TSL250RD, TSL251RD, TSL260RD, TSL261RD
LIGHT-TO-VOLTAGE OPTICAL SENSORS
TAOS050K ï OCTOBER 2007
6
r
r
Copyright E 2007, TAOS Inc.
The LUMENOLOGY r Company
www.taosinc.com
APPLICATION INFORMATION
Power Supply Considerations
For optimum device performance, power-supply lines should be decoupled by a 0.01-PF to 0.1-PF capacitor
with short leads connected between VDD and GND mounted close to the device package.
Device Operational Details
The voltage developed at the output pin (OUT) is given by:
V
O
= V
D
+ (R
e
) (E
e
)
where:
V
O
is the output voltage
V
D
is the output voltage for dark condition (E
e
= 0)
R
e
is the device responsivity for a given wavelength of light given in mV/(PW/cm
2
)
E
e
is the incident irradiance in PW/cm
2
V
D
is a fixed offset voltage resulting primarily from the input offset voltage of the internal op amp. As shown in
the equation above, this voltage represents a constant, light-independent term in the total output voltage V
O
.
At low light levels, this offset voltage can be a significant percentage of V
O
. For optimum performance of any
given device over the full output range, the value of V
D
should be measured (in the absence of light) and later
subtracted from all subsequent light measurements (see Figures 2 and 3).
PCB Pad Layout
Suggested PCB pad layout guidelines for the D package is shown in Figure 9.
2.25
6.90
4.65
1.27
0.50
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
Figure 9. Suggested D Package PCB Layout
