Datasheet

Designing the VEML6070 UV Light Sensor
Into Applications
Application Note
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Vishay Semiconductors
APPLICATION NOTE
Revision: 26-Mar-18
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Document Number: 84310
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THE VEML6070’S ACK SIGNAL
The VEML6070 features a function for sending an acknowledge signal (ACK) to the microcontroller when the UV value changes
are bigger than one of two pre-programmable step sizes: ACK_THD. The purpose of the ACK signal is similar to an interrupt
feature, which informs the μC once the sensed data level goes below or beyond the interrupt threshold setting. The ACK
threshold values are 102 steps and 145 steps.
There are two methods for driving acknowledge conditions and read / write commands to the VEML6070:
If the host implements the INT function, it performs a modified received byte operation to disengage the VEML6070’s
acknowledge signal and acknowledge alert response address (ARA), 0x18 (hex). A command format for responses to an ARA
looks like this:
Please note the following:
1. When the VEML6070 is connected to V
DD
, the sensors may be in an undefined state. This may lead to an initially active
interrupt, even though no measurements have been made i.e. no threshold has been crossed
2. When the interrupt is active, only the ARA register can be accessed, as the other registers are blocked until the interrupt is
cleared and these will respond with a “NACK” when an attempt is made to access them. The interrupt is cleared by reading
the ARA register
3. It is therefore mandatory to clear this interrupt after power on, so that the sensor settings can be accessed and used to make
measurements
4. It is possible that after the first time one reads the ARA register the interrupt is not directly cleared and the access to the
control registers are still blocked. One may need to clear it again. Therefore it is recommended that one reads the ARA
register until it responds with a “NACK” to be certain that the interrupt has been cleared successfully
5. If the interrupt function of the sensor is no longer used in the application from this point onwards, no further care needs to
be taken in regard of the ARA register
6. If the interrupt function is used, please be sure to follow the above instructions to clear the interrupt again before attempting
to access the sensor settings
For the hardware circuit design, this pin should be connected to an INT pin or GPIO pin of the MCU. The threshold ACK_THD
definition is based on the sensitivity setting of the VEML6070.
The ACK or UVI interrupt function allows the UVI sensing system to perform data polling based on the interrupt event. The
system sensor manager does not need to do continual data polling and this significantly reduces the MCU loading. The ACK
signal can also be used as a trigger event for popping up a warning UVI message.
0x70, bit 5 ACK
0: disabled
1: enabled
0x70, bit 4 ACK_THD
0: 102 steps
1: 145 steps
S ARA (0x18) Rd A UVS Slave Address A P