MAX17480GTL+ Maxim Integrated Products, MAX17480GTL+ Datasheet - Page 39

• 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

By design, the AMD mobile serial VID application
should regard each of the MAX17480 SMPSs as inde-
pendent, single-phase SMPSs. The switching frequen-
cy and operating point (% ripple current or LIR)
determine the inductor value as follows:
where I
and f
Find a low-loss inductor with the lowest possible DC
resistance that fits in the allotted dimensions. If using a
swinging inductor (where the inductance decreases lin-
early with increasing current), evaluate the LIR with
properly scaled inductance values. For the selected
inductance value, the actual peak-to-peak inductor
ripple current (∆I
Ferrite cores are often the best choice, although pow-
dered iron is inexpensive and can work well at 200kHz.
The core must be large enough not to saturate at the
peak inductor current (I
The MAX17480 overcurrent protection employs a peak
current-sensing algorithm that uses either current-
sense resistors or the inductor’s DCR as the current-
sense element (see the Current Sense section). Since
the controller limits the peak inductor current, the maxi-
mum average load current is less than the peak cur-
rent-limit threshold by an amount equal to half the
inductor ripple current. Therefore, the maximum load
capability is a function of the current-sense resistance,
inductor value, switching frequency, and input-to-out-
put voltage difference. When combined with the output
undervoltage-protection circuit, the system is effectively
protected against excessive overload conditions.
The peak current-limit threshold is set by the voltage
difference between ILIM and REF using an external
resistor-divider:
V
CS(PK)
SW
LOAD(MAX)
is the switching frequency per phase.
I
PEAK
= V
Core Peak Inductor Current Limit (ILIM12)
∆I
L
I
=
INDUCTOR
CSP
LIMIT(PK)
=
⎛
⎜
⎜
⎝
f
INDUCTOR
SW LOAD MAX
⎛
⎜
⎝
_ - V
Core SMPS Design Procedure
I
______________________________________________________________________________________
LOAD MAX
is the maximum current per phase,
I
V
IN
η
CSN
PH
PEAK
= V
−
(
=
V
(
_ = 0.052 x (V
V
OUT
) is defined by:
CS(PK)
OUT
):
)
⎞
⎟ +
⎠
Core Inductor Selection
)
LIR
V f
(
⎛
⎜
⎝
IN SW
V
∆
IN
/R
⎞
⎟
⎟
⎠
I
INDUCTOR
⎛
⎜ ⎜
⎝
SENSE
−
V
L
V
OUT
V
2
IN
OUT
REF
⎞
⎟
⎠
)
AMD 2-/3-Output Mobile Serial
- V
⎞
⎟
⎠
ILIM12
)
where R
sense element (inductors’ DCR or current-sense resis-
tor), and I
phase). The peak current-limit threshold voltage adjust-
ment range is from 10mV to 50mV.
The output filter capacitor must have low enough ESR to
meet output ripple and load-transient requirements. In
CPU V
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 non-CPU 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 capaci-
tor’s ESR. When operating multiphase systems out-of-
phase, the peak inductor currents of each phase are
staggered, resulting in lower output ripple voltage
(V
For nonoverlapping, multiphase operation (V
the maximum ESR to meet the output-ripple-voltage
requirement is:
where f
actual capacitance value required relates to the physi-
cal size needed to achieve low ESR, as well as to the
chemistry of the capacitor technology. Thus, the capac-
itor selection is usually limited by ESR and voltage rat-
ing rather than by capacitance value (this is true of
polymer types).
The capacitance value required is determined primarily
by the output transient-response requirements. Low
inductor values allow the inductor current to slew faster,
replenishing charge removed from or added to the out-
put filter capacitors by a sudden load step. Therefore,
the amount of output soar when the load is removed is
a function of the output voltage and inductor value. The
minimum output capacitance required to prevent over-
shoot (V
calculated as:
RIPPLE
CORE
SW
SENSE
) by reducing the total inductor ripple current.
SOAR
LIMIT(PK)
is the switching frequency per phase. The
R
converters and other applications where the
(
ESR
C
R
) due to stored inductor energy can be
ESR
OUT
is the resistance value of the current-
≤
is the desired peak current limit (per
+
⎡
⎢
⎢
⎣
≥
(
R
Core Output Capacitor Selection
V
VID Controller
(
PCB
IN
∆
2
I
−
LOAD MAX
V
V f
)
V
IN SW
OUT SOAR
≤
OUT
∆
(
V
I
LOAD MAX
L
)
V
V
OUT
STEP
)
)
2
(
L
⎤
⎥
⎥
⎦
V
RIPPLE
)
IN
≥ V
OUT
39
),