MAX8744ETJ+ Maxim Integrated Products, MAX8744ETJ+ Datasheet - Page 17

• 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

Table 2. Component Suppliers
The MAX8744/MAX8745 standard application circuit
(Figure 1) generates the 5V/5A and 3.3V/5A typical of the
main supplies in a notebook computer. The input supply
range is 7V to 24V. See Table 1 for component selec-
tions, while Table 2 lists the component manufacturers.
The MAX8744/MAX8745 contain two interleaved, fixed-
frequency, step-down controllers designed for low-volt-
age power supplies. The optimal interleaved architecture
guarantees out-of-phase operation, reducing the input
capacitor ripple. One internal LDO generates the keep-
alive 5V power. The MAX8744/MAX8745 have an auxil-
iary LDO with an adjustable output for generating either
the 3.3V keep-alive supply or regulating the low-power
12V system supply.
An internal linear regulator produces a preset 5V low-
current output. LDO5 powers the gate drivers for the
external MOSFETs, and provides the bias supply
required for the SMPS analog controller, reference, and
logic blocks. LDO5 supplies at least 100mA for exter-
nal and internal loads, including the MOSFET gate
drive, which typically varies from 5mA to 50mA,
depending on the switching frequency and external
MOSFETs selected. Bypass LDO5 with a 4.7µF or
greater ceramic capacitor (1µF per 25mA of load) to
guarantee stability under the full-load conditions.
AVX
Central Semiconductor
Fairchild
International Rectifier
KEMET
NEC/Tokin
Panasonic
Philips
Pulse
Renesas
SANYO
Sumida
Taiyo Yuden
TDK
TOKO
Vishay (Dale, Siliconix)
SUPPLIER
Supply Controllers for Notebook Computers
Fixed 5V Linear Regulator (LDO5)
High-Efficiency, Quad-Output, Main Power-
______________________________________________________________________________________
Detailed Description
www.avx.com
www.centralsemi.com
www.fairchildsemi.com
www.irf.com
www.kemet.com
www.nec-tokin.com
www.panasonic.com/industrial
www.philips.com
www.pulseeng.com
www.renesas.com
www.edc.sanyo.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.tokoam.com
www.vishay.com
WEBSITE
The MAX8744/MAX8745 switch-mode power supplies
(SMPS) require a 5V bias supply in addition to the high-
power input supply (battery or AC adapter). This 5V bias
supply is generated by the controller’s internal 5V linear
regulator (LDO5). This bootstrapped LDO allows the
controller to power up independently. The gate-driver
input supply is connected to the fixed 5V linear-regulator
output (LDO5). Therefore, the 5V LDO supply must pro-
vide LDO5 (PWM controller) and the gate-drive power,
so the maximum supply current required is:
where I
and Q
sheet’s total gate-charge specification limits at V
When the 5V main output voltage is above the LDO5
bootstrap-switchover threshold and has completed
soft-start, an internal 1Ω (typ) p-channel MOSFET
shorts CSL5 to LDO5, while simultaneously shutting
down the LDO5 linear regulator. This bootstraps the
device, powering the internal circuitry and external
loads from the 5V SMPS output (CSL5), rather than
through the linear regulator from the battery. Boot-
strapping reduces power dissipation due to gate
charge and quiescent losses by providing power from
a 90%-efficient switch-mode source, rather than from a
much-less-efficient linear regulator. The current capa-
bility increases from 100mA to 200mA when the LDO5
output is switched over to CSL5. When ON5 is pulled
low, the controller immediately disables the bootstrap
switch and reenables the 5V LDO.
The 2V reference is accurate to ±1% over temperature
and load, making REF useful as a precision system ref-
erence. Bypass REF to GND with a 0.1µF or greater
ceramic capacitor. The reference sources up to 50µA
and sinks 5µA to support external loads. If highly accu-
rate specifications are required for the main SMPS out-
put voltages, the reference should not be loaded.
Loading the reference reduces the LDO5, CSL5
(OUT5), CSL3 (OUT3), and OUTA output voltages
slightly because of the reference load-regulation error.
Drive SHDN below the precise SHDN input falling-edge
trip level to place the MAX8744/MAX8745 in its low-
power shutdown state. The controller consumes only
8µA of quiescent current while in shutdown mode.
When shutdown mode activates, the reference turns off
after the controller completes the shutdown sequence
G(LOW)
CC
I
BIAS
is 0.7mA (typ), f
System Enable/Shutdown ( SHDN )
= I
= 5mA to 50mA (typ)
and Q
CC
SMPS to LDO Bootstrap Switchover
+ f
G(HIGH)
SW
SW
(Q
G(LOW)
is the switching frequency,
are the MOSFET data
Reference (REF)
+ Q
G(HIGH)
GS
)
= 5V.
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