RM4301ASEA datasheet(5/19 Pages) SAMES

5 / 19 page

http://www.sames.co.za

5/19

PRELIMINARY

RM4301ASEA

SA4301A RELATED CIRCUITRY

All aspects discussed in this section are illustrated on the

complete meter schematic (Figure 7). The SA4301A

requires a split supply of +2.5V (VDD) and -2.5V (VSS)

around the meter ground node, which has to be connected

to the AGND pin of the SA4301A. These three supply lines

have to be properly decoupled using capacitors C10 and

C11 (220nF ceramic each) between the supplies and

ground and C12 (1μF ceramic) between the two supplies.

These capacitors are required to achieve good performance

and have to be placed as close to the device as possible.

Their placement is as important as their presence, placing

them more than a few millimeters away from the device

renders them useless. The on-chip reference current is

derived from a 47k

W resistor (R3) connected between VREF

and VSS. This resistor must be a 1% tolerance metal film

type or similar. The metal film ensures that less noise will be

induced into the device pin. This reference resistor should

be placed as close as possible to the device and C11.

The internal pulse dividers of the SA4301A are configured

through the pins RA, RB and FMS. These pins must either

be tied to VDD, VSS, PH/DIR or left floating. The FMS pin

cannot be tied to PH/DIR and will enable a fast pulse output

mode when left floating, which is typically not applicable to

an energy meter of this type. The setup pins should be

directly connected to VDD, VSS or PH/DIR, no pull-up or

pull-down resistors are required.

The stepper motor used to display the consumed energy

should be connected to the MOP and MON pins through two

small current limiting resistors (R8 and R9). For calibration

and performance verification purposes an LED and opto-

isolator are connected in series to the LED output pin of the

SA4301A. This output is active low so the LED and opto-

isolator are connected through a current limiting resistor to

VDD.

For more elaborate information on setting up and using the

SA4301A, refer to the SA4301A datasheet available on the

SAMES website at www.sames.co.za or from any SAMES

representative.

SETUP OF RA, RB AND FMS FOR RATED

CONDITIONS

The following equations and table state the basic pulse

constants and motor constants obtainable with the

SA4301A.

The pulse rate of the LED output for a balanced 3 phase

load is:

MAX

NOM

LED

1000

3600

LED

5000

IVP

p/kWh

(16)

where IVP is the input current to the SA4301A at VNOM and

assuming that the input current at IMAX on the current inputs

is 16µARMS. For VNOM = 220V the IVP input current should

typically be 11μA.

The motor output pulse rate is

p/kWh

LED

MOTOR

(17)

The variables DF_LED and DF_MO are defined by setting

FMS, RA and RB according to Table 2.

FMS

DF_LED

DF_MO

146

128

292

584

PH/DIR

1168

146

292

584

PH/DIR

1168

146

292

584

PH/DIR

1168

PH/DIR

146

PH/DIR

292

PH/DIR

584

PH/DIR

1168

976

1952

234

PH/DIR

468

392

784

234

PH/DIR

468

392

784

234

PH/DIR

468

PH/DIR

196

PH/DIR

392

PH/DIR

156

PH/DIR

312

Table 2: Division factors available on the SA4301A

‘0' indicates that the input is connected to VSS

'1' indicates that the input is connected to VDD

'Z' indicates that the input is left floating

'PH/DIR' indicates that the input is connected to PH/DIR

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