External Capacitors - Infineon XENSIV BGT60LTR11AIP Manual

XENSIV™ BGT60LTR11AIP Radar Shield2Go
Super low-power 60 GHz Doppler radar sensor with antennas-in-package
Hardware circuits
5.2

External capacitors

The BGT60LTR11AIP MMIC is highly duty-cycled and performs a sample and hold (S&H) operation for lower
power consumption. The S&H switches are integrated into the chip at each differential IQ mixer output port.
They are controlled synchronously via the internal state machine. The capacitors between S&H and the high-
pass filter (HPF) are external. C10, C11, C14 and C15 are 5.6 nF capacitors used as "hold" capacitors for the S&H
circuitry. They can be configured for different pulse-width settings, as shown in Table 10. C8, C9, C12 and C13
are the DC blocking (or high pass) capacitors. They are 10 nF to get a high pass of 4 Hz (if internal high-pass
resistor R = 4 MΩ). It is not recommended to use higher values, as it will affect the analog baseband (ABB)
HP
settling time. The DC blocking capacitors are important because the mixer output has a different DC voltage
than the internal ABB.
Figure 20 External capacitors on the BGT60LTR11AIP Radar Shield2Go
In Figure 20 the external hold (
differential IQ configuration.
Recommended hold capacitors (C10, C11, C14 and C15) for different pulse widths (PW)
Pulse width (µs)
3
5 (default)
10
Charging time of the hold capacitor (
smaller to get it ~ 90 percent charged during one pulse. Rise-time is controlled by the
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internal mixer output resistance of 300 Ω in each branch.
Application Note
) and high-pass capacitors (
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) is limited to the selected pulse width. Shorter pulse widths require
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page 24 of 32
) are shown for all four branches in the
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Hold capacitor value (nF)
4.7
5.6 (default)
15
itself, and the
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V1.0
2022-12-15