MC34704 FREESCALE [Freescale Semiconductor, Inc], MC34704 Datasheet - Page 16

• Manufacturer Part Number: MC34704
• Description: Multiple Channel DC-DC Power Management IC
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

(PMIC) meant to address power management needs for
various multimedia applications microprocessors in various
configurations with a target overall efficiency of > 80% at
typical loads.
compensation, while REG2, REG4, REG5, and REG7 use
external compensation.
& 8 can be selected through the FREQ pin between 750kHz
and 2.0MHz in 250kHz steps, when operating from a Li-Ion
battery. The high frequency operation is meant to minimize
the size of external components while lower operating
frequencies will allow for higher efficiency. REG7 is limited to
operate at a lower frequency to minimize switching noise
induced by driving the external switching MOSFET, but also
can operate at the 1.0MHz value with proper board layout.
REG 6, 7, and 8 switching frequency can be selected
between 250kHz and 1.0MHz in 250kHz steps through I
mode is implemented to maintain high efficiency. The 34704
uses 4 different phases of switching for all regulators except
REG6, 7, and 8, to spread out the current draw by the
individual converters from the input supply over time, to
reduce the peak input current demand. This allows for better
16
34704
FUNCTIONAL DESCRIPTION
INTRODUCTION
Notes
The 34704 is an multi-channel power management IC
REG1, REG3, REG6, and REG8 use internal
The switching frequency of all regulators except REG6, 7,
For all regulators and at lower loads, a pulse skipping
REGULATOR
17.
18.
REG1
REG6
REG7
REG2
REG3
REG4
REG5
REG8
Synchronous Buck-Boost: These regulators can work as pure BUCK regulator when the output voltage is lower than the input
voltage; and work as pure BOOST regulator when the input voltage is lower than the output voltage. Compensation should be done
for the worst case scenario, which is in most of the cases when the device is working as a boost converter, after compensating for
this scenario it is recommended to verify the buck operation to assure stability in the whole operating range.
Available only on the 34704A
(18)
(18)
(18)
Synchronous Buck-Boost
Synchronous Buck-Boost
Synchronous Buck-Boost
REGULATOR TYPE
Synchronous Boost
Synchronous Boost
Synchronous Boost
Synchronous Buck
Inverter Controller
FUNCTIONAL DESCRIPTION
V
1.2 / 1.5 / 1.8
OUT
2.8 / 3.3
1.8 / 2.5
15.0
15.0
-7.0
5.0
3.3
TYP (V)
INTRODUCTION
2
C.
I
EMI performance and reduction in the input filter
requirements.
resistor divider to set the output voltage. All output voltages
can be adjusted dynamically (Dynamic Voltage Scaling) on
the fly through an I²C serial interface. All converters, except
REG1, utilize automatic soft-start by ramping the reference
voltage to the error amplifier to prevent sudden change in
duty cycle and output current/voltage at power up. REG1
(VG) will limit the inrush current by implementing a peak
current detect and a constant off time.
pin (ONOFF). This pin can be controlled by a mechanical
switch to turn the device on or off. Pressing and releasing the
mechanical switch turns the 34704 on while pressing and
holding the switch for a time period (programmable through
I
granted through I
IC.
OUT
2
C) turns the 34704 off. Enable/disable control is also
(MA)
100
200
150
100
150
The 34704 accepts an input voltage from various sources:
The different channels are:
Each regulator except REG1 uses an external feedback
The 34704 is equipped with a dual function Power On/Off
20
20
15
1 cell Li-Ion/Polymer (2.7V to 4.2V)
5.0V USB supply or AC wall adapter
TYP
I
OUT
2
C for groups of regulators and the whole
(MA)
500
500
550
300
500
60
60
30
MAX
Analog Integrated Circuit Device Data
TARGET APPLICATION
Freescale Semiconductor
Backlight Display
+5V REF
µP Core
µP I/O
µP I/O
REF+
REF -
DDR