MAX1901ETJ+ Maxim Integrated Products, MAX1901ETJ+ Datasheet - Page 21

• Manufacturer Part Number: MAX1901ETJ+
• Description: IC CNTRLR PWR SPLY LN 32-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1901ETJ+

• Applications: Controller, Notebook Computers
• Voltage - Input: 4.2 ~ 30 V
• Number Of Outputs: 4
• Voltage - Output: 2.5 ~ 5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Output Voltage: 3.3 V, 5 V, 2.5 V to 5.5 V
• Output Current: 5 A
• Input Voltage: 4.2 V to 30 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

connected but no battery is installed. V
exceed 30V.
Minimum Input (Battery) Voltage, V
be taken at full load under the lowest battery condi-
tions. If V
cuit to externally hold V
lockout threshold. If the minimum input-output differ-
ence is less than 1.5V, the filter capacitance required to
maintain good AC load regulation increases (see the
Low-Voltage Operation section).
The exact inductor value isn’t critical and can be freely
adjusted to make trade-offs between size, cost, and
efficiency. Lower inductor values minimize size and
cost, but reduce efficiency due to higher peak-current
levels. The smallest inductor is achieved by lowering
the inductance until the circuit operates at the border
between continuous and discontinuous mode. Further
reducing the inductor value below this crossover point
results in discontinuous-conduction operation even at
full load. This helps lower output-filter capacitance
requirements, but efficiency suffers due to high I
losses. On the other hand, higher inductor values mean
greater efficiency, but resistive losses due to extra wire
turns will eventually exceed the benefit gained from
lower peak-current levels. Also, high inductor values
can affect load-transient response (see the V
tion in the Low-Voltage Operation section). The equa-
tions that follow are for continuous-conduction
operation, since the MAX1901/MAX1902/MAX1904 are
intended mainly for high-efficiency, battery-powered
applications. Discontinuous conduction doesn’t affect
normal idle-mode operation.
Three key inductor parameters must be specified:
inductance value (L), peak current (I
resistance (R
constant (LIR) which is the ratio of inductor peak-to-
peak AC current to DC load current. A higher LIR value
allows smaller inductance, but results in higher losses
and higher ripple. A good compromise between size
and losses is found at a 30% ripple-current to load-cur-
rent ratio (LIR = 0.3), which corresponds to a peak-
inductor current 1.15 times higher than the DC load
current.
where:
500kHz Multi-Output, Low-Noise Power-Supply
IN(MIN)
f = switching frequency, normally 333kHz or
I
OUT
L
500kHz
=
DC
= maximum DC load current
V
IN MAX
V
). The following equation includes a
is less than 4.2V, use an external cir-
OUT
(
______________________________________________________________________________________
(
V
)
IN MAX
× ×
(
L
f I
above the V
Controllers for Notebook Computers
OUT
)
-
V
OUT
×
LIR
)
Inductor Value
IN(MIN)
IN(MAX)
PEAK
L
undervoltage
.This should
), and DC
SAG
must not
equa-
2
R
The nominal peak-inductor current at full load is 1.15
I
current can be calculated by:
The inductor’s DC resistance should be low enough that
R
ciency performance. If a standard off-the-shelf inductor is
not available, choose a core with an LI
than L
that fits the winding area. Ferrite core material is strongly
preferred. Shielded-core geometries help keep noise,
EMI, and switching-waveform jitter low.
The current-sense resistor value is calculated accord-
ing to the worst-case low current-limit threshold voltage
(from the Electrical Characteristics) and the peak
inductor current:
Use I
Value section.
Use the calculated value of R
FET switches and specify inductor saturation-current
ratings according to the worst-case high current-limit
threshold voltage:
Low-inductance resistors, such as surface-mount
metal-film, are recommended.
The input filter capacitor is usually selected according
to input ripple current requirements and voltage rating,
rather than capacitor value. Ceramic capacitors or
Sanyo OS-CON capacitors are typically used to handle
the power-up surge-currents, especially when connect-
ing to robust AC adapters or low-impedance batteries.
RMS input ripple current (I
input voltage and load current, with the worst case
occurring at V
OUT
DC
✕
if the above equation is used; otherwise, the peak
PEAK
I
✕
PEAK
I
PEAK
I
PEAK
LIR = ratio of AC to DC inductor current, typi-
from the second equation in the Inductor
=
< 100mV, as it is a key parameter for effi-
IN
2
I
LOAD
and wind it with the largest-diameter wire
I
PEAK MAX
cally 0.3; should be >0.15
= 2
Current-Sense Resistor Value
R
+
SENSE
✕
(
(
V
V
2
OUT
OUT
× × ×
)
=
f L V
=
(
Input-Capacitor Value
:
RMS
V
I
80
R
IN MAX
PEAK
120
SENSE
(
SENSE
mV
) is determined by the
mV
IN MAX
)
-
(
V
OUT
to size the MOS-
)
2
)
rating greater
21
✕