User's Manual

Table Of Contents
MC55/56 Hardware Interface Description
Confidential / Preliminary
s
MC55/56_hd_v03.00 Page 28 of 104 16.08.2005
3.3.1.1 Turn on MC55/56 using the ignition line /IGT (Power on)
To switch on MC55/56 the /IGT (Ignition) signal needs to be driven to ground level for at least
100ms and not earlier than 10ms after the last falling edge of VDD. This can be
accomplished using an open drain/collector driver in order to avoid current flowing into this
pin.
Software
controlled
/EMERGOFF
ca. 300ms ca. 900ms
Serial interfaces
ASC0 and ASC1
Undefined
Inactive
Active
VDD
ca. 60ms
/TXD0
/TXD1
/DSR0
BATT+
/IGT
min. 10ms
min.
100ms
HiZ
HiZ
Figure 3: Power-on by ignition signal
In a battery operated MC55/56 application, the duration of the /IGT signal must be 1s
minimum when the charger is connected and you may want to go from Charge only mode to
Normal mode.
For details
p
lease see Cha
p
ter 3.3.1.2