MC34704AEP Freescale Semiconductor, MC34704AEP Datasheet - Page 45

• 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

feedback using the standard voltage divider configuration, or
can be programmed to work with a current feedback
configuration to control the current flowing through a LED
string. It does not need external compensation network, thus
the only components that need to be calculated are:
• L: A boost power stage can be designed to operate in
stage is when the input voltage is equal to one half of the
output voltage, which results in the Maximum ÄI
• C
• R1 and RB (for Voltage feedback control): These two
• RS (For current feedback control with LED string):
Analog Integrated Circuit Device Data
Freescale Semiconductor
ESR
L
C
RB
L
CCM for load currents above a certain level usually 5 to
15% of full load. The minimum value of inductor to
maintain CCM can be determined by using the following
procedure:
• Define I
However the worst case condition for the boost power
contribute to its impedance and output voltage ripple are
the ESR, the ESL and the capacitance C. The minimum
capacitor value is approximately:
• Where
• Now calculate
resistors help to set the output voltage to the desire value
using a V
then calculate RB as follows:
This resistor is attached at the end of the LED string and it
min
min
OUT
OUT
15% of full load:
reach the desired.
=
≥
≥
≤
: The three elements of output capacitor that
≥
Vo D
------------------------------------------ -
--------------------- -
----------- -
Vref
Vo T ( )
--------------- -
-------------------------------------------- -
⎛
⎝
16I
Vo
Io
---------------------------- -
-----------------------
1
Fsw Vo
REF
R1
Io
( ) 1
–
max
Δ
OB
OB
D
max
–
VO
2I
Δ
=0.6 V, select R1 between 10k and 100K and
Δ
(
max
D
1
as the minimum current to maintain CCM as
Vo
OB
max
r
–
is the desired output voltage ripple.
r
r
+
Δ
D
I
VO
)
OB
2
T
r
⎞
⎠
the maximum allowed ESR to
[H]
L
[H]
, then:
[F]
[Ω]
[Ω]
voltage in current mode control that is reflected on the FB8
pin.
reverse bias diode is needed from the switching node to the
output in order to cause a drop from the Input to the output,
see
Regulator 7 (Inverter controller - external compensation
needed)
voltage-mode control DC-DC regulator that drive an external
P-MOSFET to supply a typical voltage of -7.0 V at a
maximum current of 60 mA.
• P-MOSFET: The peak current of the MOSFET is assumed
• Diode D7: The peak value of the diode current is I
I
controls the amount of current flowing through it. To
calculate this resistor, set the maximum current you want
to flow though the string and use the following formula:
RS
Where V
When Input voltage is equal to or higher than VOUT8, a
REG7 is a non-synchronous buck/boost inverting PWM
to be I
I
And the voltage rating is given by:
V
which should also be higher than I
current rating should be higher than the output current low
and the repetition reverse voltage V
Q
OB
Figure 9
Q
≥
from 5 to 15% of maximum current rating.
I
=
=
Lpeak
D
Vin
V
--------- -
, which is obtained by the following formula, define
Io
ref
REF
below:
–
=
Figure 9. Reverse Bias Diode
=230 mV is the maximum internal reference
Vo
–
---------------------------- -
(
VOUT8
Io
1
SW8
BT8
FB8
–
+
D
I
OB
FUNCTIONAL DEVICE OPERATION
)
CBOOT
D8
COMPONENT CALCULATION
RB
R1
L8
Lpeak
RRM
VOUT8
. The average
VIN
is given by:
[Ω]
FSM
34704
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