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AS7421

Functional Description

Datasheet

• PUBLIC

DS000667

• v2-00 • 2022-Oct-13

│ 17

7.1

Device Architecture

The device features 64 photo diodes (8 x 8 array) with on-chip Fabry-Perot filters. 61 photodiodes

have an individual spectral response in the wavelength range from 750 nm - 1050 nm. The four corner

photodiodes (indicated in the block diagram below with grey shading) share the same filter response

of 830 nm. Sixteen dedicated 16-bit ADCs with adjustable gain and integration time are available and

can be configured with the serial interface. The gain of each ADC can be adjusted independently.

Once a spectral measurement is started, the device automatically runs four full integration cycles to

obtain spectral data of all 64 channels. The spectral data (128 bytes) is stored on chip and can be

read out using the I2C interface burst mode after the four cycles have been finished.

The GPIO can be used to trigger and synchronize a spectral measurement with an external MCU or

as additional interrupt output. The pin RST acts as reset input and is active high.

Figure 13:

Simplified Block Diagram of AS7421

NIR LEDs

LED

Driver

CH0 ADC

CH1 ADC

CH2 ADC

CH3 ADC

CH14 ADC

CH15 ADC

CH0 Data

CH1 Data

CH2 Data

CH3 Data

CH62 Data

CH63 Data

GPIO

VDD

I2C

Interface

SCL

SDA

interrupt

handling

INT

GND

OTP

8x8 photo diode array

CH12 ADC

CH13 ADC

CH60 Data

CH61 Data

16 x 16bit ADC w. adjustable gain

CH0 Gain

CH1 Gain

CH2 Gain

CH3 Gain

CH14 Gain

CH15 Gain

CH12 Gain

CH13 Gain

LED A

RST

OSC

REG.

BANK

GPIO

PGND

TEMP

RAM

AS7421 数据表(PDF) 18 Page - OSRAM GmbH

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