7.3.2 Isolation Channel Signal Transmission

As shown in Figure 7-1, the AMC0x11R uses an on-off keying (OOK) modulation scheme to transmit the

modulator output bitstream across the SiO2-based isolation barrier. The transmit driver (TX) is illustrated in the

Functional Block Diagram . TX transmits an internally generated, high-frequency carrier across the isolation

barrier to represent a digital one. However, TX does not send a signal to represent a digital zero. The nominal

frequency of the carrier used inside the AMC0x11R is 480MHz.

The receiver (RX) on the other side of the isolation barrier recovers and demodulates the signal and provides

the input to the analog filter. The AMC0x11R transmission channel is optimized to achieve the highest level of

common-mode transient immunity (CMTI) and the lowest level of radiated emissions. The high-frequency carrier

and RX/TX buffer switching cause these emissions.

Modulator Bitstream

on High-side

Internal Clock

Signal Across Isolation Barrier

Recovered Sigal

on Low-side

Figure 7-1. OOK-Based Modulation Scheme

7.3.3 Analog Output

The AMC0x11R provides a single-ended analog output voltage proportional to the input voltage. The output is

referred to GND2 and is galvanically isolated from the input of the device. The output is designed to connect

directly to the input of an ADC.

The full-scale output voltage is set by the REFIN pin. For any input voltage within the specified linear input

range, the device outputs a voltage equal to:

VOUT = VIN / VClipping x VREFIN = (VINP – VSNSN) / VClipping x VREFIN

(1)

Connect REFIN to the same reference voltage as the ADC to match the ADC dynamic input voltage range. With

a shared reference voltage, the ADC outputs a positive full-scale code when the clipping voltage is applied to

the input of the AMC0x11R. The output buffer requires a minimum headroom of 250mV against GND2 for linear

operation. Therefore, the device shows non-linear behavior for input voltages near 0V.

Calculate the minimum input voltage for linear operation as follows:

VINP, MIN = (250mV x VClipping) / VREFIN

(2)

For example, the minimum linear input voltage for the AMC0x11R device with a clipping voltage of 2.56V and

VREFIN = 5V, is 128mV.

The device is linear within the specified linear full-scale range. Beyond the linear full-scale range, the output

continues to follow the input, but with reduced linearity performance. The output clips when the input voltage

reaches the clipping voltage. Figure 7-2 shows the input-to-output transfer characteristic.

AMC0211R, AMC0311R

SBASAR1 – JULY 2025

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