User Guide

System Module LG4 and Grip Module LS4 CCS Technical Documentation
Page 28 ¤Nokia Corporation Issue 2 11/02
comparators with adjustable thresholds in the receiver.
Proximity detector block enables several pulse width and pulse frequency selections and
emitter current can be controlled with a current sensing resistor. In NHL-2NA emitter
current is 100mA, pulse width 8Ps and pulse frequency 500/2000Hz.
Proximity Detector components
Lightguides
Lightguides are needed to guide emitted IR radiation outside the phone as well as to
guide the reflected pulses into the phone to the photodiode. Half angle of the emitted
radiation is 10q. This means, that most of the emitted radiation is reflected from a circle
that has diameter 20mm, when the target is at 50mm distance. Receiver lightguide col-
lects radiation and guides it to the photodiode. Optical insulator, made of black rubber,
surrounds the photodiode so that it cannot receive any radiation that is reflected inside
the phone.
Self-monitoring signal is created with small reflector areas and curved top surfaces in
the lightguides. Reflectors are placed inside the phone, so that they are subject to as lit-
tle wearing as possible.
IRED
The IRED type is CL-200-IR-X-TU (NMP CODE 4860009), which has high radiant intensity
and relatively small half angle (28°). Maximum forward current is 100mA (pulsed 1A) and
V
f
=1.3V. Rise Time is 2Ps, total radiant intensity 12mW (at 50mA current) and peak
radiant intensity at 950nm.
Photodiode
The photodiode is BPW34FS (NMP CODE 486J830). It has peak sensitivity at 950nm and
filtering for visible light. Photodiode receives radiation from 60° half angle and its rise
time is 20ns.
HW Implementation
The implementation of the proximity sensor is described in figure 16. Note that VTOUCH
is connected externally to VANA.