MAX1534ETE+T Maxim Integrated Products, MAX1534ETE+T Datasheet - Page 12

• Manufacturer Part Number: MAX1534ETE+T
• Description: IC PWR SUPPLY CONTROLLER 16TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1534ETE+T

• Applications: Power Supply Controller
• Voltage - Input: 4.5 ~ 24 V
• Current - Supply: 15µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

ous operation, do not exceed the absolute maximum
junction temperature rating of T
The MAX1534’s maximum power dissipation depends
on the thermal resistance of the case and circuit board,
the temperature difference between the die junction
and ambient air, and the rate of air flow. The power dis-
sipated in the device is the sum of the buck MOSFET
switching and conduction losses and the linear regula-
tors’ conduction losses. The maximum power dissipa-
tion is:
where T
MAX1534 die junction and the surrounding air, θ
θ
the thermal resistance through the printed circuit board,
copper traces, and other materials to the surrounding
air. The exposed backside pad of the MAX1534 pro-
vides a low thermal impedance to channel heat out of
the package. Connect the exposed backside pad to
ground using a large pad or ground plane.
The MAX1534 features dual mode operation; it oper-
ates in either a preset voltage mode (see Table 4) or an
adjustable mode. In preset voltage mode, internal
trimmed feedback resistors set the MAX1534 outputs to
3.3V for V
regulator). Select this mode by connecting PRESET to
ground. Connect PRESET to IN to operate the
MAX1534 in the adjustable mode. Select an output volt-
age using two external resistors connected as a volt-
age-divider to FB_ (Figure 4). The output voltage is set
by the following equation:
where V
1.0V to V
To simplify resistor selection:
Choose R
tion, accuracy, and high-frequency power-supply rejec-
tion. The total current through the external resistive
feedback and load resistors should not be less than
10µA. Since the V
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
12
JC
Operating Region and Power Dissipation
) is the thermal resistance of the package, and θ
______________________________________________________________________________________
Preset and Adjustable Output Voltages
J
FB_
LDOIN
- T
OUT1
BOT_
A
= 1.0V, V
P
R
MAX
is the temperature difference between the
TOP
V
, 1.8V for V
, and V
OUT
= 100kΩ to optimize power consump-
_
= (T
FB_
_
=
=
R
OUT1
OUT3
J
BOT
tolerance is typically less than
V
- T
FB
OUT2
A
_
_
and V
can range from 1.0V to V
) / (θ






1
V
+
V
, and 5.0V for FB3 (buck
J
OUT
FB
R
R
= +150°C.
JB
TOP
BOT
OUT2
_
_
+ θ
−
_
_
 1
BA





can range from
)
( PRESET )
JB
BA
(or
IN
is
.
±15mV, the output can be set using fixed resistors
instead of trim pots.
When selecting the inductor, consider these four para-
meters: inductance value, saturation rating, series
resistance, and size. The MAX1534 operates with a
wide range of inductance values. For most applica-
tions, values between 10µH and 50µH work best with
the controller’s high switching frequency. Larger induc-
tor values reduce the switching frequency and thereby
improve efficiency and EMI. The trade-off for improved
efficiency is a higher output ripple and slower transient
response. On the other hand, low-value inductors
respond faster to transients, improve output ripple, offer
smaller physical size, and minimize cost. If the inductor
value is too small, the peak inductor current exceeds
the current limit due to current-sense comparator prop-
agation delay, potentially exceeding the inductor’s cur-
rent rating. Calculate the minimum inductance value as
follows:
where t
The inductor’s saturation current rating must be greater
than the peak switch current limit, plus the overshoot
due to the 150ns current-sense comparator propaga-
tion delay. Saturation occurs when the inductor’s mag-
netic flux density reaches the maximum level the core
can support and the inductance starts to fall. Choose
an inductor with a saturation rating greater than I
in the following equation:
Inductor series resistance affects both efficiency and
dropout voltage (see the Buck Dropout Performance
section).
High series resistance limits the maximum current avail-
able at lower input voltages, and increases the dropout
Table 4. PRESET Setting
PRESET
GND
IN
I
PEAK
ON(MIN)
L
(
= I
MIN
LX(PEAK)
)
= 0.5µs.
Adjustable
=
MODE
Preset
(
V
IN MAX
(
+ (V
)
Design Procedure
IN
I
- V
LX PEAK
- V
OUT3
(
OUT1 = 3.3V, FB1 = GND,
OUT2 = 1.8V, FB2 = GND,
OUT3
FB_ regulates to 1.0V
OUT3 = FB3 = 5.0V
Buck Converter
)
Inductor Selection
OUT_ AND FB_
)
×
)
t
ON MIN
✕
150ns / L
(
)
PEAK