Xplore Technologies Corp. MC7750 Manual Do Utilizador
Power
Rev 4 Sep.11
Proprietary and Confidential - Contents subject to change
49
Figure 6-1: Voltage / temperature monitoring state machines
Power interface
Power ramp-up
On inital power up, inrush current depends on the power supply rise time — turn
on time >100 µs is required for < 3A inrush current.
on time >100 µs is required for < 3A inrush current.
The supply voltage must remain within specified tolerances while this is occurring.
Power-up timing
The unit is ready to enumerate with a USB host within a maximum of 3–5
seconds after power-up.
seconds after power-up.
on page 49 illustrates the power-up timing
sequence.
Figure 6-2: Power-up timing diagram
Note: Startup time is the time after power-up when the modem is ready to begin the
enumeration sequence.
enumeration sequence.
Off mode
Handled by Power
State state machine.
Normal mode
Low power mode
Handled by Power
State state machine.
current_vcc > VOLT_LO_NORM
current_temp <= TEMP_HI_NORM
current_vcc < VOLT_LO_CRIT
current_temp > TEMP_HI_CRIT
current_vcc > VOLT_LO_NORM
current_temp < TEMP_HI_NORM
current_vcc < VOLT_LO_WARN
current_temp > TEMP_HI_WARN
current_vcc < VOLT_HI_NORM
current_temp > TEMP_NORM_LO
current_vcc > VOLT_HI_CRIT
current_temp < TEMP_LO_CRIT
(Manual transition)
Host asserts
W_Disable#
Normal mode
Low supply voltage warning
or
High temperature warning
Enumeration
3.3V
W_Disable#
USB D+
Startup time