MAX17009GTL+ Maxim Integrated Products, MAX17009GTL+ Datasheet - Page 35

• Manufacturer Part Number: MAX17009GTL+
• Description: IC CTLR VIDEO SERIAL DUAL 40TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17009GTL+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 6. OPTION Pin Settings
The +12.5mV offset and the transient-phase repeat fea-
tures of the MAX17009 can be selectively enabled and
disabled by the OPTION pin setting. Table 6 shows the
OPTION pin voltage levels and the features that are
enabled. See the Transient Phase Repeat section for a
detailed description of the respective features. When
the offset is enabled, setting the PSI_L bit low disables
the offset reducing power consumption in the low-
power state.
Firmly establish the input voltage range and maximum
load current before choosing a switching frequency
and inductor operating point (ripple-current ratio). The
primary design trade-off lies in choosing a good switch-
ing frequency and inductor operating point, and the fol-
lowing four factors dictate the rest of the design:
• Input voltage range: The maximum value (V
•
OPTION
OPEN
must accommodate the worst-case high AC
adapter voltage. The minimum value (V
must account for the lowest input voltage after
drops due to connectors, fuses, and battery selec-
tor switches. If there is a choice at all, lower input
voltages result in better efficiency.
Maximum load current: There are two values to
consider. The peak load current (I
mines the instantaneous component stresses and fil-
tering requirements, and thus drives output capacitor
selection, inductor saturation rating, and the design
of the current-limit circuit. The continuous load cur-
rent (I
thus drives the selection of input capacitors,
MOSFETs, and other critical heat-contributing com-
ponents. Modern notebook CPUs generally exhibit
I
For multiphase systems, each phase supports a
fraction of the load, depending on the current bal-
ancing. When properly balanced, the load current
is evenly distributed among each phase:
GND
V
LOAD
REF
CC
LOAD
= I
LOAD(MAX)
OFFSET ENABLED
) determines the thermal stresses and
SMPS Design Procedure
______________________________________________________________________________________
Offset and Transient-Phase
0
0
1
1
x 80%.
AMD Mobile Serial VID Dual-Phase
Repeat (OPTION)
TRANSIENT-PHASE
REPEAT ENABLED
LOAD(MAX)
0
1
0
1
IN(MIN)
IN(MAX)
) deter-
Fixed-Frequency Controller
)
)
•
•
By design, the AMD Mobile Serial VID application
should regard each of the MAX17009 SMPSs as inde-
pendent, single-phase regulators. The switching fre-
quency and operating point (% ripple current or LIR)
determine the inductor value as follows:
where η
Switching frequency: This choice determines the
basic trade-off between size and efficiency. The
optimal frequency is largely a function of maximum
input voltage, due to MOSFET switching losses that
are proportional to frequency and V
mum frequency is also a moving target, due to
rapid improvements in MOSFET technology that are
making higher frequencies more practical.
When selecting a switching frequency, the mini-
mum on-time at the highest input voltage and low-
est output voltage must be greater than the 185ns
(max) minimum on-time specification in the
Electrical Characteristics table:
A good rule is to choose a minimum on-time of at
least 200ns.
When in pulse-skipping operation SKIP_ = GND,
the minimum on-time must take into consideration
the time needed for proper skip-mode operation.
The on-time for a skip pulse must be greater than
the 185ns (max) minimum on-time specification in
the Electrical Characteristics table:
Inductor operating point: This choice provides
trade-offs between size vs. efficiency and transient
response vs. output noise. Low inductor values pro-
vide better transient response and smaller physical
size, but also result in lower efficiency and higher
output noise due to increased ripple current. The
minimum practical inductor value is one that causes
the circuit to operate at the edge of critical conduc-
tion (where the inductor current just touches zero
with every cycle at maximum load). Inductor values
lower than this grant no further size-reduction bene-
fit. The optimum operating point is usually found
between 20% and 50% ripple current.
t
ONMIN
V
OUT(MIN)
PH
is the total number of active phases.
≤
I
LOAD PHASE
R
SENSE IN MAX
/ V
(
IN(MAX)
(
V
LV
(
)
=
x T
IDLE
Inductor Selection
I
LOAD
η
SW
)
PH
−
V
> t
OUT MIN
ONMIN
IN
(
2
. The opti-
)
)
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