max5073atit Maxim Integrated Products, Inc., max5073atit Datasheet - Page 18

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

2.2MHz, Dual-Output Buck or Boost Converter
with Internal Power MOSFETs
The input current for the boost converter is continuous
and the RMS ripple current at the input is low. Calculate
the capacitor value and ESR of the input capacitor
using the following equations.
where
where V
MOSFET plus the voltage drop across the inductor
ESR. ∆I
calculated above. ∆V
to the capacitor discharge and ∆V
tion due to ESR of the capacitor.
For the boost converter, the output capacitor supplies
the load current when the main switch is ON. The
required output capacitance is high, especially at high-
er duty cycles. Also, the output capacitor ESR needs to
be low enough to minimize the voltage drop due to the
ESR while supporting the load current. Use the follow-
ing equation to calculate the output capacitor for a
specified output ripple tolerance.
I
due to the capacitor discharge and ∆V
bution due to the ESR of the capacitor. D
maximum duty cycle at minimum input voltage.
The MAX5073 includes a high-frequency, low R
switching MOSFET. At +85°C, the R
nal switch for converter 1 and converter 2 are 290mΩ
and 630mΩ, respectively. The DC loss is a function of
the RMS current in the switch while the switching loss is
a function of switching frequency and input voltage. Use
18
O
is the load current, ∆V
______________________________________________________________________________________
L
DS
is the peak-to-peak inductor ripple current as
is the total voltage drop across the internal
C
∆I
IN
C
L
OUT
ESR
=
=
Q
ESR
4
(
is the portion of input ripple due
V
IN
=
×
=
Q
L
=
∆
I
∆
−
O
∆
f
I
V
SW
L
is the portion of the ripple
×
∆
V
V
∆
Q
DS
V
×
ESR
I
I
×
ESR
O
L
f
SW
×
D
×
)
D
MAX
×
f
ESR
SW
∆
Power Dissipation
DS_ON
V
Output Capacitor
D
Q
Input Capacitor
ESR
is the contribu-
is the contri-
of the inter-
MAX
DS_ON
is the
the following equations to calculate the RMS current,
DC loss, and switching loss of each converter. The
MAX5073 device is available in a thermally enhanced
package and can dissipate up to 2.7W at +70°C ambient
temperature. The total power dissipation in the package
must be limited so the junction temperature does
not exceed its absolute maximum rating of +150°C at
maximum ambient temperature.
For the buck converter:
where
See the Electrical Characteristics table for the
R
For the boost converter:
DS(ON)MAX
I
RMS
I
RMS
P
SW
=
value.
=
P
DC
(
=
(
I
2
I
2
DC
V
∆I
DC
=
INMAX
I
L
DC
I
+I
2
I
I
+I
I
I
PK
IN
=
DC
PK
RMS
2
=
(
2
PK
=
V
PK
=
I
=
=
O
IN
×
V
V
I
×
I
O
I
+(I
IN
IN
IN
O
L
−
+(I
I
−
R
O
+
×
×
+
DS(ON)MAX
∆
V
−
DC
× η
2
DC
DS
I
∆
I
×
f
L
O
∆
SW
2
∆
I
4
2
2
L
I
(
I
×
L
L
t
)
×
R
I
PK
I
×
PK
+
D
))
))
t
F
×
×
)
D
D
×
MAX
MAX
3
f
3
SW