SA9602M
TYPICAL APPLICATIONS
In the Application Circuits (Figures 1 and 2), the components required for power metering
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 SA9602M integrated circuit are:
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 16µARMS into the SA9602M at
maximum line current.
Values for RSH of less than 200µΩ should be avoided.
R1 = R2 = (IL/16µARMS) * RSH/2
Where IL
RSH
=
=
Line current
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 14µARMS
.
R7 defines all on-chip bias and reference currents. With R7 = 24kΩ, optimum conditions
are set. R7 may be varied within ±10% for calibration purposes. Any change to R7 will
affect the output quadratically (i.e.: R7 = +5%, fP = +10%).
The formula for calculating the output frequency is given below:
FOSC
II .IV
fLED= 11.16
FOUTX
*
*
*
2
3.58MHz
IR
Where FOUTX = Frequency for selected rated condition
FOSC
= Oscillator frequency (2MHz ...... 4MHz)
II
= Input current for current input (16µARMS at rated)
= Input current for voltage input (14µARMS at rated)
IV
IR
= Reference current
(typically 50µA)
XTAL is a colour burst TV crystal (f = 3.5795 MHz) for the oscillator. The oscillator
frequency is divided down to 1.7897 MHz on-chip, to supply the digital circuitry and the
A/D converters.
11/16
sames
SAMES [ SAMES ]
