TC815 Datasheet, PDF(10/26 Page) Microchip Technology – 3-1/2 Digit Auto-Ranging A/D Converter with Triplex LCD Drive and Display Hold Function

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TC815 Datasheet, PDF (10/26 Pages) Microchip Technology – 3-1/2 Digit Auto-Ranging A/D Converter with Triplex LCD Drive and Display Hold Function

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TC815

3.5 Current Measurement

The TC815 measures current only under manual range

operation. The two user selectable full scale ranges

are: 20mA and 200mA. Select the current Measure-

ment mode by holding the I input (Pin 63) low at digital

ground potential. The OHM input (Pin 2) is left floating

or tied to the positive supply.

Two ranges are possible. The 20mA full scale range is

selected by connecting the 20mA input (Pin 3) to digital

ground. If left floating the 200mA full scale range is

selected.

External current to voltage conversion resistors are

used at the II input (Pin 45). For 20mA measurements

a 10â¦ resistor is used. The 200mA range needs a 1â¦

resistor; full scale is 200mV.

PC board trace resistance between analog common

and R16 (see Figure 2-1) must be minimized. In the

200mA range, for example, a 0.05 trace resistance will

cause a 5% current to voltage conversion error at II

(Pin 45).

The extended resolution measurement option operates

during current measurements. To minimize rollover

error the potential difference between ANALOG COM

(Pin 29) and system common must be minimized.

3.6 Measurement Options

(AC to DC Measurements)

In voltage and current measurements, the TC815 can

be configured for AC measurements. An on-chip oper-

ational amplifier and external rectifier components per-

form the AC to DC conversion.

When power is first applied, the TC815 enters the DC

Measurement mode. For AC measurements (current or

voltage), AC/DC (Pin 62) is momentarily brought low to

digital ground potential; the TC815 sets-up for AC mea-

surements and the AC liquid crystal display annuncia-

tor activates. Toggling AC/DC low again will return the

TC815 to DC operation.

If the Manual Operating mode has been selected, tog-

gling AC/DC will reset the TC815 back to the Auto-

Range mode. In Manual mode operation, AC or DC

operation should be selected first and then the desired

range selected.

The minimum AC voltage full scale voltage range is 2V.

The DC full scale minimum voltage is 200mV. AC cur-

rent measurements are available on the 20mA and

100mA full scale current ranges.

DS21474B-page 10

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