ES636 データシートの表示（PDF） - Cyrustek corporation

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ES636

True RMS-to-DC Converters

Cyrustek corporation 

ES636

True RMS-to-DC Converters

Electrical Characteristics-ES636(continued)

(TA= +25℃, Vs = +3V, -Vs = -3V, unless otherwise noted.)

Power SUPPLY

Rated Performance

Dual Supplies

Single Supply

Quiescent Current (Note 6)

+3/-3

V

+2/-2.5

±10

V

+5

+20

V

0.8

1

mA

Note 1: Accuracy is specified for 0 to 400mV, 1kHz sine-wave input. Accuracy is degraded at higher RMS signal levels.

Note 2: Measured at pin 8 (IOUT), with pin 9 tied to COMMON.

Note 3: Error vs. crest factor is specified as an additional error for 200mVRMS rectangular pulse input, pulse width = 200μs.

Note 4: Input voltages are expressed in volts RMS.

Note 5: With 10 kΩ external pull-down resistor from pin 6 (BUF OUT) to – Vs.

Note 6: With BUF input tied to COMMON.

Detailed Description

Figure 1 shows the simplified schematic of ES636. It consists of four major subcircuits:

absolute value circuit (rectifier), square/divider, current mirror and buffer amplifier. The

actual computation performed by the ES636 follows the equation:

VRMS = Avg. [VIN2／VRMS]

The input voltage, VIN, applied to the ES636 is converted to a unipolar current I1

(Figure 1) by the absolute-value/voltage. This current drives one input of the

squarer/divider that produces a current I4 , which has the transfer function:

Ι4

=

Ι12

Ι3

The current I4 drives the internal current mirror through a low-pass filter formed by R1

and the external capacitor, CAV. As long as the time constant of this filter is greater than

the longest period of the input signal, I4 is averaged. The current mirror returns a

current, I3, to the square/divider to complete the circuit. The current I4 is then a function

of the average of (I12/ I4), which is equal to I1RMS.

The current mirror also produces a 2．I4 output current, IOUT, that can be used directly

or converted to a voltage using resistor R2 and the internal buffer to provide a

low-impedance voltage output. The transfer function for the ES636 is:

VOUT=2．R2．IRMS= VIN

6

09/02/16

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