TCS3200, TCS3210

PROGRAMMABLE

COLOR LIGHT-TO-FREQUENCY CONVERTER

TAOS099A − AUGUST 2011

7

The LUMENOLOGY

r Company

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Copyright

E 2011, TAOS Inc.

www.taosinc.com

APPLICATION INFORMATION

Power supply considerations

Power-supply lines must be decoupled by a 0.01-

μF to 0.1-μF capacitor with short leads mounted close to the

device package.

Input interface

A low-impedance electrical connection between the device OE pin and the device GND pin is required for

improved noise immunity. All input pins must be either driven by a logic signal or connected to VDD or GND —

they should not be left unconnected (floating).

Output interface

The output of the device is designed to drive a standard TTL or CMOS logic input over short distances. If lines

greater than 12 inches are used on the output, a buffer or line driver is recommended.

A high state on Output Enable (OE) places the output in a high-impedance state for multiple-unit sharing of a

microcontroller input line.

Power down

Powering down the sensor using S0/S1 (L/L) will cause the output to be held in a high-impedance state. This

is similar to the behavior of the output enable pin, however powering down the sensor saves significantly more

power than disabling the sensor with the output enable pin.

Photodiode type (color) selection

The type of photodiode (blue, green, red, or clear) used by the device is controlled by two logic inputs, S2 and

S3 (see Table 1).

Output frequency scaling

Output-frequency scaling is controlled by two logic inputs, S0 and S1. The internal light-to-frequency converter

generates a fixed-pulsewidth pulse train. Scaling is accomplished by internally connecting the pulse-train output

of the converter to a series of frequency dividers. Divided outputs are 50%-duty cycle square waves with relative

frequency values of 100%, 20%, and 2%. Because division of the output frequency is accomplished by counting

pulses of the principal internal frequency, the final-output period represents an average of the multiple periods

of the principle frequency.

The output-scaling counter registers are cleared upon the next pulse of the principal frequency after any

transition of the S0, S1, S2, S3, and OE lines. The output goes high upon the next subsequent pulse of the

principal frequency, beginning a new valid period. This minimizes the time delay between a change on the input

lines and the resulting new output period. The response time to an input programming change or to an irradiance

step change is one period of new frequency plus 1

μs. The scaled output changes both the full-scale frequency

and the dark frequency by the selected scale factor.

The frequency-scaling function allows the output range to be optimized for a variety of measurement

techniques. The scaled-down outputs may be used where only a slower frequency counter is available, such

as low-cost microcontroller, or where period measurement techniques are used.