MC33394DH Freescale Semiconductor, MC33394DH Datasheet - Page 27

• Manufacturer Part Number: MC33394DH
• Description: IC POWER SUPPLY MULT-OUT 44-HSOP
• Manufacturer: Freescale Semiconductor

Specifications of MC33394DH

• Applications: Motorola MPC55x, MPC56x Microprocessors
• Interface: SPI Serial
• Voltage - Supply: 4 V ~ 26.5 V
• Package / Case: 44-BSOP (0.433", 11.00mm Width) Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Boost Mode
parts, when the power switch is on and off. When the power
switch turns on, the input voltage source is placed directly
across the inductor, and the current ramps up linearly
through the inductor as described by:
Where:
t on is the on–time of the power switch.
V in is the input voltage.
i L(on) is the inductor current during the on–time.
L is the inductance of the inductor L.
within the core material. In order to maintain steady–state
operation, the amount of energy stored during each switching
cycle, times the frequency of operation must be higher (to
cover the losses) than the power demands of the load:
flies back above the input voltage and is clamped by the
forward biased rectifier at the output voltage.
until the new on time begins or, in case of discontinuous
mode of operation, until the energy stored in the inductor core
drops to zero.
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
The operation of the boost converter also consists of two
The current ramping across the inductor stores energy
When the power switch turns off again, the inductor voltage
The current ramps down through the inductor to the output
V D(fwd)
V in
V in
P sto
POWER SWITCH OFF
POWER SWITCH ON
i L(on)
+
I Q
Q
L
1
2
LI
+
D
2
I LO
pk
Figure 13. Basic Buck Converter Operation and its Waveforms
V in
I LO
I D
Freescale Semiconductor, Inc.
L
f
I L
L
C O
C O
u
+
+
t on
For More Information On This Product,
P out
+
C O
V out
V out
I LOAD
I LOAD
+
–
Go to: www.freescale.com
+
+
–
–
V O
R LOAD
R LOAD
R LOAD
33394
Where:
t off is the off–time of the power switch.
V o is the output voltage.
During the steady state operation i L(on) = i L(off) = I L , and
Where:
d is the duty cycle, and d = t on /T.
T is switching period, T = 1/f.
f is the frequency of operation.
as:
Where:
V ppCo is the ripple caused by output current.
of the output capacitor is:
The ripple voltage of the boost converter can be described
The portion of the output ripple voltage caused by the ESR
V Co
–I D
V D
I Q
I L
t on
Vpp ESR
T
V fwd
t off
Vpp Co
i L(off)
+
D
(I o
d
I L
+
+
+
(V o
C o
I o
V o
V in
V o
*
*
V o
)
V in )
(V o
V in
L
1
2
V o
D
*
I L )
V in )
t off
f
R ESR
t
I O
27