ISL6562EVAL1 Intersil, ISL6562EVAL1 Datasheet - Page 10

• Manufacturer Part Number: ISL6562EVAL1
• Description: EVALUATION BOARD ISL6562
• Manufacturer: Intersil

Specifications of ISL6562EVAL1

• Main Purpose: Special Purpose DC/DC, VRM Supply
• Outputs And Type: 1, Non-Isolated
• Power - Output: 60W
• Voltage - Output: 1.5V
• Current - Output: 40A
• Voltage - Input: 5V, 12V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6562
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

A. Specifications:
B. Calculate R
C. Determine Frequency Setting Capacitor CT:
D. Select Inductor Ripple Current (∆I
E. Determine the Inductors:
F. Output Capacitors:
The ISL6560 data sheet describes in more detail the following equations. There are several changes from the computations in
the body of the data sheet. First, an operating frequency of 400kHz was chosen. Next, this design sequence shows the method of
setting the initial no load voltage at the DAC setting and offsetting the no load voltage 15mV above the programmed DAC voltage.
FIGURE A. OSCILLATOR FREQUENCY vs. TIMING CAPACITOR
R OUT
∆I L
Output Current:
Input Voltage:
Output Voltage: VDAC + 15mV
Output Voltage for Calculations:
V
Droop Voltage: 65mV
Oscillator Frequency: 400kHz (f
3000
1000
From curve above, for 400kHz use 120pF.
Choose 40% of IOUT
Or 8A / Channel
L
Capacitor ESR R OUT
DAC
100
=
Six capacitors < 1.66mΩ
Total Capacitance = 9mF
=
Sonya 1500µF, 4V OS-CON Capacitors
have an ESR < 10mΩ
=
0
=
V IN V OUT
--------------------------------- -
40A 0.4
= 1.8V + 15mV
956nH
f SW
----------- -
V DROOP
--------------------------- -
2
50
OUT
I OUT
–
×
×
100 150 200 250 300
∆I L
:
=
≅
12V
40A
16A
×
=
CAPACITOR CT (pF)
V OUT
-----------------
65mV
--------------- -
V IN
40A
10
=
=
=
1.63mΩ
SW
-----------------------------------
200kHz 8A
1.63mΩ
12V 1.8V
)
L
350 400
):
–
ISL6560 Supply Design Sequence
×
ISL6560/62 Evaluation Board
×
450 500
1.8V
------------
12V
.
G. Input Capacitor’s RMS Current:
H. Current Sense Resistor (R
I. R
J. R
K. V
VSET
For 40A with a duty cycle (D) of:
SENSE
L
R L
SET
R SENSE
Pensioned 470µF, 16V Rubdown ZA series capacitors
have a RMS current rating of 1.6A.
Six capacitors were selected.
∴
Where: I
I RMS
V
V
Power
Selection:
I RMS
am Amplifier Gain
OUT
Use the curve of Figure B
Power
SET
=
=
D
Computation for No Load Voltage = DAC:
0.3
0.2
0.1
ni = ∆V
=
------------------------------------------
gm R OUT 2
, the no load voltage programed to the DAC voltage
=
0
The multiplier from Figure B is 0.24.
ni R SENSE
, the voltage set at the COMP pin
1V
FIGURE B. CURRENT MULTIPLIER vs. DUTY CYCL
Dissipation:
0
=
=
1V
=
1V
=
P
=
×
×
V OUT
-----------------
I PEAK D
+
0.24
=
= 20A + 4A = 24A
24A
V IN
=
432mW
+
+
COMP
I RIPPLE R SENSE ni
--------------------------------------------------------------------- -
Use a 5mΩ resistor
I P
8A 5mΩ 12.5
---------------------------------------------
----------------------------------------------- -
I OUT
-------------- -
250mV
2
2
×
V CS TH
2
0.1
×
×
×
40A
=
0.15
D
/ V
×
=
1.8V
------------
+
(
12V
×
CS
2
I RIPPLE
------------------------ -
×
=
DUTY CYCLE (V
=
gm RL
R SENSE
=
×
)MIN
×
(from data sheet)
2
1.25V
9.6A
0.2
5mΩ
------------------------------------------------------- -
2.2mS 1.63mΩ 2
=
2
×
Used a 1W resistor
0.15
SENSE
12.5 5mΩ
(Using half 0f ripple current
=
=
×
2.2mS 8.7k
0.3
O
×
×
------------------------ -
20A
/ V
142mV
):
IN
)
+
×
8A
0.4
×
=
=
=
5.07mΩ
8.7kΩ
19.1
0.5
E