Application Note
page 13 of 33
V1.7
2022-08-01
XENSIV™ BGT60LTR11AIP shield
60 GHz radar system platform
Hardware description
3.8
LEDs and level shifting
The shield has two LEDs to indicate the motion detection (green) and target
’s direction of
motion (red), as
shown in Figure 14, where R1 and R2 are limiting resistors. The digital block within the detector in the MMIC
evaluates and sets the Target detect/Phase detect outputs of the BGT60LTR11AIP MMIC. Target detect (TDet)
output is active low. Phase detect (PDet) output is used to show the direction of the detected target. It is set to
high for approaching targets, otherwise low. The default state for PDet is low.
The outputs from MMIC are at the voltage level of 1.5 V. They are level-shifted to the voltage level of V
in
by using
the circuit shown in Figure 14. In the circuit, BGT_TARGET_DET and BGT_PHASE_DET are outputs of MMIC (1.5 V
voltage level). V
DD_RF
is 1.5 V and V
in
is 3.3 V (when connected with Radar Baseboard MCU7).
•
When BGT_TARGET_DET is high (1.5 V), NMOS is off (V
gs
= 0 V), and Target_Det_Out is 3.3V through the R14
pull-up resistor.
•
When BGT_TARGET_DET is low (0 V), NMOS is on (V
gs
= 1.5 V), and Target_Det_Out is pulled down to 0 V.
The same applies to the BGT_PHASE_DET signal.
Table 3
LED detection
LED
Mode
Comments
Green
On
–
target detected
Off
–
target not detected
Target_Det_Out is an active low signal
Red
On
–
target departing
Off
–
target approaching
Phase_Det_Out is an active low signal
Figure 14
Connections of the LEDs and level shifter
VDD_RF
Vin
1
2
6
Q1A
BSD840N
R13
100k
R14
10k
Target_Det_Out
BGT_TARGET_DET
VDD_RF
Vin
5
3
4
Q1B
BSD840N
R15
100k
R16
10k
Phase_Det_Out
BGT_PHASE_DET
Vin
Vin
R1
1k
R2
1k
1
2
T
Green LED
1
2
P
Red LED
Phase_Det_Out
Target_Det_Out
