CS5462 datasheet(13/18 Pages) CIRRUS

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CS5462

4.2.2

Mechanical Counter Format

In mechanical counter mode, the CS5462 produc-

es pulses on E1 and E2 which can be used to drive

a bi-directional mechanical counter. Each pin pro-

duces active-low pulses which have pulse widths

of 125 ms or 15 ms, depending on the frequency

selected. In the figure below, the frequency and

corresponding pulse width is shown for each op-

tion available. In this mode when energy is posi-

tive, the pulses appear on E1; when energy is

negative, pulses appear on E2.

4.3

Energy Direction Indicator

For either pulse output mode, the NEG pin can be

used to indicate the direction of the energy calcu-

lated. The NEG pin is updated at the sample rate

of the converter. If negative energy is detected the

NEG pin will become active low and will remain ac-

tive low until positive energy is detected.

4.4

Internal Calibration Option

For most power meter applications the standard

accuracy requirements require the meter be cali-

brated to within a certain percentage. Calibrating a

CS5462 meter can be done a number of ways.

One calibration method is to externally adjust the

front-end input circuit by using a potentiometer or

resistor network. By adjusting the amount of gain in

the resistor divider on the front end the energy out-

puts can be adjusted to fit the accuracy required.

Although this method is available, it may be costly

to add the additional components and the accuracy

required is often difficult to achieve. As an alterna-

tive the CS5462 is designed to allow the user to

calibrate the part without the need for external po-

tentiometers or resistor networks. The CS5462

provides a digital on-chip calibration solution. This

digital alternative can calibrate energy registration

error to within 0.1% without any analog adjust-

ments.

This calibration is accomplished by connecting

each Configuration Input pin, CAL1 and CAL0, to

one of the Program Select Output pins, P1 - P7. At

startup the CS5462 will scan the CAL1 and CAL0

pins to discern what connections are made, and

then calibrate the gain accordingly.

CAL1 and CAL0 each have seven options which

allows for 49 different steps of 0.2% between

+4.8% and -4.8% of expected energy output. Be-

fore startup, CAL1 and CAL0 must each be con-

nected to only one of the program select pins.

To Calibrate the CS5462:

1. Connect CAL1 and CAL0 to P4. This connection

will adjust the energy outputs by 0%.

2. Apply known current and voltage signals to the

inputs of the CS5462.

3. Measure the average pulse output frequency of

FOUT, E1, or E2.

4. The average frequency will be within some per-

centage of the expected frequency. Depending on

the output of the uncalibrated chip, the CAL0 and

CAL1 pins can be adjusted using the above options

(see “User Defined Settings” on page 14 for more

on calibration).

4.5

Power-on Reset

The CS5462 is equipped with internal circuitry that

will put the chip into reset if power supply is lost.

This is particularly useful in black-out or brown-out

situations in which the power supply temporarily in-

terrupted. The CS5462 will enter into reset if the

power drops below 2.5 V. The chip will remain in

reset until the supply rises to 4 V (See Figure 6) at

pulse width

Positive Energy

Negative Energy

2 Hz

16 Hz

125 ms

15 ms

Pulse Width

Frequency

FREQ

connected to:

CAL 1

+4.2%

+2.8%

-2 .8 %

-4 .2 %

CAL 0

+0.6%

+0.4%

-0 .4 %

-0 .6 %

+1.4%

-1 .4 %

+0.2%

-0 .2 %

Figure 6. Calibration Options

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