SA9109B Ver la hoja de datos (PDF) - South African Micro Electronic Systems

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SA9109B

MONOCHIP SINGLE PHASE BIDIRECTIONAL KILOWATT HOUR METERING IC

South African Micro Electronic Systems 

SA9109B

The kWh values of the LCD display digits, are given in the table below. The

resolution of the Least Significant Digit is normally programmed to 0.1kWh:

105 104 103 102 101 100 10-1 kWh

4. Device Programming

The SA9109B contains on-chip registers which enables the meter manufacturer to

store various data:

Slope Adjustment

The slope of the device may be adjusted by programming a slope constant (KS) into

the device during calibration. The output frequency at SDO (fP) is calculated by

means of the following formula:

FOSC

I .I 40062.5

fP = 11.16

* 3.5795MHz *

I V*

IR2

KS

Where

FOSC = Oscillator frequency (2MHz ...... 4MHz)

II

= Input current for current sensor input (16µA at rated line current)

IV

= Input current for voltage sensor input (14µA at rated line voltage)

I

= Reference current (typically 50µA)

R

KS

= Slope constant (1025 ... 16384))

(The default value is 11389)

By changing the slope of the device the resolution of the LCD, together with the

pulse rate on SDO may be changed by up to an order. The block diagram below

illustrates the display update rate.

Programmable slope divider

40062.5*

P ulses / s

1/K s

1 / 64

D isplay

Incr em ent

D R -0 1 2 56

fp

* At rated conditions

The display is incremented after every 64th pulse on SDO.

sames

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