Crystal Oscillator - Infineon XENSIV BGT60LTR11AIP Manual

XENSIV™ BGT60LTR11AIP Radar Shield2Go
Super low-power 60 GHz Doppler radar sensor with antennas-in-package
Hardware circuits
The shield has two LEDs to indicate the motion detection (blue) and the target's direction of motion (red), as
shown in Table 9. R10 and R11 are current-limiting resistors. The digital block within the detector in the MMIC
evaluates and sets the TD/PD outputs of the BGT60LTR11AIP MMIC. Target detected (TD) output is active low. It
is set to low when enough events on the pulse train are counted. Phase detected (PD) output is used to show
the direction of the detected target. It is only valid in the case of a detected target, and it is set to high for
approaching targets and set to low for departing targets.
Figure 18 LED schematics
For the TD pin, when no target is detected, the voltage level appears to be 3.3 V on this pin. The PD pin voltage
varies, depending on the direction of the moving object. While the target is approaching, the pin puts out 3.3 V,
and when the target is departing from the radar it puts out close to 0 V. These pins can be read from analog pins
or digital pins TD and PD.
Additionally, the yellow LED1 can be controlled with P10 via an external GPIO of a microcontroller and serves as
a custom user LED. Unsolder jumper J1 if you want to disconnect LED1 from P10. Figure 18 shows the
schematics of the four LEDs.
5.1

Crystal oscillator

The MMIC requires an oscillator source with a stable reference clock providing low phase jitter and low phase
noise. The oscillator is integrated inside the MMIC. This saves current consumption, as crystal oscillators
consume only a few milli-amperes and run continuously. The Radar Shield2Go uses a 38.4 MHz crystal
oscillator, as seen in Figure 19.
Figure 19 Oscillator circuit with 38.4 MHz crystal
Application Note page 23 of 32 V1.0
2022-12-15