MAX17480GTL+ Maxim Integrated Products, MAX17480GTL+ Datasheet - Page 38

• Manufacturer Part Number: MAX17480GTL+
• Description: IC CTRLR SERIAL VID 40-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17480GTL+

• Applications: Processor
• Current - Supply: 5mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Output Voltage Range: - 10 V to + 10 V
• Input Voltage Range: 4 V to 26 V
• Input Current: 5 mA
• Power Dissipation: 1778 mW
• Operating Temperature Range: - 40 C to + 105 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AMD 2-/3-Output Mobile Serial
VID Controller
The offset and current-limit settings of the NB SMPS
can be set by the ILIM3 pin setting. Table 6 shows the
ILIM3 pin voltage levels and the corresponding settings
for the offset and current limit of the NB SMPS. The NB
offset is always present regardless of PSI_L setting.
The I
mode is precisely 25% of the corresponding positive
current-limit threshold.
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
• Maximum Load Current: There are two values to
38
Table 6. ILIM3 Setting
must accommodate the worst-case high AC adapter
voltage. The minimum value (V
the lowest input voltage after drops due to connectors,
fuses, and battery selector switches. If there is a choice
at all, lower input voltages result in better efficiency.
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
drives the selection of input capacitors, MOSFETs,
and other critical heat-contributing components.
Modern notebook CPUs generally exhibit I
I
For multiphase systems, each phase supports a frac-
tion of the load, depending on the current balancing.
When properly balanced, the load current is evenly
distributed among each phase:
where η
LOAD(MAX)
______________________________________________________________________________________
LX3MIN
ILIM3
GND
LOAD
V
CC
PH
is the total number of active phases.
) determines the thermal stresses and thus
minimum current-limit threshold in skip
x 80%.
Offset and Current-Limit Setting
SMPS Design Procedure
I
LOAD PHASE
PEAK CURRENT
(
LIMIT (A)
5.25
4.25
)
for NB SMPS (ILIM3)
=
IN(MIN)
I
LOAD
η
PH
LOAD(MAX)
) must account for
SKIP CURRENT
LIMIT (A)
1.05
1.3
IN(MAX)
LOAD
) deter-
=
)
• Core Switching Frequency: This choice determines
• Inductor Operating Point: This choice provides
CURRENT (A)
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
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 minimum
on-time at the highest input voltage and lowest output
voltage must be greater than the 150ns (max) mini-
mum 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 (PSI_L = 0), 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 170ns
(max) minimum on-time specification in the Electrical
Characteristics table:
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 out-
put noise due to increased ripple current. The mini-
mum practical inductor value is one that causes the
circuit to operate at the edge of critical conduction
(where the inductor current just touches zero with
every cycle at maximum load). Inductor values lower
than this grant no further size-reduction benefit. The
optimum operating point is usually found between
20% and 50% ripple current.
MAX DC
4.75
3.75
t
ON MIN
V
OUT(MIN)
(
)
≤
R
SENSE
/V
DROOP (mV)
IN(MAX)
FULL-LOAD
-26.13
-20.63
(
V
IN MAX
(
LV
x t
IDLE
SW
)
−
> t
V
OUT MIN
IN
ON(MIN)
2
. The optimum
(
OFFSET
(mV)
12.5
12.5
)
)