MAX17082GTL+ Maxim Integrated Products, MAX17082GTL+ Datasheet - Page 37

• 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

When DPRSLPVR is pulled high, the MAX17021/
MAX17082/MAX17482 operate with a single-phase
pulse-skipping mode. The pulse-skipping mode
enables the driver’s zero-crossing comparator, so the
controller pulls DL1 low when it detects zero inductor
current. This keeps the inductor from discharging the
output capacitors and forces the controller to skip puls-
es under light-load conditions to avoid overcharging
the output.
During downward transitions in pulse-skipping operation,
the controller temporarily sets the OVP threshold to
default, preventing false OVP faults when the transition to
pulse-skipping operation coincides with a VID code
change. Once the error amplifier detects that the output
voltage is in regulation, the OVP threshold tracks the
selected VID DAC code. The MAX17021/MAX17082/
MAX17482 automatically use forced-PWM operation dur-
ing soft-shutdown, regardless of the DPRSLPVR and PSI
configuration.
In skip mode (DPRSLPVR = high), an inherent automatic
switchover to PFM takes place at light loads (Figure 9).
This switchover is affected by a comparator that trun-
cates the low-side switch on-time at the inductor cur-
rent’s zero crossing. The zero-crossing comparator
senses the inductor current across the low-side
MOSFETs. Once V
comparator threshold (see the Electrical Characteristics
table), the comparator forces DL_ low. This mechanism
causes the threshold between pulse-skipping PFM and
nonskipping PWM operation to coincide with the
boundary between continuous and discontinuous
inductor-current operation. The PFM/PWM crossover
occurs when the load current of each phase is equal to
1/2 the peak-to-peak ripple current, which is a function
of the inductor value (Figure 9). For a battery input
range of 7V to 20V, this threshold is relatively constant,
with only a minor dependence on the input voltage due
to the typically low duty cycles. The total load current at
the PFM/PWM crossover threshold (I
approximately:
where η
I
LOAD SKIP
TOTAL
Light-Load Pulse-Skipping Operation
(
IMVP-6+/IMVP-6.5 CPU Core Power Supplies
)
is the number of active phases.
=
Automatic Pulse-Skipping Switchover
η
______________________________________________________________________________________
TOTAL
LX
Dual-Phase, Quick-PWM Controllers for
drops below the zero-crossing
⎛
⎝ ⎜
T
SW OUT
V
L
⎞
⎠ ⎟
(Deeper Sleep)
⎛ ⎛
⎝ ⎜
V
IN
LOAD(SKIP)
-
V
IN
V
OUT
⎞
⎠ ⎟
) is
The switching waveforms might appear noisy and asyn-
chronous when light loading activates pulse-skipping
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs between
PFM noise and light-load efficiency are made by vary-
ing the inductor value. Generally, low inductor values
produce a broader efficiency vs. load curve, while higher
values result in higher full-load efficiency (assuming that
the coil resistance remains fixed) and less output-voltage
ripple. Penalties for using higher inductor values include
larger physical size and degraded load-transient
response, especially at low input-voltage levels.
Figure 9. Pulse-Skipping/Discontinuous Crossover Point
0
Δi
Δt
ON-TIME
V
BATT
– V
L
OUT
TIME
I
LOAD
I
PEAK
= I
PEAK
/2
37