ADP3203JRU-10-RL7 AD [Analog Devices], ADP3203JRU-10-RL7 Datasheet - Page 9

• Manufacturer Part Number: ADP3203JRU-10-RL7
• Description: 2-Phase IMVP-II & IMVP-III Core Controller for Mobile CPUs
• Manufacturer: AD [Analog Devices]

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THEORY OF OPERATION
Overview
Featuring a new proprietary single-or-dual-channel buck
converter hysteretic control architecture developed by Analog
Devices, Inc., the ADP3203 is the optimal core voltage control
solution for both IMVP-II & -III generation microprocessors.
The complex multi-tiered regulation requirements of either
IMVP specification are easily implemented with the highly
integrated functionality of this controller.
Power Conversion Control Architecture
Driving of the individual channels is accomplished using
external drivers, such as the ADP3415. One PWM interface pin
per channel, OUT1 and OUT2, is provided. A separate pin,
DRVLSD, commands the driver to enable or disable synchro-
nous operation during the off time of each channel. The same
DRVLSD pin is connected to both drivers.
The ADP3203 utilizes hysteretic control. The resistor from the
HYSSET pin to ground sets up a current that is switched bi-
directionally into a resistor interconnected between RAMP and
CS+ pins. The switching of this current sets the hysteresis.
In its dual-channel configuration, the hysteretic control requires
multiplexing information in the two channels. The inductor
current of the channel that is driven high is controlled against
the upper hysteresis limit. During the common off-time of the
two channels, the inductor currents are averaged together and
compared against the lower hysteresis limit. This proprietary
off-time averaging technique serves to eliminate a systematic
offset that otherwise appears in a fully multiplexed hysteretic
control system.
Compensation
As with all ADI products for core voltage control, the controller
is compatible with ADOPT™ compensation, which provides
the optimum output voltage containment within a specified
voltage window or along a specified load-line using the fewest
possible number of output capacitors. The inductor ripple
current is kept at a fixed programmable value while the output
voltage is regulated with fully programmable voltage positioning
parameters, which can be tuned to optimize the design for any
particular CPU regulation specifications. By controlling the
ripple current rather than ripple voltage, the frequency varia-
tions associated with changes in output impedance for standard
ripple regulators will not appear.
Feedback/Current Sensing
Accurate current sensing is needed to accomplish output
voltage positioning accurately, which, in turn, is required to
allow the minimum number of output capacitors to be used to
contain transients. A current sense resistor is used between
each inductor and the output capacitors. To allow the control
to operate without amplifiers, the negative feedback signal is
multiplexed from the inductor, or upstream, side of the current
sense resistors, and a positive feedback signal, if needed for
load-line tuning is taken from the output, or downstream, side.
Output Voltage Programming by VID, Offsets, & Load-Line
In the IMVP-II & -III specifications, the output voltage is a
function of both the core current – according to a specified load
line – and the system operating mode – i.e., performance or
battery optimized, normal or deepsleep clocking state, or
deepersleep. The VID code programs the “nominal” core
voltage. The core voltage decreases as a function of load current
PRELIMINARY TECHNICAL DATA
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along the load line (which is synonymous with an output
resistance of the power converter). The core voltage is also
offset by a DC value – usually specified as a percentage –
depending on the operating mode. The voltage offset is also
called a “shift”.
Two pins, BSHIFT and DSHIFT, are used to program the
magnitude of the voltage shifts. The voltage shifts are accom-
plished by injecting current at the node of the negative input
pin of the feedback comparator. Resistive termination at the
pins determines the magnitude of the voltage shifts.
Two other pins, BOM and DSLP, are used to activate the
respective two shifts only in their active low states. In the
ADP3203, the shifts are mutually exclusive, with the
DeepSleep shift (controlled by DSLP and DSHIFT pins) being
the dominant one. Another pin, DPRSLP, eliminates both
shifts only in its active high state. Its assertion corresponds to
the DeeperSleep operating mode.
Current Limiting
The current programmed at the HYSSET pin and a resistor
from the CS- pin to the common node of the current sense
resistors sets the current limit. If the current limit threshold is
triggered, a hysteresis is applied to the threshold so that
hysteretic control is maintained during a current limited
operating mode.
Softstart and Hiccup
A capacitor from the SS pin to determines both the soft-start
time and the frequency at which hiccup will occur under a
continuous short circuit or overload.
System Signal Interface
Several pins of the ADP3203 are meant to connect directly to
system signals. The VID pins connect to the system VID
control signals. The DPRSLP pin connects to the system’s
DPRSLPVR signal. The DSLP pin connects to the system’s
DPSLP or STPCPU signal. The BOM signal connects to the
system’s GMUXSEL signal. In an IMVP-II system, the
GMUXSEL signal preceeds any VID code change with a few
nanoseconds, while in an IMVP-III system, it follows it with a
maximum 12 µs delay. To comply with both specifications, the
ADP3203 has a VID register in front of the DAC inputs that is
written by a short pulse generated at the rising or falling edge of
the GMUSEL signal. In an IMVP-II configuration, if the
external VID multiplex settling time is longer than the internal
VID register's write pulse-width, then the insertion of an
external RC delay network in the GMUXSEL signal path (in
front of the BOM pin) is recommended. The Intel spec calls for
maximum 200 ns VID code set-up time. This specification can
be met with a simple RC network which consists of only a
220 k resistor, and no external capacitor just the BOM pin's
capacitance.
Undervoltage Lockout
The ADP3203’s supply pin, V
(UVLO) functionality to ensure that if V
maintain proper operation, the IC will remain off and in a low
current state.
CC,
has undervoltage lockout
CC
is too low to
ADP3203