ISL6310EVAL1Z Intersil, ISL6310EVAL1Z Datasheet - Page 3

• 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: -

On-Board Load Transient Generator
Most bench-top electronic loads are not capable of
producing the current slew rates required to emulate most
modern loads. For this reason, a discrete transient load
generator is provided on the evaluation board, see Figure 2.
The generator produces a load pulse of 500μs in duration
with a period of 27ms. The pulse magnitude is approximately
25A with rise and fall slew rates of approximately 50A/μs as
configured. The short load current pulse and long duty cycle
is required to limit the power dissipation in the load resistors
(R38-R42) and MOSFETs (Q20, Q21). To engage the load
generator simply place switch S2, in the “OFF” position.
If the DAC code is changed from 11(1.500V), the transient
generator dynamics must be adjusted relative to the new
output voltage level. Place a scope probe in J10 to measure
the voltage across the load resistors and the dV/dt across
them as well. Adjust the load resistors, R38-R40, to achieve
the correct load current level. Change resistors R34-R37 to
increase or decrease the dV/dt as required to match the
desired dI/dt profile.
Inductor DCR Static Current Sense Points
A unique feature of the ISL6310EVAL1Z is the ability to
measure the voltage drop across the DCR of each channel’s
inductor by multimeter. This is accomplished with the use of
a capacitor and resistor series circuit which is placed in
parallel across each inductor as illustrated in Figure 3. When
VCC12
V
SUD50N03
OUT
46.4kΩ
OPEN
R38
R30
Q20
FIGURE 2. LOAD TRANSIENT GENERATOR
OPEN
R39
C55
1µF
SUD50N03
OPEN
R40
Q21
Q19
2N7002
U2
VSS
HS
402Ω
0.12Ω
R41
R33
HIP2100
3
BAV99LT1
BAV99LT1
S3
S4
R42
0.12Ω
HO
LO
C57
22µF
249Ω
562kΩ
249Ω
562Ω
R36
R35
R34
R37
J10
VLOAD
Application Note 1197
S2
ON
OFF
current, I
developed across the DCR will be sensed by the R-C circuit,
and an equivalent voltage will be developed across the
capacitor C.
In order to not affect the rest of the regulator, the time
constant of this R-C circuit is very large, so it can only be
used to measure static current, and not transient currents. To
calculate the current through each inductor measure the
voltage across the “DCR SENSE” points on the
ISL6310EVAL1Z and then divide that number by the DCR of
the inductor. This should give you an accurate reading of the
current through each channel during static loads.
Modifying the ISL6310EVAL1Z Design
Current Balance Resistors
The ISL6310 uses lower MOSFET r
to measure the current through each channel and balance
them accordingly. If the lower MOSFETs on the
ISL6310EVAL1Z are changed, the current balance resistors,
R18 and R20, should also be changed to adjust for the
change in r
sheet to choose new current sense resistors. R18 adjusts
the current in channel 1, R20 adjusts the currents in
channel 2, These resistors can also be changed to adjust for
any current imbalance due to layout, which is also explained
on page 19 of the ISL6310 data sheet.
Load Line (Droop) Regulation
The ISL6310 has an optional Droop function, the
ISL6310EVAL1Z board design is optimized for no Droop
case. For Droop option selection follow the following Table 3.
If Droop is implemented, the compensation network will
need to be recalculated for the Droop case for optimal loop
response and stability.
To create an output voltage change proportional to the total
current in all the active channels (droop), the ISL6310 uses
connected ICOMP)
connected IREF)
Disabled (Droop
Enabled (Droop
FIGURE 3. DCR STATIC CURRENT SENSE CIRCUIT
DROOP
ISL6310
L
TABLE 3. SELECTION OF DROOP OPTION
, flows through the inductor, the voltage drop
DS(ON)
. Refer to page 19 in the ISL6310 data
V
IN
OPEN
R46
0Ω
R
INDUCTOR
L
+ DCR SENSE -
I
L
DS(ON)
DCR
C
current sensing
C
December 12, 2006
OPEN
V
OUT
R45
0Ω
OUT
AN1197.1