tsl237 TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS, tsl237 Datasheet - Page 5

• Manufacturer Part Number: tsl237
• Description: High-sensitivity Light-to-frequency Converter
• Manufacturer: TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS

Power-Supply Considerations
Device Operational Details
Output Interface
The LUMENOLOGY r Company
Power-supply lines must be decoupled by a 0.01-μF to 0.1-μF capacitor with short leads placed close to the
TSL237 (Figure 3). A low-noise power supply is required to minimize jitter on output pulse.
The frequency at the output pin (OUT) is given by:
where:
f
independent of light intensity. The TSL237 die is trimmed to minimize the magnitude of this dark frequency
component so that it can be neglected in the transfer function calculation. In many applications, measurement
of the actual dark frequency may be impractical due to measurement times ranging from several seconds to
several minutes, and the fact that some devices may never transition (zero dark frequency).
The output of the device is designed to drive a CMOS logic input over short distances. If lines greater than 12
inches in length are used on the output, a buffer or line driver is recommended.
D
is a constant error term in the output frequency calculation resulting from leakage currents, and is
f
f
R
E
O
D
e
e
is the output frequency
is the output frequency for dark condition (E
is the device responsivity for a given wavelength of light given in kHz/(μW/cm
is the incident irradiance in μW/cm
0.1 μF
Figure 8. Typical TSL237 Interface to a Microcontroller
f
O
= f
GND
APPLICATION INFORMATION
TSL237
D
r
V
+ (R
DD
V
DD
e
) (E
www.taosinc.com
e
2
)
OUT
e
= 0)
Timer / Port
LIGHT-TO-FREQUENCY CONVERTER
MCU
r
2
)
TAOS052G − SEPTEMBER 2007
HIGH-SENSITIVITY
Copyright E 2007, TAOS Inc.
TSL237
5