Integration Manual

HMS1 Hardware Interface Description
Confidential / Preliminary
s
HMS1_HD_V01.62 Page 20 of 39 2006-08-21
Example: If the length of the flex cable reaches the maximum length of 100mm, this
connection may cause, for example, a resistance of 30mΩ in the BATT+ line and
30mΩ in the GND line. As a result, a 2A transmit burst would add up to a total
voltage drop of 120mV. Plus, if a battery pack is involved, further losses may
occur due to the resistance across the battery lines and the internal resistance of
the battery including its protection circuit.
Figure 3: Power supply limits during transmit burst
3.3. Power-Up / Power-Down Scenarios
In general, be sure not to turn on HMS1 while it is beyond the safety limits of voltage and
temperature. HMS1 would immediately switch off after having started and detected these
inappropriate conditions. In extreme cases this can cause permanent damage to the module.
3.3.1. Turn on HMS1
When the HMS1 module is in Power-down mode, it can be started to Normal mode or
Airplane mode by driving the IGT (ignition) line to ground. This must be accomplished with an
open drain/collector driver to avoid current flowing into this pin.
3.3.1.1. Reset or Turn off HMS1 in Case of Emergency
Caution: Use the EMERG_RST pin only when, due to serious problems, the software is not
responding for more than 5 seconds. Pulling the EMERG_RST pin causes the loss of all
information stored in the volatile memory. Therefore, this procedure is intended only for use
in case of emergency, e.g. if HMS1 does not respond, if reset or shutdown via AT command
fails.
The EMERG_RST signal is available on the application interface.
3.3.2. Turn off HMS1
HMS1 can be turned off by Normal shutdown: Software controlled by AT command.
Be sure not to disconnect the supply voltage V
BATT+
. Otherwise you run the risk of losing
data.
Transmit
burst 2A
Transmit
burst 2A
Rippl
e
Drop
min. 3.3V
BATT+