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

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

ADP3203
Over-Voltage Protection (OVP) & Reverse-Voltage
Protection (RVP)
The ADP3203 features a comprehensive redundantly moni-
tored OVP and RVP implementation to protect the CPU core
against an excessive or reverse voltage, e.g., as might be
induced by a component or connection failure in the control or
power stage. Two pins are associated with the OVP/RVP
circuitry – a pin for output voltage feedback, COREFB, which
is used also for power good monitoring but not for voltage
regulation, and an output pin, CLAMP.
The CLAMP pin defaults to a low state at startup of the
ADP3203 and remains low until an OV or RV condition is
detected. If either condition is detected, the CLAMP pin is
switched and latched to the VCC pin. The high state of the
CLAMP pin is reset only after several milliseconds as the
softstart pin discharges.
For maximum and fastest protection, the CLAMP pin
should be used to drive the gate of a power MOSFET
whose drain-source is connected across the CPU core
voltage. Detection of OV or RV will clamp the core voltage
to essentially zero, thus quickly removing the fault condition
and preventing further energy from being applied to the
CPU core.
For a less comprehensively protective but also less costly
solution, the CLAMP pin may be used to latch the discon-
nection of input power. The latch should be powered
whenever any input power source is present. Typically,
such a latching circuit is already present in a system design,
so it becomes only a matter of allowing the CLAMP pin to
also trigger the latch. In this configuration, the latched off
state of the system would be indicative of a system failure.
The OV/RV protective means is via not allowing the
continued application of energy to the CPU core. The
design objective should be to ensure that the CPU core
could safely absorb the remaining energy in the power
converter, however, since this energy is not clamped as in
the preferred configuration.
LAYOUT CONSIDERATIONS
Advantages in PCB Layout
Analog Devices Inc., provides ADP3203/3415 as a dedicated
2-phase power management solution for IMVP-3 Intel P4
mobile core supply.
This 2-phase solution separates the controller (ADP3203)
and MOSFET driver (ADP3415). Today, most
motherboards only leave small pieces of PCB area for power
management circuit. Therefore, the separation of the
controller and the MOSFET drivers gives much greater
freedom in layout than any single chip solution can do.
Meanwhile, the separation also provides the freedom to
place the analog controller in a relatively quiet area in the
motherboard. This can minimize the susceptibility of the
controller to injected noise. Any single chip solution with a
high speed loop design will suffer larger susceptibility to
jitter that appears as modulation of the output voltage.
PRELIMINARY TECHNICAL DATA
–10–
The ADP3203 maximizes the integration of IMVP-3
features. Therefore, no additional externally implemented
functions are required to comply with IMVP-3 specifica-
tions. This saves PCB area for component placement on the
motherboard.
PCB Layout Consideration for ADP3203/3415
The following guidelines are recommended for optimal
performance of the ADP3203 and ADP3415 in a power
converter. The circuitry is considered in three parts: the power
switching circuitry, the output filter, and the control circuitry.
Placement Overview
1. For ideal component placement, the output filter
2. Whenever a power-dissipating component (e.g., a power
Power Switching Circuitry
ADP3415, MOSFETs, and Input Capacitors
3. Locate the ADP3415 near the MOSFETs so the loop
4. Locate the input bypass MLC capacitors close to the
5. Make provisions for thermal management of all the
capacitors will divide the power switching circuitry from
the control section. As an approximate guideline,
considered on a single-sided PCB, the best layout would
have components aligned in the following order:
ADP3415, MOSFETs and input capacitor, output
inductor, current sense resistor, output capacitors,
control components and ADP3203. Note that the
ADP3203 and ADP3415 are completely separated for
an ideal layout, which is impossible with a single-chip
solution. This keeps the noisy switched power section
isolated from the precision control section and gives
more freedom in the layout of the power switching
circuitry.
MOSFET) is soldered to a PCB, the liberal use of vias,
both directly on the mounting pad if possible and
immediately surrounding it, is recommended. Two
important reasons for this are: improvement of the
current rating through the vias (if it is a current path),
and improved thermal performance- especially if there is
opportunity to spread the heat with a plane on the
opposite side of the PCB.
inductance in the path of the top gate drive returned to the
SW pin is small, and similarly for the bottom gate drive
whose return path is the ground plane. The GND pin
should have at least one very close via into the ground
plane.
MOSFETs so that the physical area of the loop enclosed
in the electrical path through the bypass capacitor and
around through the top and bottom MOSFETs (drain-
source) is small and wide. This is the switching power
path loop.
MOSFETs. Heavy copper and wide traces to ground
and power planes will help to pull the heat out.
Heatsinking by a metal tap soldered in the power plane
REV. PrD