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AS3935

Datasheet - Detailed Descri p ti on

8.1 Circuit

Figure 1 shows a block diagram of the AS3935. The external antenna is directly connected to the Analog Front-end (AFE), which amplifies and

demodulates the received signal. The watchdog continuously monitors the output of the AFE and alerts the integrated lightning algorithm block in

the event of an incoming signal. The lightning algorithm block validates the signal by checking the incoming signal pattern, calculates the energy

and then the AS3935 provides the MCU with an estimate of the distance to the head of the storm. The lightning algorithm block, processing the

demodulated signal, can distinguish between lightning signal and man-made disturbers. If the received signal is classified as a man-made

disturber, then the event is rejected and the system automatically goes back into listening mode to minimize current consumption. If the incoming

signal identifies a lightning event, then the statistical distance estimation block performs an estimation of the distance to the head of the storm

(Typical time needed 2ms).

The LC oscillator together with the calibration block can calibrate both the TRCO and the SRCO clock generator to compensate process

variations.

8.2 Operating Modes

Power-down Mode.

In Power-down Mode, the entire AS3935 is switched off to reduce the current consumption to minimum (typ 1µA).

Listening Mode.

In listening mode the AFE, the watchdog, the noise floor level generation, the bias block, the TRCO, and the voltage regulator (in case it is

enabled) are running. In this mode the system can push down the power consumption to a minimum (typ 60µA). In case the maximum voltage

supply does not exceed 3.6V, it is possible to switch off the voltage regulator to save power.

Signal Verification.

The AS3935 enters in this mode every time the watchdog detects dynamic activity picked up by the antenna. Threshold can be set in WDTH

REG0x01[3:0]. The IC will leave this mode either if the incoming signal is classified as disturber or if the analysis of the single event (lightning) is

finished. If the received signal is classified as a disturber, then the AS3935 will automatically go back to listening mode without any needed

action from outside and an interrupt will be generated (with option bit this interrupt can be masked). If the received pattern matches all

requirements, the energy calculation is performed and the AS3935 provides distance estimation.

8.3 System and Block Specification

8.3.1 Register Table

Table 8. Register Table

Register #

7

6

5

4

3

2

1

0

0x00

Reserved

AFE_GB

PWD

0x01

Reserved

NF_LEV

WDTH

0x02

Reserved

CL_STAT

MIN_NUM_LIGH

SREJ

0x03

LCO_FDIV

MASK_DIST

Reserved

INT

0x04

S_LIG_L

0x05

S_LIG_M

0x06

Reserved

S_LIG_MM

0x07

Reserved

DISTANCE

0x08

DISP_LCO

DISP_SRCO

DISP_TRCO

Reserved

TUN_CAP

0x09

Lightning Detection Look-up Table

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0x32