TSL2581 Datasheet, PDF (24/32 Pages) TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS – LIGHT-TO-DIGITAL CONVERTER

TSL2581, TSL2583
LIGHT-TO-DIGITAL CONVERTER
TAOS134 − MARCH 2011
APPLICATION INFORMATION: HARDWARE
Power Supply Decoupling and Application Hardware Circuit
The power supply lines must be decoupled with a 0.1 μF capacitor placed as close to the device package as
possible (Figure 6). The bypass capacitor should have low effective series resistance (ESR) and low effective
series inductance (ESI), such as the common ceramic types, which provide a low impedance path to ground
at high frequencies to handle transient currents caused by internal logic switching.
V_BUS
V_DD
R_P
R_P
R_PI
TSL2581/
TSL2583
0.1 mF
INT
SCL
SDA
Figure 6. Bus Pull-Up Resistors
Pull-up resistors (R_P) maintain the SCL and SDA lines at a high level when the bus is free and ensure the signals
are pulled up from a low to a high level within the required rise time. The I²C bus protocol was developed by
Philips (now NXP). The pull-up resistor (R_P) value is a function of the I²C bus speed, the supply voltage, and
the capacitive bus loading. Users should consult the NXP I²C design specification
(http://www.i2c−bus.org/references/) for assistance. With a lightly loaded bus running at 400 kbps and
V_BUS = 3 V, 1.5 kΩ resistors have been found to be viable.
A pull-up resistor (R_PI) is also required for the interrupt (INT), which functions as a wired-AND signal in a similar
fashion to the SCL and SDA lines. A typical impedance value between 10 kΩ and 100 kΩ can be used.
Copyright E 2011, TAOS Inc.
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