GT-1612-MTBD
GPS&Beidou Receiver Module
www.gotop-zzu.com
Page 12 of 35
Revision: V2.0.1-January 2015
Figure 6:
The External Switch Circuit for TIMER
U1 is an integrated power switch component. The part number ADP191 is recommended. U1 also can be
replaced by discrete components.
TIMER pin also can be used to control the EN pin of a LDO.
TIMER and GPS_EN signals form an
“
OR
”
logic via the Schottky diodes D1 and D2. GPS_EN is a GPIO signal
coming from the host.
TIMER is an open drain output signal. When TIMER pin is used, please pull it high by using an external resistor.
R1 is the pull-up resistor for TIMER signal.
Keeping GPS_EN signal low and sending PMTK command“$PMTK225,4*2F” will make GT-1612-MTBD
module enter into backup mode forever. When this command is executed successfully, TIMER signal will be pulled
down to close the power switch, so GT-1612-MTBD module can go into backup mode as the main power VCC is cut
off. For this case, pulling the GPS_EN signal high by host is the only way to wake the module up.
In backup mode, GT-1612-MTBD module stops to acquire and track satellites. UART is not accessible. But the
backed-up memory in RTC domain which contains all the necessary GPS&Beidou information for quick start up and
a small amount of user configuration variables is alive. Due to the backed up memory, EASY technology is available.
The typical consumption in backup mode can be as ow as 20uA.
As the main power supply for VBAT pin is battery. Coin-type rechargeable capacitor such as MS920SE from
Seiko can be used and Schottky diode such as RB520S30T1G from ON Semiconductor is recommended to be used
here for its low voltage drop.
