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sames

SA2002D

http://www.sames.co.za

The current and voltage sense inputs are both identical. Both

inputs are differential current driven up to ±25µA peak. One

input of the voltage sense amplifier is internally connected to

GND. This is possible because the voltage sense input is much

less sensitive to externally induced parasitic signals compared

to the current sense inputs.

ELECTROSTATIC DISCHARGE (ESD)

PROTECTION

POWER CONSUMPTION

VREF

Current sense input (IIP and IIN)

Voltage Sense Input (IVP)

The SA2002D integrated circuit's inputs/outputs are protected

against ESD.

The power consumption rating of the SA2002D integrated

circuit is less than 25mW.

A bias resistor of 24k

sets optimum bias and reference

conditions on chip. Calibration of the SA2002D should be done

on the voltage input as described in Typical Applications.

Figure 3 on page 4 shows the typical connections for the

current sensor input. The resistor R1 and R2 define the current

level into the current sense inputs of the SA2002D. At

maximum rated current the resistor values should be selected

for input currents of 16µA

.

The values for resistors R1 and R2 can be calculated as

follows:

R1 = R2 = (I /16µA) x RSH/2

Where I

=

Line current

RSH

=

Shunt resistor or termination

Resistor if a CT is used as the current sensor.

The value of RSH, if used as the CT's termination resistor,

should be less than the DC resistance of the CT's secondary

winding. The voltage drop across RSH should not be less than

16mV

at rated currents.

The current into the A/D converter should be set at 14µA

at

nominal mains voltage. The voltage sense input saturates at

an input current of ±25µA peak. Referring to Figure 3 the

typical connections for the voltage sense input is illustrated.

Resistors R3, R4 and R5 set the current for the voltage sense

input. The mains voltage is divided down to 14V

. The current

into the A/D converter input is set at 14µA

via resistor R5.

INPUT SIGNALS

W

RMS

L

L

RMS

RMS

RMS

RMS

Rated condition select (R0, R1, R2)

The rated condition select pins R0, R1 and R2 are inputs,

which configure the SA2002D for different rated conditions.

This feature eliminates the need for different stepper motor

gear ratios. The LED pulse output follows the average power

consumption measured.

*This figure not in parenthesis indicates that a MOP pulse

followed by a MON pulse is treated as one energy pulse. The

figure inside parenthesis means that a MOP pulse followed by

a MON pulse is treated as two energy pulses.

The Motor pulse rate is not restricted to 100 (200) pulses/kWh.

The following examples show how different LED and motor

pulse rates can be achieved:

Example 1. A manufacturer designing a 220V/10A meter can

choose to have the pins R2, R1 and R0 connected as for a

220V/20A (R2=0, R1=0 and R0=1). In comparison to table 1

the Rated Condition is now half (2200W), this in turn doubles

the LED and Motor Pulse output rates as shown in the

following table:

0

0

0

0

1

1

1

1

0

0

1

1

0

0

1

1

0

1

0

1

0

1

0

1

220V/10A

220V/20A

220V/40A

220V/80A

220V/6A

220V/30A

220V/60A

Test Mode

6400

3200

1600

800

6400

3200

1600

Test Mode

100 (200)

100 (200)

100 (200)

100 (200)

100 (200)

100 (200)

100 (200)

-

R2 R1 R0

Rated

Condition

LED Output

(Pulses/

KWh)

Motor Pulse

Rate (Pulses/

KWh)*

Table 1

0

0

1

220V/10A

6400

100 (200)

R2 R1 R0

Rated

Condition

LED Output

(Pulses/

KWh)

Motor Pulse

Rate (Pulses/

KWh)*

Example 2. A manufacturer designing a 220V/80A meter can

choose to have the pins R2, R1 and R0 connected as for a

220V/40A (R2=0, R1=0 and R0=1). In comparison to table 1

the Rated Condition has doubled (17600W), this in turn halves

the LED and Motor Pulse output rates as shown in the

following table:

0

1

0

220V/80A

800

50 (100)

R2 R1 R0

Rated

Condition

LED Output

(Pulses/

KWh)

Motor Pulse

Rate (Pulses/

KWh)*