7.3 Best Design Practices

Do not leave the analog inputs INP and INN of the AMC3301 unconnected (floating) when the device is powered

up. If the device inputs are left floating, the input bias current may drive the inputs to a positive value that

exceeds the operating common-mode input voltage and the output of the device is undetermined.

Connect the negative input (INN) to the high-side ground (HGND), either by a hard short or through a resistive

path. A DC current path between INN and HGND is required to define the input common-mode voltage. Take

care not to exceed the input common-mode range as specified in the Recommended Operating Conditions table.

For best accuracy, route the ground connection as a separate trace that connects directly to the shunt resistor

rather than shorting AGND to INN directly at the input to the device. See the Layout section for more details.

The high-side LDO can source a limited amount of current (IH) to power external circuitry. Take care not to

overload the high-side LDO.

The low-side LDO does not output a constant voltage and is not intended for powering any external circuitry. Do

not connect any external load to the LDO_OUT pin.

7.4 Power Supply Recommendations

The AMC3301 is powered from the low-side power supply (VDD) with a nominal value of 3.3 V or 5 V. TI

recommends a low-ESR decoupling capacitor of 1 nF (C8 in Figure 7-5) placed as close as possible to the VDD

pin, followed by a 1-µF capacitor (C9) to filter this power-supply path.

The low-side of the DC/DC converter is decoupled with a low-ESR 100-nF capacitor (C4) positioned close to

the device between the DCDC_IN and DCDC_GND pins. Use a 1-µF capacitor (C2) to decouple the high side

in addition to a low-ESR, 1-nF capacitor (C3) placed as close as possible to the device and connected to the

DCDC_OUT and DCDC_HGND pins.

For the high-side LDO, use low-ESR capacitors of 1 nF (C6), placed as close as possible to the AMC3301,

followed by a 100-nF decoupling capacitor (C5).

The ground reference for the high-side (HGND) is derived from the terminal of the shunt resistor which is

connected to the negative input (INN) of the device. For best DC accuracy, use a separate trace to make this

connection instead of shorting HGND to INN directly at the device input. The high-side DC/DC ground terminal

(DCDC_HGND) is shorted to HGND directly at the device pins.

C2 1 µF

C6 1 nF

C5 100 nF

C3 1 nF

C1 100 nF

R2 10

R4 10

C10 10 nF

I

FB1

FB2

FB3

DCDC_OUT

DCDC_HGND

HLDO_IN

HLDO_OUT

HGND

INP

INN

NC

AMC3301

C9

1 µF

C8

1 nF

C4

100 nF

R1

47 k

DCDC_IN

LDO_OUT

VDD

OUTP

OUTN

GND

DIAG

DCDC_GND

3.3 V / 5 V supply

to uC (optional)

to RC filter / ADC

to RC filter / ADC

Figure 7-5. Decoupling the AMC3301

Capacitors must provide adequate effective capacitance under the applicable DC bias conditions they

experience in the application. Multilayer ceramic capacitors (MLCC) typically exhibit only a fraction of their

nominal capacitance under real-world conditions and this factor must be taken into consideration when selecting

these capacitors. This problem is especially acute in low-profile capacitors, in which the dielectric field strength is

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AMC3301

SBAS917C – AUGUST 2019 – REVISED MAY 2025

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