R

2

12 W

R

3

12 W

Device

Isolation

Barrier

C

2

(1)

330 pF

C

3

10 pF

(optional)

VDD1

VINP

VINN

GND1

VDD2

VOUTP

VOUTN

GND2

C

4

10 pF

(optional)

C

1

(1)

0.1 F

m

R

1

C

5

(1)

0.1 F

m

ADC

TMC320

C/F28xxx

C

14

13

11

9

1

2

3

4

R

R

R

SHUNT

Phase

AMC1200, AMC1200B

SBAS542D – APRIL 2011 – REVISED JULY 2015

www.ti.com

Typical Applications (continued)

8.2.1.1 Design Requirements

For better performance, the differential input signal is filtered using RC filters (components R2, R3, and C2).

Optionally, C3 and C4 can be used to reduce charge dumping from the inputs. In this case, take care when

choosing the quality of these capacitors; mismatch in values of these capacitors leads to a common mode error

at the modulator input. If implemented, TI recommends using NP0 capacitors for C2, C3 and C4.

Figure 33. Shunt-Based Current Sensing with the AMC1200

Similar to the current measurements, isolated voltage measurements can be performed as described in the .

8.2.1.2 Detailed Design Procedure

The floating ground reference (GND1) is derived from the end of the shunt resistor, which is connected to the

negative input of the AMC1200 (VINN). If a four-terminal shunt is used, the inputs of the AMC1200 are

connected to the inner leads and GND1 is connected to one of the outer shunt leads. The differential input of the

AMC1200 ensures accurate operation even in noisy environments.

TI recommends limiting the value of resistors R2 and R3 to less than 24 Ω to avoid the incomplete settling of the

AMC1200 input circuitry. The section provides more details on the AMC1200 input circuitry.

The differential output of the AMC1200 can either directly drive an analog-to-digital converter (ADC) input or can

be further filtered before being processed by the ADC. For more information on the general procedure to design

the filtering and driving stages for SAR ADCs, consult the TI Precision Designs 18 bit, 1Msps Data Acquisition

Block Optimized for Lowest Distortion and Noise (SLAU515), and 18 bit Data Acquisition Block Optimized for

Lowest Power (SLAU513) available for download at www.ti.com

16

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