HIP6304CB INTERSIL [Intersil Corporation], HIP6304CB Datasheet - Page 6

• Manufacturer Part Number: HIP6304CB
• Description: Microprocessor CORE Voltage Regulator Multi-Phase Buck PWM Controller
• Manufacturer: INTERSIL [Intersil Corporation]

Operation
Figure 1 shows a simplified diagram of the voltage regulation
and current control loops. Both voltage and current feedback
are used to precisely regulate voltage and tightly control
output currents, I
voltage loop comprises the Error Amplifier, Comparators,
gate drivers and output MOSFETs. The Error Amplifier is
essentially connected as a voltage follower that has as an
input, the Programmable Reference DAC and an output that
is the CORE voltage.
Voltage Loop
Feedback from the CORE voltage is applied via resistor R
to the inverting input of the Error Amplifier. This signal can
drive the Error Amplifier output either high or low, depending
upon the CORE voltage. Low CORE voltage makes the
amplifier output move towards a higher output voltage level.
Amplifier output voltage is applied to the positive inputs of
the Comparators via the Correction summing networks. Out-
of-phase sawtooth signals are applied to the two
Comparators inverting inputs. Increasing Error Amplifier
voltage results in increased Comparator output duty cycle.
This increased duty cycle signal is passed through the PWM
CIRCUIT with no phase reversal and on to the HIP6601,
again with no phase reversal for gate drive to the upper
MOSFETs, Q1 and Q3. Increased duty cycle or ON time for
the MOSFET transistors results in increased output voltage
to compensate for the low output voltage sensed.
Current Loop
The current control loop works in a similar fashion to the
voltage control loop, but with current control information applied
individually to each channel’s Comparator. The information
used for this control is the voltage that is developed across
r
conducting. A single resistor converts and scales the voltage
across the MOSFETs to a current that is applied to the Current
Sensing circuit within the HIP6304. Output from these sensing
circuits is applied to the current averaging circuit. Each PWM
channel receives the difference current signal from the
summing circuit that compares the average sensed current to
the individual channel current. When a power channel’s current
is greater than the average current, the signal applied via the
summing Correction circuit to the Comparator, reduces the
output pulse width of the Comparator to compensate for the
detected “above average” current in that channel.
Droop Compensation
In addition to control of each power channel’s output current,
the average channel current is also used to provide CORE
voltage “droop” compensation. Average full channel current
is defined as 50 A. By selecting an input resistor, R
amount of voltage droop required at full load current can be
programmed. The average current driven into the FB pin
results in a voltage increase across resistor R
direction to make the Error Amplifier “see” a higher voltage
DS(ON)
of each lower MOSFET, Q2 and Q4, when they are
L1
and I
L2
, of the two power channels. The
6
IN
that is in the
IN
, the
IN
HIP6304
at the inverting input, resulting in the Error Amplifier
adjusting the output voltage lower. The voltage developed
across R
Sensing and Balancing” section for more details.
Applications and Convertor Start-Up
Each PWM power channel’s current is regulated. This
enables the PWM channels to accurately share the load
current for enhanced reliability. The HIP6601, HIP6602 or
HIP6603 MOSFET driver interfaces with the HIP6304. For
more information, see the HIP6601, HIP6602 or HIP6603
data sheets.
The HIP6304 controls the two PWM power channels 180
degrees out of phase. Figure 2 shows the out of phase
relationship between the two PWM channels.
Power supply ripple frequency is determined by the channel
frequency, F
For example, if the channel frequency is set to 250kHz, the
ripple frequency is 500kHz.
The IC monitors and precisely regulates the CORE voltage
of a microprocessor. After initial start-up, the controller also
provides protection for the load and the power supply. The
following section discusses these features.
Initialization
The HIP6304 usually operates from an ATX power supply.
Many functions are initiated by the rising supply voltage to the
V
Start and other functions are initialized during this interval.
These circuits are controlled by POR, Power-On Reset. During
this interval, the PWM outputs are driven to a three state
condition that makes these outputs essentially open. This state
results in no gate drive to the output MOSFETs.
Once the V
level to insure proper internal function, the PWM outputs are
enabled and the Soft-Start sequence is initiated. If for any
reason, the V
POR circuit shuts the converter down and again three states
the PWM outputs.
Soft-Start
After the POR function is completed with V
4.375V, the Soft-Start sequence is initiated. Soft-Start, by its
slow rise in CORE voltage from zero, avoids an over-current
CC
pin of the HIP6304. Oscillator, Sawtooth Generator, Soft-
FIGURE 2. TWO PHASE PWM OUTPUT AT 500kHz
IN
CC
is equal to the “droop” voltage. See the “Current
SW
CC
voltage reaches 4.375V (+125mV), a voltage
, multiplied by the number of active channels.
voltage drops below 3.875V (+125mV). The
CC
reaching
PWM 1
PWM 2