6.3.4 Isolated DC/DC Converter

The AMC3301 offers a fully integrated isolated DC/DC converter that includes the following components as

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 converter. This circuit does not output a constant voltage and is not intended for driving any external load.

• 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 high-side LDO outputs a constant voltage and can provide a limited amount of current to

power external circuitry.

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

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

minimize the 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 AMC3301 and can

source up to IH of additional DC current for an optional auxiliary circuit such as an active filter, preamplifier, or

comparator. IH is specified in the Electrical Characteristics table as a DC, non-switching current.

6.3.5 Diagnostic Output

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

As shown in Figure 6-3, during power-up, the DIAG pin is actively held low until the high-side supply is in

regulation and the device operates properly. During normal operation, the DIAG pin is in high-impedance (Hi-Z)

state and is pulled high through an external pullup resistor. 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). In this case, the amplifier outputs are driven to the VFAILSAFE value that is shown in Figure 6-2.

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

below their respective undervoltage detection thresholds (brown-out). In this case, the low-side may still

receive data from the high-side but the data may not be valid. The amplifier outputs are driven to the

VFAILSAFE value that is shown in Figure 6-2.

High-side supply undervoltage

DIAG

Power-up

Normal

Operation

Normal

Operation

Figure 6-3. DIAG Output Under Different Operating Conditions

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

leave open if not used.

6.4 Device Functional Modes

The AMC3301 is operational when the power supply VDD is applied, as specified in the Recommended

Operating Conditions table.

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AMC3301

SBAS917C – AUGUST 2019 – REVISED MAY 2025

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