Si1102
12 Rev. 1.0
4. Pin Descriptions—Si1102
Figure 11. Pin Configuration
Table 5. Pin Descriptions
Pin Name Type Description
1 PRX Output Proximity Output.
Normally high; goes low when proximity is detected. When device is not
enabled, the PRX pulls-up to V
DD
.
2TXGDGround
TXGD.
Transmit ground (includes PRX return and other digital signals).
Must be connected to VSS.
3 TXO Output
Transmit Output Strobe.
Normally connected to an infrared LED cathode. This output can be allowed
to saturate, and output current can be limited by the addition of a resistor in
series with the LED. It can also be connected to an independent unregulated
LED supply even if the V
DD
supply is at 0 V without either drawing current or
causing latchup problems.
4 NC Do not connect.
5VDD Input
Power Supply.
2 to 5.25 V voltage source
6 SREN Input
Sensitivity Resistor/ENable.
Driving SREN below 1 V or connecting resistance from SREN to VSS
enables the chip and immediately starts a proximity measurement cycle. A
potentiometer to VSS controls proximity sensitivity. R1 = 0 yields maximum
detection distance. If SREN is high and FR is low (SREN = V
DD
, FR = 0), part
is in shutdown.
7 FR Input
Frequency Resistor.
A resistor to VSS controls the proximity-detection cycle frequency. With no
resistor, the sample frequency is, at most, 5.0 Hz. With FR shorted to VSS
the sample frequency is typically 250 Hz. With a 100 k
resistor, the sample
frequency is typically 7 Hz, maximum 30 Hz. The voltage on FR relative to
ground is only about 30 mV.
8 VSS Ground
VSS.
Ground (analog ground).
PRX
TXGD
TXO
NC
VSS
FR
SREN
VDD
1
2
3
4
8
7
6
5
