MC34704AEP Freescale Semiconductor, MC34704AEP Datasheet - Page 30

• Manufacturer Part Number: MC34704AEP
• Description: IC POWER MANAGEMENT 56-QFN
• Manufacturer: Freescale Semiconductor

Specifications of MC34704AEP

• Applications: Processor
• Current - Supply: 86mA
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 56-QFN
• Output Voltage: 5 V
• Input Voltage: 2.7 V to 5.5 V
• Switching Frequency: 750 KHz to 2 MHz
• Mounting Style: SMD/SMT
• Number Of Outputs: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RST OUTPUT SIGNAL PIN
output that should be connected to the reset input of the
microprocessor. An external pull up resistor should be
connected to this output and is recommended to be pulled up
to V2 for best performance (If this pin is pulled up to the VIN
pin, then the 1.0 µA shutdown current budget is not
guaranteed)
processor in “reset”. When VG, REG2, REG3, and REG4 are
all in regulation (both OV and UV flags for each regulator are
de-asserted) and no faults exist, the RST output is de-
asserted after a 10 ms delay to take the processor out of
reset. Then the processor can go through its own internal
power up sequence and can start communicating to the rest
of the system.
faults: over-temperature, short-circuit, over-current for more
than 10 ms, over-voltage in response A, under-voltage in
response A, or is shutting down normally, the RST output is
asserted to put the processor back in reset. If ANY of the
above four regulators has an over-voltage response B fault or
an under-voltage response B fault, the RST output will not be
asserted (only the OV and UV flags will be available for the
microprocessor to read).
THERMAL LIMIT DETECTION
It uses an external MOSFET.
CURRENT LIMIT MONITORING
• A soft over-current limit (over-current limit): If the peak
30
34704
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
• Do nothing until the second time period expires and let
This is a power reset output signal. It is an open drain
At power up, the RST pin is asserted (low) to keep the
If ANY of the above four regulators has any of the following
There is a thermal sensor for each regulator except REG7.
The current limit circuitry has two levels of current limiting:
current reaches the typical over-current limit, the switcher
will start a cycle-by-cycle operation to limit the current and
the device power off by itself
During this time, the processor can abort the shutdown
process or shutdown immediately before the 2nd period
elapses with an I
1
0
Turn On
2
C command
Figure 6. Hardware Power Up/Down Timing
Shutdown Delay
Programmable
1
st
1
st
Period
Period
Shutdown Flag Asserted
edge. It is normally pulled high.
• A hard over-current limit (short circuit limit) that is higher
OUTPUT OVER-VOLTAGE/UNDER-VOLTAGE
MONITORING
user has two options that can be programmed through the
I
the 34704 would alert the processor through I
event happened.
34704 communicates to the processor that an over-voltage/
under-voltage condition has occurred and wait for the
2
C interface:
The ONOFF pin is edge sensitive and activates on a falling
a 10 ms current limit timer starts. The switcher will stay in
this mode of operation until one of the following occurs:
• The current is reduced back to the normal level inside
• The output reaches the thermal shutdown limit and
• The current limit timer expires without gaining normal
• The output current keeps increasing until it reaches the
than the cycle by cycle limit at which the device reacts by
shutting down the output immediately. This is necessary to
prevent damage in case of a short-circuit. After that, only
GrpB will attempt a one time retry after a timeout period of
10ms and will go through a new soft start cycle
In the case of an output over-voltage/under-voltage, the
Response A: The output will switch off automatically and
Response B: The output will not switch off. Rather the
ON/OFF Pin can be released during this
period without affecting the device response process
the 10 ms timer and in this case normal operation is
gained back
turns off
operation at which point the output turns off. Then only
for GrpB, at the end of a timeout period of 10 ms, the
output will attempt to restart again but for one time only.
second over-current limit, see below for more details
2
Shutdown Delay
Programmable
nd
2
Period
st
Period
Shutdown if No Processor Communication
Analog Integrated Circuit Device Data
Freescale Semiconductor
2
C that such an