MAX8744ETJ+ Maxim Integrated Products, MAX8744ETJ+ Datasheet - Page 30

• Manufacturer Part Number: MAX8744ETJ+
• Description: IC CNTRLR PWR SUP QUAD 32TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8744ETJ+

• Applications: Controller, Notebook Computers
• Voltage - Input: 6 ~ 26 V
• Number Of Outputs: 4
• Voltage - Output: 3.3V, 5V, 1 ~ 26 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Duty Cycle (max): 99 %
• Output Voltage: 3.315 V, 5.015 V, 2 V to 5.5 V
• Mounting Style: SMD/SMT
• Switching Frequency: 200 KHz, 300 KHz, 500 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Boost, Flyback, Forward
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The 40/60 optimal interleaved architecture of the
MAX8744/MAX8745 allows the input voltage to go as
low 8.3V before the duty cycles begin to overlap. This
offers improved efficiency over a regular 180° out-of-
phase architecture where the duty cycles begin to
overlap below 10V. Figure 8 shows the input-capacitor
RMS current vs. input voltage for an application that
requires 5V/5A and 3.3V/5A. This shows the improve-
ment of the 40/60 optimal interleaving over 50/50 inter-
leaving and in-phase operation.
For most applications, nontantalum chemistries (ceram-
ic, aluminum, or OS-CON) are preferred due to their
resistance to power-up surge currents typical of sys-
tems with a mechanical switch or connector in series
with the input. Choose a capacitor that has less than
10°C temperature rise at the RMS input current for opti-
mal reliability and lifetime.
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
Figure 8. Input RMS Current
30
INPUT RMS CURRENT FOR INTERLEAVED OPERATION:
INPUT RMS CURRENT FOR SINGLE-PHASE OPERATION:
______________________________________________________________________________________
I
I
I
D
IN
RMS
RMS
LX
=
5
V
=
=
=
OUT OUT
I
V
LOAD
(
OUT
V
OUT
5
IN
I
5
5
⎛
⎜
⎜
⎜
⎝
5
−
V
V
I
+
IN IN
IN
OUT IN
D
V
)
LX
2
OUT OUT
(
(
3
D
V
V
LX
=
3
IN
I
V
5
−
OUT
V
−
IN
V
3
OUT
D
3
OL
)
)
⎞
⎟
⎟
⎟
⎠
D
+
OL
(
I
OUT
=
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
DUTY CYCLE OVERLAP FRACTION
0
3
−
6
I
IN
INPUT CAPACITOR RMS CURRENT
50/50 INTERLEAVING
)
−
2
8
(
D
LX
vs. INPUT VOLTAGE
10
IN PHASE
3
40/60 OPTIMAL
INTERLEAVING
−
12
D
V
IN
OL
(V)
)
14
Most of the following MOSFET guidelines focus on the
challenge of obtaining high load-current capability
when using high-voltage (> 20V) AC adapters. Low-
current applications usually require less attention.
The high-side MOSFET (N
the resistive losses plus the switching losses at both
V
should be roughly equal to the losses at V
lower losses in between. If the losses at V
significantly higher, consider increasing the size of N
Conversely, if the losses at V
higher, consider reducing the size of N
vary over a wide range, maximum efficiency is achieved
by selecting a high-side MOSFET (N
tion losses equal to the switching losses.
+
IN(MIN)
(
I
OUT
16
5
18
+
and V
I
OUT
20
3
IN(MAX)
−
I
IN
)
2
D
Power-MOSFET Selection
OL
. Ideally, the losses at V
+
H
I
IN
) must be able to dissipate
2
(
IN(MAX)
1
−
D
LX
H
5
) that has conduc-
H
−
are significantly
. If V
D
LX
IN(MAX)
3
IN
IN(MIN)
+
does not
D
OL
IN(MIN)
, with
)
are
H
.