Data Sheet
AS7265x
Design Considerations
ams Application Note Page 8
[v1-5] 2018-May-23 Document Feedback
Please note, the typical schematic here is configured as UART interface by default so there are no
pull-up resistors on AS72651 I
2
C slave interface. If I
2
C slave interface is needed, please add the pull-
up resistors on either the controller side or on AS72651 I
2
C interface.
3.3 Light Source Selection
Figure 5. Generic Application
Target
Reflective
Surface
100nF
RX / SCL_S
GND
LED_DRV
SCK
CSN_EE
MISO
MOSI
VDD1
VDD2
Multispec
uP
10uF
3V
3V
TX / SDA_S
LED_IND
3V
Flash
18
Channel
Sensor
Light
Source
LightIn
INT
Figure 5 shows AS7265x Multispectral Chipset generic application. AS7265x chipset produce the
sensor output data based on the received reflection light rays from the target. The light source
selection would be dependent on the spectral responsivity of reflected light and characteristics of the
target. For example, if the target is expected to absorb 610nm light in visible range and the application
needs to distinguish the target from others, a broadband white LED might be used as the light source
for AS7265x and AS7265x 610nm channel should be checked. Various applications may require
different light sources.
3.4 Other Connections
The AS72651 device needs a flash memory to store the firmware and the data. The flash memory
should be at least 2-Mbits operating at SPI mode 0 with byte write supported. With CSN_SD
i
pin and
RESN pin, AS72651 supports various flash memory programming methodologies. Please refer to
Application Note “AS72xx Flash program and update”.
The LED, D11 in the typical schematic, is recommended for debugging purpose. During AS72651
power up, D11 should be on for a short time and off. If D11 is blinking, it indicates there is an issue
with accessing the flash memory content.
The AS72651/AS72652/AS72653 devices require a 3.3V supply on both VDD1 and VDD2 pins
associated with the decoupling capacitors, C7/C8, C10/C11, and C12/C13 in the schematic. Each
LED_DRV pin on AS72651/AS72652/AS72653 can drive external LED sources with various amount
of sink currents. The LED current can be configured as 12.5mA, 25mA, 50mA and 100mA.