Rainbow Electronics GM862-GPS - Manual (Page 40)

GM862-GPS Hardware User Guide
1vv0300728 Rev. 8 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 40 of 73
NOTE: The UART input line TXD (rx_uart) of the GM862-GPS is NOT internally pulled up with a resistor, so there
may be the need to place an external 47KΩ pull-up resistor, either the DTR (dtr_uart) and RTS (rts_uart) input lines
are not pulled up internally, so an external pull-up resistor of 47KΩ may be required.
A power source of the internal interface voltage corresponding to the 2.8VCMOS high level is
available at the PWRMON pin on the connector, whose absolute maximum output current is 1mA.
A maximum of 9 resistors of 47 KΩ pull-up can be connected to the PWRMON pin, provided no other
devices are connected to it and the pulled-up lines are GM862-GPS input lines connected to open
collector outputs in order to avoid latch-up problems on the GM862-GPS.
Care must be taken to avoid latch-up on the GM862-GPS and the use of this output line to power
electronic devices shall be avoided, especially for devices that generate spikes and noise such as
switching level translators, micro controllers, failure in any of these condition can severely compromise
the GM862-GPS functionality.
NOTE: The input lines working at 2.8VCMOS can be pulled-up with 47KΩ resistors that can be connected directly to
the PWRMON line provided they are connected as in this example.
NO OTHER devices than those suggested should be powered with the PWRMON line; otherwise the module
functionality may be compromised.
It is important to consider that the added circuit must have consumption lower than 1mA.
In case of reprogramming of the module has to be considered the use of the RESET line to start correctly the
activity.
The preferable configuration is having an external supply for the buffer.