User Manual

34
APDS-9960
INT
SDA
SCL
V
DD
LEDA
1 µF
Voltage
Regulator
Voltage
Regulator
≥ 10 µF
* Cap Value Per Regulator Manufacturer Recommendation
GND
V
BUS
R
P
R
P
R
PI
C*
1 µF
LDR
LEDK
1 µF
Voltage
Regulator
≥ 10 µF
1 µF
22 Ω
APDS-9960
INT
SDA
SCL
V
DD
LEDA
GND
V
BUS
R
P
R
P
R
PI
LDR
LEDK
Application Information Hardware
Figure 14a. Circuit Implementation using Separate Power Supplies
Figure 14b. Circuit Implementation using Single Power Supply
If operating from a single supply, use a 22-Ω resistor in
series with the VDD supply line and a 1-μF low ESR capaci-
tor to lter any power supply noise. The previous capaci-
tor placement considerations apply. However note that
where LED current is boosted beyond 100mA, it is recom-
mended that the LEDA pin be connected to a separate
power supply.
VBUS in the above gures refers to the I²C bus voltage
which is either VDD or 1.8 V. The I²C signals and the In-
terrupt are open-drain outputs and require pull−up resis-
tors. 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.
In a proximity sensing system, the internal IR LED can be
pulsed by more than 100mA 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.
In many systems, there is a quiet analog supply and a noisy
digital supply. By connecting the quiet supply to the VDD
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 VDD pin and another at the LEDA pin,
along with a bulk storage capacitor (≥ 10μF) at the output
of the LED voltage regulator to supply the current surge.