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SA9122EFA

SINGLE PHASE UNIDIRECTIONAL POWER/ENERGY METERING IC WITH SEPERATE 64 SEGMENT LCD DRIVER

South African Micro Electronic Systems 

SA9122E

1. Power calculation

In the Application Circuit (Figure 1), the voltage drop across the shunt will be

between 0 and 16mV (0 to 80A through a shunt resistor of 200µΩ). This voltage is

converted to a current of between 0 and 16µA, by means of resistors R1 and R2.

The current sense input saturates at an input current of ±25µA peak.

For the voltage sensor input, the mains voltage (230VAC) is divided down through

a divider to 14V. The current into the A/D converter input is set at 14µARMS at nominal

mains voltage, via resistor R4 (1MΩ).

In this configuration, with a mains voltage of 230V and a current of 80A, the output

frequency of the SA9122E power meter chip at FOUT1 is 1.16kHz. In this case, 1

pulse will correspond to an energy consumption of 18.4kW/1160Hz = 15.9Ws.

The output frequency at FOUT2 is FOUT1 /290 (i.e. The frequency ouput at FOUT1

divided by 290).

2. Analog Input configuration

The input circuitry of the current and voltage sensor inputs are illustrated below.

These inputs are protected against electrostatic discharge through clamping

diodes.

The feedback loops from the outputs of the amplifiers AI and AV generate virtual

shorts on the signal inputs. Exact duplications of the input currents are generated

for the analog signal processing circuitry.

V DD

IIN

CURRENT

V SS

SENSOR

AI

INPUTS

V DD

IIP

V SS

VDD

IVN

VOLTAGE

SENSOR

V SS

INPUT

AV

6/12

DR-00935

GND

sames

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