Nordic 3 - Infrared LED and Driver; Codec

5 Hardware description: Smart Remote 3 DK add-on
Doc. ID 4374_139 v1.1
Page 36
3V3
VCC
SHDN
6
GND
1
VOUT
3
C
-
5
C
+
4
VIN
2
U9
LTC3240EDC-3.3
C53
1.0
µ
F
C49
1.0
µ
F
C54
4.7
µ
F
Q1
FDV303N
R2
220R
DISCHARGE
TP SHDN
R25
1M0
VCC
R31
1M0
Figure 24: Voltage regulator for the trackpad
Important: The input voltage for this regulator is 1.8 V–5.5 V.
5.3.6 Infrared LED and driver
To support legacy products, the remote control has an infrared LED with a driver circuit.
The infrared LED is driven by a transistor (Q3) to offer higher current than the MCU I/O can offer.
Q3
FDV303N
R23
2R2
IR_LED
SB28
R1
1M0
VIO
LD1
IR333C/H2
C37
100µF
Figure 25: Infrared LED and driver circuit
The control signal is active high meaning that when the IR_LED signal has logic high level, the LED emits
infrared light.
5.3.7 Codec
A codec is used in conjunction with the nRF51 DK to get the analog signal from the microphone to digital
signals.
For codec, the ES8218 from Everest Semiconductor is chosen. ES8218 is set up with the use of two-wire
interface. The microphone signal is transferred to the nRF51 DK via I
2
S interface.