Datasheet

MAX17021/MAX17082/MAX17482
Differential Remote Sense
The MAX17021/MAX17082/MAX17482 include differen-
tial, remote-sense inputs to eliminate the effects of volt-
age drops along the PCB traces and through the
processor’s power pins. The feedback-sense node con-
nects to the voltage-positioning resistor (R
FB
). The
ground-sense (GNDS) input connects to an amplifier
that adds an offset directly to the target voltage, effec-
tively adjusting the output voltage to counteract the volt-
age drop in the ground path. Connect the
voltage-positioning resistor (R
FB
), and ground-sense
(GNDS) input directly to the processor’s remote-sense
outputs, as shown in Figure 1.
Integrator Amplifier
An integrator amplifier forces the DC average of the FB
voltage to equal the target voltage. This transconduc-
tance amplifier integrates the feedback voltage and pro-
vides a fine adjustment to the regulation voltage (Figure
3), allowing accurate DC output-voltage regulation
regardless of the output ripple voltage. The integrator
amplifier has the ability to shift the output voltage by
±100mV (typ). The differential input-voltage range is at
least ±60mV total, including DC offset and AC ripple.
The MAX17021/MAX17082/MAX17482 disable the inte-
grator by connecting the amplifier inputs together at the
beginning of all VID transitions done in pulse-skipping
mode (DPRSLPVR = high). The integrator remains dis-
abled until 20μs after the transition is completed (the
internal target settles) and the output is in regulation
(edge detected on the error comparator).
Transient-Overlap Operation
When a transient occurs, the response time of the con-
troller depends on how quickly it can slew the inductor
current. Multiphase controllers that remain 180° out-of-
phase when a transient occurs actually respond slower
than an equivalent single-phase controller. To provide
fast-transient response, the MAX17021/MAX17082/
MAX17482 support a phase-overlap mode, which
allows the dual regulators to operate in-phase when
heavy load transients are detected, effectively reducing
the response time. After either high-side MOSFET turns
off, if the output voltage does not exceed the regulation
voltage when the minimum off-time expires, the con-
troller simultaneously turns on both high-side MOSFETs
during the next on-time cycle. This maximizes the total
inductor current slew rate. The phases remain over-
lapped until the output voltage exceeds the regulation
voltage after the minimum off-time expires.
After the phase-overlap mode ends, the controller automat-
ically begins with the opposite phase. For example, if the
secondary phase provided the last on-time pulse before
overlap operation began, the controller starts switching
with the main phase when overlap operation ends. Table 3
is the operating mode truth table.
Nominal Output-Voltage Selection
The nominal no-load output voltage (V
TARGET
) is
defined by the selected voltage reference (VID DAC)
plus the remote ground-sense adjustment (V
GNDS
) as
defined in the following equation:
V
TARGET
= V
FB
= V
DAC
+ V
GNDS
where V
DAC
is the selected VID voltage. On startup, the
MAX17021/MAX17082/MAX17482 slew the target volt-
age from ground to the preset boot voltage.
DAC Inputs (D0–D6)
The digital-to-analog converter (DAC) programs the
output voltage using the D0–D6 inputs. D0–D6 are low-
voltage (1.0V) logic inputs, designed to interface direct-
ly with the CPU. Do not leave D0–D6 unconnected.
Changing D0–D6 initiates a transition to a new output-
voltage level. Change D0–D6 together, avoiding greater
than 20ns skew between bits. Otherwise, incorrect DAC
readings might cause a partial transition to the wrong
voltage level followed by the intended transition to the
correct voltage level, lengthening the overall transition
time. The available DAC codes and resulting output
voltages are compatible with the IMVP-6/IMVP-6+ and
IMVP-6.5 (Table 4) specifications.
Dual-Phase, Quick-PWM Controllers for
IMVP-6+/IMVP-6.5 CPU Core Power Supplies
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