09/02/16

11

ES636

True RMS-to-DC Converters

reduce the settling time and ripple is to use a post filter.

Two suggested circuits are

west frequency of interest. And the output ripple will be removed by the post filter.

level. Figure 11

present the frequency response of the converters from 35mV to 1V for ES636.

, and ±3dB of reading

dditional error. Caution must be used when designing RMS measuring systems so that

sho

th

lo

Figure 5(a). ES636 with a One-Pole Filter

(b) with a Two-Pole Filter

Decibel Output (dB)

The dB output of the ES636 originates in the squarer/divider section and works well

over a 50dB range. The dB output has a temperature drift of 0.03dB/℃.

Frequency Response

ES636 utilizes a logarithmic circuit in performing the RMS computation of the input

signal. The bandwidth of the RMS converters is proportional to signal

re

The dashed lines indicate the upper frequency limits for 1%, 10%

a

CURRENT

MIRROR

SQUARE

DIVIDER

ABSOLUTE

VALUE

Cav

-

+

-Vs

+Vs

Vin

Vout

BUF

+

-

1

2

3

4

5

6

78

9

10

11

12

13

14

+Vs

C

2

+

-

CURRENT

MIRROR

SQUARE

DIVIDER

ABSOLUTE

VALUE

Cav

-

+

-Vs

+Vs

Vin

BUF

+

-

1

2

3

4

5

6

78

9

10

11

12

13

14

+Vs

Vout

C

2

C

3

10K

Ω

-

+