APDS-9130 Datasheet, PDF (23/31 Pages) AVAGO TECHNOLOGIES LIMITED – Digital Proximity Sensor

Application Information: Hardware
In a proximity sensing system, the included IR LED can be pulsed 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. Averaging of multiple proximity samples is
recommended to reduce the proximity noise.
The first recommendation is to use two power supplies; one for the device V_DD and the other for the IR LED. 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 LEDA pin, the key goal can be met. Place a 1 μF low-ESR decoupling capacitor as close as possible to
the V_DD pin and another at the LEDA pin, and at least 10 μF of bulk capacitance to supply the 100 mA current surge. This
may be distributed as two 4.7 μF capacitors.
Voltage
Regulator
Voltage
Regulator
1 µF
C*
≥ 10 µF
1 µF
LEDK
V _DD
LDR
GND APDS-9130
INT
SCL
LEDA
SDA
V _BUS
R_P
R_P
R _PI
* Cap Value Per Regulator Manufacturer Recommendation
Figure 12a. Proximity Sensing Using Separate Power Supplies
If it is not possible to provide two separate power supplies, the device can be operated from a single supply. A 22 Ω
resistor in series with the V_DD supply line and a 1 μF low ESR capacitor effectively filter any power supply noise. The
previous capacitor placement considerations apply.
Voltage
Regulator
≥ 10 µF
1 µF
22 Ω
1 µF
LEDK
V _DD
LDR
GND APDS-9130
INT
SCL
LEDA
SDA
V _BUS
R_P
R_P
R _PI
Figure 12b. Proximity Sensing Using Single Power Supply
V_BUS in the above figures refers to the I²C bus voltage. The I²C signals and the Interrupt are open-drain outputs and
require pull-up resistors. The pull-up resistor (R_P) value is a function of the I²C bus speed, the I²C bus voltage, and the
capacitive load. A 10 kΩ pull-up resistor (R_PI) can be used for the interrupt line.
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