max5073atit Maxim Integrated Products, Inc., max5073atit Datasheet - Page 19

• Manufacturer Part Number: max5073atit
• Description: Max5073 2.2mhz, Dual-output Buck Or Boost Converter With Internal Power Mosfets
• Manufacturer: Maxim Integrated Products, Inc.

where V
the Electrical Characteristics for the R
where t
MOSFET. The t
measured in the actual application.
The supply current in the MAX5073 is dependent on
the switching frequency. See the Typical Operating
Characteristics to find the supply current of the
MAX5073 at a given operating frequency. The power
dissipation (P
is calculated using following equation.
The total power dissipation P
where P
converter 2, respectively. P
losses in converter 1 and converter 2.
Calculate the temperature rise of the die using the
following equation:
where, θ
the package equal to +2°C/W. Solder the exposed pad of
the package to a large copper area to minimize the case-
to-ambient thermal impedance. Measure the temperature
of the copper area near the device at a worst-case condi-
tion of power dissipation and use +2°C/W as θ
impedance. The case-to-ambient thermal impedance
(θ
from the PC board to the ambient. Use a large copper
area to keep the PC board temperature low. The θ
usually in the +20°C/W to +40°C/W range .
The MAX5073 provides an internal transconductance
amplifier with its inverting input and its output available
to the user for external frequency compensation. The
flexibility of external compensation for each converter
offers wide selection of output filtering components,
especially the output capacitor. For cost-sensitive
applications, use high-ESR aluminum electrolytic
capacitors; for component size-sensitive applications,
use low-ESR tantalum or ceramic capacitors at the out-
C-A
2.2MHz, Dual-Output Buck or Boost Converter
) is dependent on how well the heat is transferred
R
P
DC1
DS
JC
T
and t
P
= P
is the drop across the internal MOSFET. See
is the junction-to-case thermal impedance of
SW
and P
S
DC1
) in the device due to supply current (I
F
R
P
=
P
DC
S
are rise and fall times of the internal
and t
V
T
DC2
______________________________________________________________________________________
O
+ P
J
=
=
= T
V
×
I
INMAX
2
DC2
F
I
are DC losses in converter 1 and
IN
RMS
C
are typically 20ns, and can be
×
+ (P
+ P
SW1
(
×
t
T
R
4
×
R
T
in the device is:
SW1
I
DS(ON)MAX
+
SUPPLY
and P
x θ
t
F
JC
)
+ P
×
Compensation
)
DS(ON)MAX
SW2
f
SW
SW2
are switching
+ P
with Internal Power MOSFETs
JC
S
thermal
value.
C-A
S
is
)
put. The high switching frequency of MAX5073 allows
use of ceramic capacitors at the output.
Choose all the passive power components that meet
the output ripple, component size, and component cost
requirements. Choose the small-signal components for
the error amplifier to achieve the desired closed-loop
bandwidth and phase margin. Use a simple pole-zero
pair (Type II) compensation if the output capacitor ESR
zero frequency is below the unity-gain crossover fre-
quency (f
the ESR zero frequency is higher than f
pensating for a continuous mode boost converter that
has a right-half-plane zero.
Use the following procedure 1 to calculate the compen-
sation network components when f
Procedure 1 (See Figure 6)
1) Calculate the f
2) Calculate the unity-gain crossover frequency as:
If the f
Type II compensation network where R
midband zero f
quency pole.
3) Calculate modulator gain G
Figure 6. Type II Compensation Network
quency.
ZERO,ESR
C
). Type III compensation is necessary when
f
f
ZERO ESR
LC
mid,zero
R
R
is lower than f
1
2
=
ZERO,ESR
V
2
OUT
,
π
V
f
×
C
REF
Buck Converter Compensation
, and R
=
=
L
OUT
f
-
+
2
SW
20
g
and LC double pole:
M
π
1
C
R
×
F
F
F
C
×
C
M
ESR
and close to f
C
CF
at the crossover fre-
OUT
ZERO,ESR
1
provides a high-fre-
×
COMP
C
C
CF
C
F
OUT
C
or when com-
F
< f
provides a
LC
C
.
, use a
19