MAX-M10S-Integration manual
Figure 37: Typical 1.8 V design
B.2 Antenna supervisor designs
Figure 38 and Figure 39 show a reference design for a 2-pin and 3-pin antenna supervisor design
respectively. Here are some key features:
• VCC and V_IO are connected together to a single supply.
• Supply at V_BCKP is optional. If present, the hardware backup mode is supported. This mode
maintains the time and GNSS orbit data in the battery-backed RAM memory if the main supply
is switched off.
If there is no backup supply, the EXTINT pin can be used for time aiding and the GNSS orbit data
can be aided using AssistNow services or downloaded to the host and fed back to the receiver
at startup.
• An external SAW filter can be placed on the RF path as shown in Figure 38, which allows an SAW-
LNA-SAW RF front-end circuit for improving out-of-band immunity against RF interference from
other sources. This is especially useful when MAX-M10S is used in cellular applications.
• An active antenna can be supplied with the VCC_RF output from MAX-M10S or from an external
supply. VCC_RF is a filtered output voltage supply, which outputs VCC - 0.1 V. In addition, the
active antenna supply can be turned on/off by the LNA_EN signal, which also controls the internal
LNA of MAX-M10S.
• External open drain buffers and operational amplifiers are also needed depending on whether a
2-pin or 3-pin antenna supervisor design is used.
• UART and I2C communication interfaces are available. I2C PIOs (SDA and SCL) can be used in a
3-pin antenna supervisor design as shown in Figure 39. In this case, the I2C interface needs to be
disabled before assigning the new function to the PIOs.
Disable the I2C interface with the CFG-I2C-ENABLED configuration key when I2C pins are
used for antenna supervisor functions. Likewise, disable the UART interface (CFG-UART1-
ENABLED) or TIMEPULSE (CFG-TP-TP1_ENA) when the pins are used for antenna supervisor
functions.
UBX-20053088 - R03
Appendix Page 83 of 89
C1-Public
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