MAX17082GTL+ Maxim Integrated Products, MAX17082GTL+ Datasheet - Page 42

• Manufacturer Part Number: MAX17082GTL+
• Description: IC CTLR PWM DUAL IMVP-6.5 40TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17082GTL+

• Applications: Controller, Intel IMVP-6.5™
• Voltage - Input: 4.5 ~ 5.5 V
• Number Of Outputs: 1
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: Details

Dual-Phase, Quick-PWM Controllers for
IMVP-6+/IMVP-6.5 CPU Core Power Supplies
The switching frequency and operating point (% ripple
current or LIR) determine the inductor value as follows:
where η
Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite
cores are often the best choice, although powdered
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 inductor ripple current impacts transient-response
performance, especially at low V
Low inductor values allow the inductor current to slew
faster, replenishing charge removed from the output fil-
ter capacitors by a sudden load step. The amount of
output sag is also a function of the maximum duty fac-
tor, which can be calculated from the on-time and mini-
mum off-time. For a dual-phase controller, the
worst-case output sag voltage can be determined by:
where t
Electrical Characteristics table). The amount of overshoot
due to stored inductor energy can be calculated as:
where η
42
V
SAG
______________________________________________________________________________________
=
TOTAL
L
TOTAL
2
OFF(MIN)
ΔI
V
C
=
L
SOAR
OUT OUT
LOAD(MAX)
(
η
Δ
2
I
PEAK
TOTAL
C
I
LOAD(MAX)
is the total number of active phases.
V
OUT
is the total number of phases.
≈
PEAK
=
2η
is the minimum off-time (see the
⎛
⎜
⎝
⎡
⎢
⎢
⎣
(
⎛
⎜
⎝
⎛
⎜
⎝
Δ
f
TOTAL OUT OUT
SW LOAD MAX
I
⎡
⎢
⎢
⎣
LOAD MAX
(
I
LOAD MAX
⎛
⎝ ⎜
):
V
η
)
IN
V
I
2
V
TOTAL
OUT
IN
-
⎡
⎢
⎣
V
(
2
⎛
⎝ ⎜
C
IN
(
-
V
V
V
T
V
OUT
OUT SW
IN
S S W
(
Transient Response
OUT
V
Inductor Selection
)
IN
)
⎞
⎠ ⎟
⎞
⎟
⎠
V
IN
)
)
T
2
⎛
⎝ ⎜
+
)
T
LIR
1
SW
L
t
- V
OFF MIN
+
⎞
⎠ ⎟
⎞
⎟
⎠
LIR
⎞
⎟
⎠
OUT
+
2
⎛
⎝ ⎜
- - 2
(
t
V
OFF
⎞
⎠ ⎟
t
V
OUT
OFF MIN
I I N
)
differentials.
⎤
⎥
⎥
⎦
(M M IN
(
⎞
⎠ ⎟
)
⎤
⎥
⎦
)
⎤
⎥
⎥
⎦
+
The minimum current-limit threshold must be high
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The val-
ley of the inductor current occurs at I
half the ripple current; therefore:
where η
I
voltage divided by the current-sense resistor (R
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 CPU V
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 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 by
reducing the total inductor ripple current. For multi-
phase operation, the maximum ESR to meet ripple
requirements is:
where η
f
capacitance value required relates to the physical size
needed to achieve low ESR, as well as to the chemistry
of the capacitor technology. Thus, the capacitor is usu-
ally selected by ESR and voltage rating rather than by
capacitance value (this is true of polymer types).
LIMIT(LOW)
SW
is the switching frequency per phase. The actual
R
ESR
TOTAL
TOTAL
CORE
I
LIMIT LOW
(
equals the minimum current-limit threshold
R
≤
ESR
⎡
⎢
⎢
⎣
is the total number of active phases, and
is the total number of active phases and
converters and other applications where
(
(
V
IN
+
R
- η
)
Output Capacitor Selection
PCB
>
TOTAL OUT
Setting the Current Limit
⎛
⎜
⎝
V f
I
)
IN SW
LOAD MAX
≤
η
TOTAL
Δ
V
I
LOAD MAX
L
(
V
STEP
)
V
)
(
OUT
⎞
⎟
⎠
⎛
⎝ ⎜
LOAD(MAX)
1
-
)
⎤
⎥
⎥
⎦
LIR
V
2
RI
⎞ ⎞
⎠ ⎟
P P PLE
SENSE
minus
).