8545-0198-01 Revision 1.9 STX3 Users Manual
9/24/2020 Globalstar, Inc. Confidential and Proprietary Page | 4
2.2 Block Diagram
The basic elements of a design utilizing the STX3 simplex transmitter are shown below.
Figure 4
The STX3 provides separate power supply inputs. The digital power supply input (VDIG) is a low power input which powers the
digital portion of the STX3. This provides the capability to leave the STX3 in a low power consumption state when the transmitter RF
section is idle. The RF power supply input is a high power input which is only required while the STX3 is transmitting a data packet.
Since the transmission duty cycle is very low, this supply may be turned off the majority of the time and only active during the
transmission of a packet. Due to the random nature of the burst transmissions, and open collector output (PWR_EN) is provided by
the STX3 which can directly control the high current supply for VRF. This will ensure that the RF power supply is enabled for the
minimum amount of time to complete each transmission. It may also be monitored by the host to determine when each burst has
been completed without the need to query the STX3 via the serial host interface.
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