MAX17007EVKIT+ Maxim Integrated Products, MAX17007EVKIT+ Datasheet - Page 30

• Manufacturer Part Number: MAX17007EVKIT+
• Description: KIT EVAL FOR MAX17007
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17007EVKIT+

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.2V, 1.5V
• Current - Output: 12A, 12A
• Voltage - Input: 7 ~ 24V
• Regulator Topology: Buck
• Frequency - Switching: 270kHz, 330kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MAX17007
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The output filter capacitor must have low enough effec-
tive series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR
to satisfy stability requirements.
In core and chipset converters and other applications
where the output is subject to large-load transients, the
output capacitor’s size typically depends on how much
ESR is needed to prevent the output from dipping too
low under a load transient. Ignoring the sag due to
finite capacitance:
In low-power applications, the output capacitor’s size
often depends on how much ESR is needed to maintain
an acceptable level of output ripple voltage. The output
ripple voltage of a step-down controller equals the total
inductor ripple current multiplied by the output capacitor’s
ESR. The maximum ESR to meet ripple requirements is:
where f
With most chemistries (polymer, tantalum, aluminum,
electrolytic), the actual capacitance value required
relates to the physical size needed to achieve low ESR
and the chemistry limits of the selected capacitor tech-
nology. Ceramic capacitors provide low ESR, but the
capacitance and voltage rating (after derating) are
determined by the capacity needed to prevent V
and V
sients. Generally, once enough capacitance is added
to meet the overshoot requirement, undershoot at the
Dual and Combinable QPWM Graphics
Core Controllers for Notebook Computers
Figure 14. Current-Sense Configurations (Sheet 2 of 2)
30
______________________________________________________________________________________
SOAR
SW
R
is the switching frequency.
ESR
b) LOSSLESS INDUCTOR SENSING
from causing problems during load tran-
(
R
ESR
MAX17007
MAX17008
≤
⎡
⎢
⎢
⎣
(
+
V
Output Capacitor Selection
IN
R
PCB
−
PGND
CSH_
CSL_
V f
DH_
DL_
LX_
V
IN SW
OUT
)
≤
∆
L
)
V
I
LOAD MAX
OUT
N
N
V
H
L
STEP
(
⎤
⎥
⎥
⎦
V
RIPPLE
)
C
D
IN
L
INPUT (V
SAG
IN
R
)
1
L
INDUCTOR
rising load edge is no longer a problem (see the V
and V
tion). Thus, the output capacitor selection requires
carefully balancing capacitor chemistry limitations
(capacitance vs. ESR vs. voltage rating) and cost.
For Quick-PWM controllers, stability is determined by the
in-phase feedback ripple relative to the switching frequen-
cy, which is typically dominated by the output ESR. The
boundary of instability is given by the following equation:
where C
total ESR of the output capacitors, R
sense resistance, and A
determined by the ILIM setting. A
8 for ILIM settings of 5V, 3.3V, 2V, and GND, respectively.
For a 300kHz application, the effective zero frequency
must be well below 95kHz, preferably below 50kHz. For
the standard application circuit with ceramic output
capacitors, the output ripple cannot be relied upon to
be in phase with the inductor current due to the low
ESR of the ceramic capacitors. Stability is mainly
dependent on the current-sense gain. With ILIM = 2V,
A
approximately 3.5mΩ, then the ESR zero works out to:
This is well within the stability requirements.
CS
1/[2π x (2x330µF + 5 x 10µF) x 4 x 3.5mΩ] = 16kHz
R
= 4, and an effective current-sense resistance of
DCR
R
C
SOAR
2
EQ
OUT
Output Capacitor Stability Considerations
equations in the Transient Response sec-
is the total output capacitance, R
FOR THERMAL COMPENSATION:
R2 SHOULD CONSIST OF AN NTC RESISTOR IN
SERIES WITH A STANDARD THIN-FILM RESISTOR.
R
EFF
f
SW
R
π
C
EFF
OUT
=
≥
R
≥
CS
2
R
R
ESR
π
CS
DCR
2
R
f
=
is the current-sense gain as
SW OUT
EFF OUT
=
R1 + R2
+
C
1
R2
L
C
EQ
1
A
C
CS
CS CS
[
R1 R2
= R
1
equals 2, 2.67, 4, and
R
DCR
+
1
CS
]
is the current-
ESR
is the
SAG