ISO224 datasheet(12/25 Pages) TI1

12 / 25 page

-10

-5

VIN (V)

VFSR

-15

VCMout

VCLIPPING

VOUTP

VOUTN

ISO224

SBAS738 – JUNE 2018

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8.3 Feature Description

8.3.1 Analog Input

The input stage of the ISO224 feeds a second-order, switched capacitor, feed-forward ΔΣ modulator. The

modulator converts the analog signal into a bitstream that is transferred over the isolation barrier, as described in

the section. The high-impedance and low bias-current input of the ISO224 makes the device suitable for isolated

voltage sensing applications.

Figure 5 visualizes the difference in the transfer function of the ISO224 depending on the input signal VIN, as

specified in the Recommended Operating Conditions table. With the input voltage within the specified full-scale

range VFSR, the output of the device changes in a linear way with small error as specified by the nonlinearity

parameter in the Electrical Characteristics table. If the input signal exceeds the VFSR range, the nonlinearity of

the output signals increases and the amplitude clips at VIN = VCLIPPING.

Figure 5. Transfer Function of the ISO224

There are two restrictions on the analog input signal at the IN pin. First, if the input voltage VIN exceeds the

range of –15 V to 15 V, the current must be limited to 10 mA to prevent damage to the input clamp, see the Input

Clamp Protection Circuit section for further information. In addition, the linearity and noise performance of the

ISO224 are ensured only when the analog input voltage remains within the specified linear full-scale range

(VFSR).

ISO224 Datasheet(PDF) 12 Page - Texas Instruments