HIP6304 Intersil Corporation, HIP6304 Datasheet - Page 10

• Manufacturer Part Number: HIP6304
• Description: Microprocessor CORE Voltage Regulator Multi-Phase Buck PWM Controller
• Manufacturer: Intersil Corporation

R
the normal full load current 50 A 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 the two
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
r
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
The 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:
i
Where: V
Example: For V
Then i
PK-PK
DS(ON)
DS(ON)
IN
IN
should be selected to give the desired “droop” voltage at
= Vdroop / 50 A
PK-PK
= (V
, the current through that phase will be reduced.
between synchronous rectifiers. If a FET has a higher
CORE
IN
F
IN
V
= 4.3A
SW
x V
.
IN
L = value of the inductor
CORE
F
CORE
= DC value of the output or V
= DC value of the input or supply voltage
= switching frequency
V
SW
IN
L = 1.3 H,
= 1.6V,
= 12V,
= 250kHz,
- V
IN
PK-PK
ISEN
CORE
= 1.6k
10
” above).
) resulting from switching.
2
FB
) / (L x F
and Cc, are scaled in
SW
x V
ID
voltage
IN
LT
)
/ n),
ISEN
HIP6304
HIP6304
The inductor, or load current, flows alternately from V
through Q1 and from ground through Q2. The HIP6304
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
average current per phase. Neglecting secondary effects,
the sampled current (I
current (I
I
Where: I
SAMPLE
FIGURE 8. TWO CHANNEL MULTIPHASE SYSTEM WITH
FIGURE 9. TWO CHANNEL MULTIPHASE SYSTEM WITH
25
20
15
10
5
0
25
20
15
10
5
0
LT
LT
= I
n = the number of channels
) by:
LT
CURRENT BALANCING DISABLED
CURRENT BALANCING ENABLED
= total load current
/ n + (V
IN
SAMPLE
V
CORE
) can be related to the load
- 3V
CORE
2
) / (6L x F
SW
, after Q1 is
SW
IN
x V
IN
)