TMD37821 Datasheet, PDF (27/34 Pages) TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS – Color Light-To-Digital Converter with Proximity Sensing

Application Information
Figure TMD3782 – 41:
Typical Application Hardware Circuit
In a proximity sensing system, the IR LED can be pulsed by the
TMD3782 with more than 100 mA of rapidly switching current,
therefore, a few design considerations must be kept in mind to
get the best performance. The key goal is to reduce the power
supply noise coupled back into the device during the LED
pulses. If V_bat does not exceed the maximum specified LDR pin
voltage (including when the battery is being recharged), LEDA
can be directly tied to V_bat for best proximity performance.
In many systems, there is a quiet analog supply and a noisy
digital supply. By connecting the quiet supply to the V_DD pin
and the noisy supply to the LED, the key goal can be meet. Place
a 1-μF low-ESR decoupling capacitor as close as possible to the
V_DD pin and another at the LED anode, and a 10 - 22μF bulk
capacitor at the output of the LED voltage regulator to supply
the 100-mA current surge.
If operating from a single supply, use a 22-Ω resistor in series
with the V_DD supply line and a 1-μF low ESR capacitor to filter
any power supply noise. The previous capacitor placement
considerations apply.
Datasheet - Mar. 2013 - V2
V_BUS in the above figure refers to the I²C bus voltage which is
either V_DD or 1.8 V. Be sure to apply the specified I²C bus voltage
shown in the Available Options table for the specific device
being used.
The I²C signals and the Interrupt are open-drain outputs and
require pull−up resistors. The pull-up resistor (RP) value is a
function of the I²C bus speed, the I²C bus voltage, and the
capacitive load. The ams EVM running at 400 kbps, uses 1.5-kΩ
resistors. A 10-kΩ pull-up resistor (RPI) can be used for the
interrupt line.
TMD3782 – 27