MC34704AEP Freescale Semiconductor, MC34704AEP Datasheet - Page 20

• 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

INTERNAL BIAS CIRCUIT
Gate Driver Voltage (VG)
used to supply internal circuitry and voltage biases through
the VG output. It also provides the gate drive voltage for the
rest of the regulators and itself.
how REG1 is a critical part of powering up the 34704. Based
on this, REG1 will need extra circuitry to help it boot up until
its output voltage is high enough that it can supply internal
circuitry for the main control loop to take over.
REG1 VG output starts rising. When the appropriate internal
circuitry is alive and the switching frequency F
selected, the PWM control of REG1 can take over.
VREF Generator - Internal Reference
is controlled by the I
voltage for setting the output voltage on each regulator.
20
34704
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
REG1/VG is the main regulator of the 34704 IC and will be
See Power-Up Sequence on page 28
REG1 VG starts up in peak current detect PFM mode and
Each one of the regulators in the 34704 uses a DAC which
2
C interface to generate a dynamic VREF
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Figure 4. MC34704 Functional Internal Block Diagram
for more details on
SW1
is
VDDI Reference Voltage
precise low current 2.5 V voltage that is meant to serve as
reference voltage to derive the FREQ and SS voltage needed
to set the switching frequency 1 (FSW1) and the soft start,
respectively.
FAULT DETECTION AND PROTECTION
Thermal Limit Detection
All regulators of the corresponding group will shutdown if at
least one of them reaches the thermal limit. If either REG2,
REG3 or REG4 reaches its thermal limit, the whole part will
shutdown immediately.
Over-Current & Short Circuit Monitoring
• A soft over-current limit (over-current limit): If the peak
The 34704 uses the internal VG voltage to provide a
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
a 10 ms current limit timer starts. The switcher will stay in
this mode of operation until the part regains normal
Analog Integrated Circuit Device Data
*
Freescale Semiconductor