HIP6311CB Intersil, HIP6311CB Datasheet - Page 12

• Manufacturer Part Number: HIP6311CB
• Description: IC CTRLR PWM MULTIPHASE 20-SOIC
• Manufacturer: Intersil

Specifications of HIP6311CB

• Pwm Type: Controller
• Number Of Outputs: 4
• Frequency - Max: 305kHz
• Voltage - Supply: 4.75 V ~ 5.25 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 20-SOIC (7.5mm Width)
• Frequency-max: 305kHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Duty Cycle: -

current creates a voltage drop across R
increases the apparent V
current, causing the system to decrease V
balance at the FB pin. This is the desired “droop” voltage
used to maintain V
conditions.
With a high dv/dt load transient, typical of high performance
microprocessors, the largest deviations in output voltage
occur at the leading and trailing edges of the load transient.
In order to fully utilize the output-voltage tolerance range, the
output voltage is positioned in the upper half of the range
when the output is unloaded and in the lower half of the
range when the controller is under full load. This droop
compensation allows larger transient voltage deviations and
thus reduces the size and cost of the output filter
components.
R
the normal full load current 50µA applied through the R
resistor (or at a different full load current if adjusted as under
“Over-Current, Selecting R
R
For a Vdroop of 80mV, R
The AC feedback components, R
relation to R
Current Balancing
The detected currents are also used to balance the phase
currents.
Each phase’s current is compared to the average of all
phase currents, and the difference is used to create an offset
in that phase’s PWM comparator. The offset is in a direction
to reduce the imbalance.
The balancing circuit can not make up for a difference in
r
higher r
reduced.
Figures 8 and 9 show the inductor current of a two phase
system without and with current balancing.
Inductor Current
The inductor current in each phase of a multi-phase Buck
converter has two components. There is a current equal to
the load current divided by the number of phases (I
and a sawtooth current, (i
sawtooth component is dependent on the size of the
inductors, the switching frequency of each phase, and the
values of the input and output voltage. Ignoring secondary
effects, such as series resistance, the peak to peak value of
the sawtooth current can be described by:
DS(ON)
IN
IN
should be selected to give the desired “droop” voltage at
= Vdroop/50µA
DS(ON)
between synchronous rectifiers. If a FET has a
IN
.
, the current through that phase will be
CORE
IN
CORE
within limits under transient
PK-PK
ISEN
= 1.6kΩ
12
voltage with increasing load
” above).
) due to switching. The
FB
and Cc, are scaled in
IN
. This drop
CORE
to maintain
LT
/ n),
ISEN
HIP6311
HIP6311
i
Where: V
Example: For V
Then i
The inductor, or load current, flows alternately from V
through Q1 and from ground through Q2. The HIP6311
samples the on-state voltage drop across each Q2 transistor
to indicate the inductor current in that phase. The voltage
drop is sampled 1/3 of a switching period, 1/F
turned OFF and Q2 is turned on. Because of the sawtooth
current component, the sampled current is different from the
PK-PK
FIGURE 8. TWO CHANNEL MULTIPHASE SYSTEM WITH
FIGURE 9. TWO CHANNEL MULTIPHASE SYSTEM WITH
25
20
15
10
5
0
PK-PK
= (V
25
20
15
10
5
0
CORE
IN
F
= 4.3A
V
SW
CURRENT BALANCING DISABLED
CURRENT BALANCING ENABLED
x V
IN
L = value of the inductor
CORE
F
= DC value of the output or V
= DC value of the input or supply voltage
= switching frequency
CORE
V
SW
IN
L = 1.3µH,
= 1.6V,
= 12V,
= 250kHz,
- V
CORE
2
) / (L x F
SW
SW
ID
December 27, 2004
x V
, after Q1 is
voltage
IN
)
IN
FN4817.3