ISL29038
13
FN7851.1
January 23, 2015
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Soldering Considerations
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic ODFN
package does not require a custom reflow soldering profile. A
standard reflow soldering profile with a +260°C maximum is
recommended. Additional information regarding soldering
ISL29038 is included in Intersil Technical Brief TB477
.
Suggested PCB Footprint
Refer to TB477,“Surface Mount Assembly Guidelines for Optical
Dual FlatPack No Lead (ODFN) Package” before starting ODFN
product board mounting.
Additional information regarding soldering is also included in
Intersil Technical Brief TB477
.
PCB Layout Considerations
The ISL29038 is relatively insensitive to PCB layout. Adherence
to the following guidelines will ensure first pass success and best
performance.
Route the I
2
C/SMBus SCL, SDA and the INT traces away from
sources of switching noise. A 499k 1% tolerance resistor must be
connected from the REXT pin to AGND. This node also needs to
be isolated from any switching noise.
ISL29038 pins IRGND and AGND should connect to a low
impedance ground with low resistance and low inductance
traces. Ferrite beads and inductors should be avoided in the
ground path. If necessary, due to RF consideration, the effects of
DCR (DC resistance) should be evaluated on ALS and Proximity
system performance.
A 1µF ceramic decoupling capacitor should be placed as close to
the AVDD pin as possible.
The ISL29038 drives the IR LED with 0.09ms current pulses. To
supply this pulsed current, a 1 to 10µF bulk decoupling capacitor
(C
1
) must be connected from the IR LED anode to the GNDIR pin
to minimize instantaneous resistive voltage drop. The connection
from IR LED cathode to the IRDR pin should be short and with
minimal inductance. Similarly, connection from the IR LED to
VDD must be made with a low impedance trace.
For most applications, a single power supply may be used to
power the IR LED and the ISL29038. Use of resistor R
2
and
capacitor C
2
(Figure 13) to help filter out the power supply noise
generated from IR LED switching is recommended for best
ISL29038 performance when using a single power supply. For
dual supply operation, resistor R
2
should not be installed.
FIGURE 13. 8 LD ODFN SENSOR LOCATION OUTLINE - DIMENSIONS IN mm
2.00
2.10
1
2
3
4
8
7
6
5
0.57
ALS SENSOR
OFFSET 0.03mm
ALS SENSOR AREA
0.66mm x 0.24mm
PROX SENSOR
OFFSET 0.42mm
PROX SENSOR AREA
0.57mm x 0.16mm
