FX621 查看數據表（PDF） - CML Microsystems Plc

零件编号

产品描述 (功能)

比赛名单

FX621

Low-Power Subscriber Private Metering (SPM) Detector

CML Microsystems Plc 

Application Information

The notes on these pages are intended to assist in calculating the external components required to operate the FX621 as an

SPM Detector.

FX621P

DETECTOR INPUT PIN No.

3

C9

R7

INSET

VBIAS

C1

V BIAS

D1

D2

R1

C2

R2

R3

C7

D3

D4

V BIAS

VDD

X1

XTAL/CLOCK

XTAL

R5

R6

1

V DD

2

16

SYSTEM SELECT

15

DETECTOR INPUT 3

OUTPUT

14

AMP INPUT (+)

MODE SELECT

4 FX621P 13

AMP INPUT (-)

5

OUTPUT RESET

12

C6

AMP OUTPUT 6

PULSE LENGTH

11

x

7

SPACE LENGTH

10

V SS

8

9

V BIAS

R4

C8

C3

C4

C5

V SS

(a) Differential Input Configuration

Component References

Component

Reference

Component

R1

Note 4

C1

R2

Note 4

C2

R3

390kΩ ± 1.0%

C3

R4

390kΩ ± 1.0%

C4

R5

Note 5

C5

R6

Note 5

C6

R7

1.0MΩ

C7

D1 to D4 1N4148 or equivalent

C8

(small signal type)

C9

X1

4.433619MHz

Reference

Note 4

Note 4

1.0µF ± 20%

Note 5

Note 5

1.0µF ± 20%

12.0pF ± 10.0%

12.0pF ± 10.0%

0.1µF ± 10.0%

Fig.2 Recommended External Components

V BIAS

C7

D1

C2

R2

D3

V BIAS

R3

5

4+

"SYSTEM GAIN

SET" AMPLIFIER

6

3

AMP

DETECTOR

OUTPUT INPUT

C3

V SS

(b) Single Input Configuration

Gain Component Calculations

(1)

Calculate the FX621 sensitivity.

Device Sensitivity – at the Detector Input (Figure 1) is

dependent upon the V value and is calculated as:

DD

Device Sensitivity

≈

0.2 x V

DD

2 x √2

(Vrms)

(2)

Ascertain the required National {Minimum Will-

Decode} and [Maximum Will-Not Decode] Levels.

(3)

Calculate the acceptable range of required Gain/

Attenuation for the levels in Note 2, using the “System Gain Set”

amplifier.

The gain requirement is calculated as :

[Max] / {Min} Gain

[or]

=

Device Sensitivity

{ Minimum Will-Decode Level }

[ Maximum Will-Not Decode Level ]

Choose a gain figure that meets both level requirements.

(4)

Calculate the gain/attenuation components for the

chosen gain.

Gain Components – for a differential input:

R1 = R2

R =R

3

4

C8 = C7

C =C

1

2

Gain =

ZFeedback

Z

Input

(R4 //X(C8))

(R + X(C ))

1

1

This calculation approximates as:

R

1

≈

R

4

1.2 x (selected gain)

and

C1 ≈

1

2π

x

R

1

x

6.0kHz

– using the nearest preferred value components.

The values of R and C have been calculated to give a high-

1

1

pass cut-off between the audio and SPM tone frequencies,

approximately 6kHz. C7 and C8 are anti-alias components and

are calculated for an approximate cut-off frequency of 32kHz.

3

Share Link: