ISL6310EVAL1Z Intersil, ISL6310EVAL1Z Datasheet - Page 19

• Manufacturer Part Number: ISL6310EVAL1Z
• Description: EVALUATION BOARD FOR ISL6310
• Manufacturer: Intersil

Specifications of ISL6310EVAL1Z

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.5V
• Current - Output: 60A
• Voltage - Input: 5 ~ 12V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6310
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

Current Balancing Component Selection
The ISL6310 senses the channel load current by sampling
the voltage across the lower MOSFET r
Figure 17. The ISEN pins are denoted ISEN1, and ISEN2.
The resistors connected between these pins and the
respective phase nodes determine the gains in the channel
current balance loop.
Select values for these resistors based on the room
temperature r
operating current, I
Equation 23.
PVCC
R
FIGURE 17. ISL6310 INTERNAL AND EXTERNAL CURRENT-
FIGURE 16. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
ISEN
FIGURE 15. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
PVCC
ISL6310
PHASE
=
R
-----------------------
50 10
R
r
DS ON
BOOT
LO2
HI2
R
R
⋅
LO1
HI1
SENSING CIRCUITRY
(
DS(ON)
–
6
)
⋅
FL
LGATE
I
------- -
ISEN(n)
FL
N
UGATE
of the lower MOSFETs; the full-load
; and the number of phases, N using
CHANNEL N
LOWER MOSFET
R
ISEN
19
R
G2
R
G
G1
G
V
R
C
IN
GI2
GD
R
C
C
GI1
GD
GS
CHANNEL N
UPPER MOSFET
+
C
DS(ON)
-
GS
I
L
x
S
r
S
DS ON
I
L
, as shown in
D
(
D
Q2
C
)
Q1
DS
C
(EQ. 23)
DS
ISL6310
In certain circumstances, it may be necessary to adjust the
value of one or more ISEN resistors. When the components of
one or more channels are inhibited from effectively dissipating
their heat so that the affected channels run hotter than
desired, choose new, smaller values of R
phases (see the section entitled “Channel Current Balance”
on page 10). Choose R
decrease in temperature rise in order to cause proportionally
less current to flow in the hotter phase.
In Equation 24, make sure that ΔT
rise above the ambient temperature, and ΔT
temperature rise above the ambient temperature. While a
single adjustment according to Equation 24 is usually
sufficient, it may occasionally be necessary to adjust R
two or more times to achieve optimal thermal balance
between all channels.
Load Line Regulation Component Selection (DCR
Current Sensing)
For accurate load line regulation, the ISL6310 senses the
total output current by detecting the voltage across the
output inductor DCR of each channel (As described in “Load
Line (Droop) Regulation” on page 12). As Figure 18
illustrates, an R-C network is required to accurately sense
the inductor DCR voltage and convert this information into a
“droop” voltage, which is proportional to the total output
current.
Choosing the components for this current sense network is a
two step process. First, R
chosen so that the time constant of this R
network matches the time constant of the inductor L/DCR.
Then the resistor R
sense network gain, obtaining the desired full load droop
voltage. Follow the steps below to choose the component
values for this R-C network.
R
1. Choose an arbitrary value for C
2. Plug the inductor L and DCR component values, and the
3. Use the new value for R
ISEN 2 ,
value is 0.01µF.
values for C
calculate the value for R
as well as the desired full load current, I
voltage, V
calculate the value for R
R
R
COMP
S
=
=
------------------------ - R
V
R
DROOP
=
ISEN
I
FL
DROOP
---------------------------------------
DCR C
COMP
⋅
ΔT
----------
ΔT
⋅
S
⋅
L
must be chosen to set the current
, and inductor DCR in Equation 26 to
COMP
2
1
COMP
chosen in Step 1, into Equation 25 to
ISEN,2
COMP
COMP
⋅
COMP
S
DCR
.
in proportion to the desired
and C
2
obtained from Equation 25,
COMP
.
is the desired temperature
COMP
ISEN
. The recommended
COMP
FL
1
is the measured
, full load droop
must be
for the affected
-C
August 7, 2008
COMP
(EQ. 24)
(EQ. 25)
(EQ. 26)
ISEN
FN9209.4