Техническая Спецификация для Microchip Technology DM240015
MPLAB
®
Starter Kit for Intelligent.Integrated.Analog User’s Guide
DS50002172A-page 16
2013 Microchip Technology Inc.
9.
Digital Temperature Sensor (U9) and Jumper, JP7
The TC77 is a digital temperature sensor in a SOT-23 package. It uses an SPI interface
to communicate to the microcontroller. The TC77 is powered as part of the
SWITCHED_VDD
to communicate to the microcontroller. The TC77 is powered as part of the
SWITCHED_VDD
bus.
When installed (default), jumper, JP7, connects the TC77 chip select to port pin, RE9.
If the TC77 is not needed, removing JP7 allows port pin, RE9, to be used as a
general purpose I/O resource.
If the TC77 is not needed, removing JP7 allows port pin, RE9, to be used as a
general purpose I/O resource.
10. Indoor Ambient Light Sensor (Q1)
Q1 is a phototransistor, used to detect indoor ambient light level. The sensor is designed
to output a current in the range of 5 µA to 300 µA, as the light flux varies from 10 to
1000 lux. This current flows through R11, causing a voltage of V
to output a current in the range of 5 µA to 300 µA, as the light flux varies from 10 to
1000 lux. This current flows through R11, causing a voltage of V
DD
– (I
SENSOR
/R11) to
be applied to analog input pin, AN22. The resulting DC voltage is inversely proportional
to the amount of light on the sensor, ranging from 3.3V (dark) to 50 mV (very bright).
The value of R11 (27 kΩ) limits the upper light level to approximately 400 lux. (As a
reference, the average ambient light in an office is 300 to 400 lux.)
to the amount of light on the sensor, ranging from 3.3V (dark) to 50 mV (very bright).
The value of R11 (27 kΩ) limits the upper light level to approximately 400 lux. (As a
reference, the average ambient light in an office is 300 to 400 lux.)
11. Audio Output Driver and Output Jack (3.5 mm)
The microcontroller’s two 10-bit DACs are connected via buffer op amp, U3
(MCP6022), to this jack. DAC1 (port pin, RG9) is connect to the right channel and
DAC2 (port pin, RB13) is connected to the left channel. The op amp is configured as a
unity gain buffer. The op amp buffer is powered from the SWITCHED_VDD bus.
A simple RC filter with a cut point of -3 dB point at 16 kHz is in series with each output.
When connecting to a high-impedance input (such as external powered speakers), the
15Ω series resistor has little effect on the amplitude.
(MCP6022), to this jack. DAC1 (port pin, RG9) is connect to the right channel and
DAC2 (port pin, RB13) is connected to the left channel. The op amp is configured as a
unity gain buffer. The op amp buffer is powered from the SWITCHED_VDD bus.
A simple RC filter with a cut point of -3 dB point at 16 kHz is in series with each output.
When connecting to a high-impedance input (such as external powered speakers), the
15Ω series resistor has little effect on the amplitude.
12. Electret Microphone
This is a simple, unamplified microphone, which is biased at 1/2 of the SWITCHED_VDD
voltage (about 1.65V). The output is AC-coupled and brought out to Pin 5 of J7/J8. For
voice use, the output will need to be boosted to approximately 20X.
voltage (about 1.65V). The output is AC-coupled and brought out to Pin 5 of J7/J8. For
voice use, the output will need to be boosted to approximately 20X.
13. Precision Voltage Reference Section Jumper (J9)
The jumper selects the on-board, precision 2.5V voltage reference or an externally
applied reference on the CH1+ (default) connection on J7/J8 for use with the
Sigma-Delta A/D Converter. The default configuration is V
applied reference on the CH1+ (default) connection on J7/J8 for use with the
Sigma-Delta A/D Converter. The default configuration is V
DD
as the reference, which
is also the default configuration for the preprogrammed demonstration.
For low noise and more accurate measurements, the 2.5V precision reference is
required. Since the input range of the A/D is V
For low noise and more accurate measurements, the 2.5V precision reference is
required. Since the input range of the A/D is V
SS
to V
REF
, using the 2.5V reference
reduces the converter’s input range.
Note:
Each DAC is capable of driving full-scale levels (i.e., 3.3V p-p). The
15Ω limiting resistor, in series with the outputs, should limit the output to a
standard 16Ω headset to approximately 1.5V maximum. However, this
level may exceed safe listening levels. When driving headphones, it is
recommended that the output level be kept under 200 mV p-p.
15Ω limiting resistor, in series with the outputs, should limit the output to a
standard 16Ω headset to approximately 1.5V maximum. However, this
level may exceed safe listening levels. When driving headphones, it is
recommended that the output level be kept under 200 mV p-p.