MAX5081 Maxim Integrated Products, MAX5081 Datasheet - Page 15

• Manufacturer Part Number: MAX5081
• Description: 1A / 40V / MAXPower Step-Down DC-DC Converters
• Manufacturer: Maxim Integrated Products

Figure 4. Error Amplifier Compensation Circuit (Closed-Loop
and Error Amplifier Gain Plot) for Higher ESR Output Capacitors
Since R3 >> R6, R3 + R6 can be approximated as R3.
R3 is then calculated as:
f
The MAX5080/MAX5081 is available in a thermally
enhanced package and can dissipate up to 2.7W at T
= +70°C. When the die temperature reaches +160°C,
the part shuts down and is allowed to cool. After the
parts cool by 20°C, the device restarts with a soft-start.
P3
is set at 5xf
GAIN
(dB)
V
OUT
C
C
C6
8
. Therefore, C8 is calculated as:
=
R3
R
______________________________________________________________________________________
3
(
R4
R6
f
2
Z1
≈
π
f
2
Z2
×
π
C
REF
CLOSED-LOOP
GAIN
×
7
f
LC
×
C
1
R5
R
7
f
P2
EA
×
5
C8
Power Dissipation
C
×
f
C
6
f
P3
C7
f
P3
−
1
)
1A, 40V, MAXPower Step-Down
FREQUENCY
COMP
EA
GAIN
A
The power dissipated in the device is the sum of the
power dissipated from supply current (P
losses due to switching the internal power MOSFET
(P
rent through the internal power MOSFET (P
The total power dissipated in the package must be lim-
ited such that the junction temperature does not
exceed its absolute maximum rating of +150°C at maxi-
mum ambient temperature. Calculate the power lost in
the MAX5080/MAX5081 using the following equations:
The power loss through the switch:
R
(see Electrical Characteristics).
The power loss due to switching the internal MOSFET:
where t
power MOSFET measured at LX.
The power loss due to the switching supply current
(I
The total power dissipated in the device will be:
TRANSISTOR COUNT: 4300
PROCESS: BiCMOS/DMOS
SW
ON
I
SW
RMS MOSFET
):
), and the power dissipated due to the RMS cur-
is the on-resistance of the internal power MOSFET
_
R
and t
P
P
MOSFET
SW
P
P
DC-DC Converters
MOSFET
TOTAL
F
=
=
are the rise and fall times of the internal
I
I
PK
DC
V
IN
=
⎡
⎣ ⎢
= P
I
P
=
=
2
I
= I
RMS MOSFET
×
Q
PK
I
I
OUT
OUT
MOSFET
I
RMS_MOSFET
= V
OUT
+
_
(
IN
I
+
−
PK
Chip Information
×
∆
∆
x I
4
(
I
I
P P
P P
t
×
2
+ P
2
R
SW
−
−
I
DC
www.DataSheet4U.com
2
×
SW
t
2
x R
F
)
)
x R
+
+ P
×
ON
I
2
f
ON
DC
SW
Q
Q
), transition
⎤
⎦ ⎥
×
MOSFET
D
3
15
).