7.3.4 Isolated DC/DC Converter

The AMC3311 offers a fully integrated isolated DC/DC converter that includes the following components

illustrated in the Functional Block Diagram:

• Low-dropout regulator (LDO) on the low-side to stabilize the supply voltage VDD that drives the low-side of

the DC/DC converter

• Low-side full-bridge inverter and drivers

• Laminate-based, air-core transformer for high immunity to magnetic fields

• High-side full-bridge rectifier

• High-side LDO to stabilize the output voltage of the DC/DC converter for high analog performance of the

signal path

The DC/DC converter uses a spread-spectrum clock generation technique to reduce the spectral density of

the electromagnetic radiation. The resonator frequency is synchronous to the operation of the ΔΣ modulator to

minimize interference with data transmission and support the high analog performance of the device.

The architecture of the DC/DC converter is optimized to drive the high-side circuitry of the AMC3311 and can

source up to IH, as specified in the Electrical Characteristics table, of additional current for an optional auxiliary

circuit such as an active filter, preamplifier, or a high-speed isolated comparator such as an AMC23C11.

7.3.5 Diagnostic Output and Fail-Safe Behavior

The open-drain DIAG pin can be monitored to confirm the device is operational and the output voltage is valid.

During power-up, the DIAG pin is actively held low until the high-side supply is in regulation and the device

operates properly. The DIAG pin is actively pulled low if:

• The low-side does not receive data from the high-side (for example, because of a loss of power on the

high-side). The amplifier outputs are driven to negative full-scale.

• The high-side DC/DC output voltage (DCDC_OUT) or the high-side LDO output voltage (HLDO_OUT) drop

below the respective undervoltage detection thresholds VDCDCUV and VHLDOUV, as specified in the Electrical

Characteristics table. In this case, the low-side can still receive data from the high-side but the data can

possibly be invalid. The amplifier outputs are driven to negative full-scale.

During normal operation, the DIAG pin is in a high-impedance state. Connect the DIAG pin to a pullup supply

through a resistor or leave open if not used.

7.4 Device Functional Modes

The AMC3311 is operational when the power supply VDD is applied, as specified in the Recommended

Operating Conditions table.

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AMC3311

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