MAX17004ETJ+ Maxim Integrated Products, MAX17004ETJ+ Datasheet - Page 28

• Manufacturer Part Number: MAX17004ETJ+
• Description: IC PS CTRLR FOR NOTEBOOKS 32TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17004ETJ+

• Applications: Controller, Notebook Computers
• Voltage - Input: 6 ~ 26 V
• Number Of Outputs: 4
• Voltage - Output: 3.3V, 5V, 2 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
The minimum current-limit threshold must be great
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The
peak inductor current occurs at I
the ripple current; therefore:
where I
old voltage divided by the current-sense resistance
(R
limit threshold is 45mV.
Connect ILIM to LDO5 for a default 50mV current-limit
threshold. In adjustable mode, the current-limit thresh-
old is precisely 1/10th the voltage seen at ILIM. For an
adjustable threshold, connect a resistive divider from
REF to analog ground (GND) with ILIM connected to
the center tap. The external 0.5V to 2V adjustment
range corresponds to a 50mV to 200mV current-limit
threshold. When adjusting the current limit, use 1% tol-
erance resistors and a divider current of approximately
10mA to prevent significant inaccuracy in the current-
limit tolerance.
The current-sense method (Figure 7) and magnitude
determines the achievable current-limit accuracy and
power loss. Typically, higher current-sense limits pro-
vide tighter accuracy, but also dissipate more power.
Most applications employ a current-limit threshold
(V
be determined by:
For the best current-sense accuracy and overcurrent
protection, use a 1% tolerance current-sense resistor
between the inductor and output as shown in Figure
7A. This configuration constantly monitors the inductor
current, allowing accurate current-limit protection.
However, the parasitic inductance of the current-sense
resistor can cause current-limit inaccuracies, especially
when using low-value inductors and current-sense
resistors. This parasitic inductance (L
celed by adding an RC circuit across the sense resistor
with an equivalent time constant:
28
SENSE_
LIMIT
______________________________________________________________________________________
) of 50mV to 100mV, so the sense resistor may
LIMIT_
). For the default setting, the minimum current-
I
LIMIT
R
equals the minimum current-limit thresh-
CS
>
I
LOAD MAX
=
V
I
LIMIT
LIMIT
Setting the Current Limit
(
=
)
+
10
⎛
⎜
⎝
Δ
V
x I
I
ILIM
INDUCTOR
LOAD(MAX)
LIMIT
2
ESL
) can be can-
⎞
⎟
⎠
plus half
Alternatively, high-power applications that do not
require highly accurate current-limit protection may
reduce the overall power dissipation by connecting a
series RC circuit across the inductor (Figure 7B) with
an equivalent time constant:
and:
where R
and R
the typical inductance and R
the inductor manufacturer.
The output filter capacitor must have low enough equiva-
lent series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR to
satisfy stability requirements. The output capacitance
must be high enough to absorb the inductor energy while
transitioning from full-load to no-load conditions without
tripping the overvoltage fault protection. When using high
capacitance, low-ESR capacitors (see stability require-
ments), the filter capacitor’s ESR dominates the output
voltage ripple. So the output capacitor’s size depends on
the maximum ESR required to meet the output voltage
ripple (V
In idle mode, the inductor current becomes discontinu-
ous, with peak currents set by the idle mode current-
sense threshold (V
no-load output ripple may be determined as follows:
DCR
RIPPLE(P-P)
CS
V
is the inductor’s series DC resistance. Use
RIPPLE(P-P)
is the required current-sense resistance,
V
RIPPLE P P
R
R
DCR
CS
C
) specifications:
IDLE
EQ
Output Capacitor Selection
=
( – )
=
R
⎛
⎜
⎝
= R
C
1 =
R
= 0.2V
1
L
EQ
R
ESR
+
=
R
2
R
L
SENSE
⎡
⎢
⎣
V
2
R
ESL
IDLE ESR
I
1
DCR
R
1
LOAD(MAX)
LIMIT
⎞
⎟
⎠
SENSE
R
+
DCR
R
R
1
values provided by
). In idle mode, the
2
⎤
⎥
⎦
LIR