accept, and with this information set the attenuation factor accordingly.

Regards,

Joven

Hi, Joven

Jvillanu said:

SSM2166 is internally biased as based on figure 16, and it is expected to be in the level of Vcc/2

In datasheet says: "A dc voltage of approximately 1.5 V is present at AUDIO +IN (Pin 7)", but this value not equal Vcc/2

Regards,

Kirill