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SA9106APA

SINGLE PHASE WATT MEASUREMENT IC WITH INTEGRATED 5 DIGIT LED DISPLAY DRIVER

South African Micro Electronic Systems 

SA9106A

4. Electrostatic Discharge (ESD) Protection

The SA9106A integrated circuit inputs/outputs are protected against ESD according

to Mil-Std 883C, method 3015.

5. Power Consumption

The power consumption rating of the SA9106A integrated circuit is less than 50mW,

excluding the display.

TYPICAL APPLICATIONS

In the Application Circuits (Figures 1 and 2) the components required for power

measurement applications, are shown.

In Figure 1 a shunt resistor is used for current sensing. In this application, the circuitry

requires a +2.5V, 0V, -2.5V DC supply.

In the case of Figure 2, when using a current transformer for current sensing, a +5V, 0V

DC supply is sufficient.

The most important external components for the SA9106A integrated circuit are:

C1 and C2 are the outer loop capacitors for the two integrated oversampling A/D

converters. The value of these capacitors is 560pF.

The actual values determine the signal to noise and stability performance. The tolerances

should be within ±10%.

C3 and C4 are the inner loop capacitors of the A/D converters. The optimum value is

3.3nF. The actual values are uncritical. Values smaller than 0.5nF and larger than 5nF

should be avoided.

R2, R1 and RSH are the resistors defining the current level into the current sense input.

The values should be selected for an input current of 16µA into the SA9106A at maximum

line current.

Values for RSH of less than 200µΩ should be avoided.

R1 = R2 = (IL/16µA) * RSH/2

Where I

L

= Line current

RSH = Shunt resistor/termination resistor

R3, R6 and R4 set the current for the voltage sense input. The values should be selected

so that the input current into the voltage sense input (virtual ground) is set to 14µA.

R7 together with the trimpot RT defines all on-chip bias and reference currents. The bias

resistor value (RB = R7 + RT) may be varied within ±10% for calibration purposes. Any

change to RBwill affect the displayed value quadratically (i.e.: RB = +5%, Display value

= +10%).

XTAL is a colour burst TV crystal (f = 3.5795MHz) for the oscillator. The oscillator

frequency is divided down to 1.7897MHz on-chip to supply the digital circuitry and the

A/D converters.

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