ISL6551EVAL1 Intersil, ISL6551EVAL1 Datasheet - Page 38

• Manufacturer Part Number: ISL6551EVAL1
• Description: EVALUATION BOARD ISL6551
• Manufacturer: Intersil

Specifications of ISL6551EVAL1

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Isolated
• Voltage - Output: 3.3V
• Current - Output: 60A
• Voltage - Input: 36 ~ 75V
• Regulator Topology: Buck
• Frequency - Switching: 470kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6551
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

The measured loop and plant responses for 48V input and
3.3V output with the resistive load, which is characterized in
Figure 85, have a reasonable match with that of the
simplified model, as shown in Figure 87.
The loop response in overall “pure” resistive load conditions
was not tested. Instead, an electronic constant current load
was used. The results are not significantly off from that of the
“pure” resistive load within the frequencies of interest, as
shown in Figure 75. Figures 88 and Figure 89 show a good
prediction of phase margin and gain margin of the system
using the simplified model in overall operating conditions.
FIGURE 88. LOOP RESPONSE FOR 36V, 3.63V@6A AND 60A
FIGURE 87. LOOP RESPONSE FOR 38A “PURE”
-100
-100
-120
140
120
100
140
120
100
-20
-40
-60
-80
-20
-40
-60
-80
80
60
40
20
80
60
40
20
1.0E+02
1.0E+02
0
0
AREA OF INTEREST
RESISTIVE LOAD
1.0E+03
1.0E+03
Fequency (Hz)
Fequency (Hz )
1.0E+04
1.0E+04
38
1.0E+05
1.0E+05
1.0E+06
1.0E+06
Application Note 1002
Measured
Gain
Measured
Phase
Model
Gain
Model
Phase
M e as ure d
Gain (60A)
M e as ure d
Phas e (60A)
M e as ure d
Gain (6A)
M e as ure d
Phas e (6A)
M ode l Gain
(60A)
M ode l
Phas e (60A)
M ode l Gain
(6A)
M ode l
Phas e (6A)
Output Voltage
OUTPUT RIPPLE VOLTAGE
The output ripple voltage in different operating conditions is
no greater than 60mV, as summarized in Table 7. The results
show that the output has the largest output ripple voltage at
the highest input line and the highest output voltage since
the highest output ripple current is at this operating point.
Note that the ripple current in the table is not for
discontinuous mode. Figure 90 shows the converter
operating in burst mode at very light load. Figure 93 and 94
show the converter operates at 48V, 3.3V, and 0.5A load with
synchronous FETs turned off and on, respectively. The one
with synchronous FETs turned on has a larger duty cycle
than the one with synchronous FETs turned off, which runs
at discontinuous mode since the body diodes of the turned-
off FETs block the output inductor current from flowing
negatively. Note that the channel 1 represents the output
ripple voltage and the channel 3 represents the voltage
across the secondary winding.
FIGURE 89. LOOP RESPONSE FOR 75V, 2.64V@6A AND 60A
36V
48V
75V
75V
V
IN
-100
140
120
100
-20
-40
-60
-80
80
60
40
20
1.0E+02
0
3.63V
3.31V
2.64V
3.63V
V
OUT
TABLE 7. OUTPUT VOLTAGE RIPPLE
AREA OF INTEREST
1.0E+03
0.5A SYN
21.9mV
25.0mV
56.2mV
59.4mV
OFF
Fequency (Hz)
1.0E+04
0.5A SYN
25.0mV
28.1mV
37.5mV
46.9mV
ON
1.0E+05
34.4mV
48.4mV
59.4mV
32.8mv
LOAD
60A
1.0E+06
CURRENT
RIPPLE
10.8A
12.9A
5.4A
9.0A
Measured
Gain (60A)
Measured
Phase (60A)
Measured
Gain (6A)
Measured
Phase (6A)
Model Gain
(60A)
Model
Phase (60A)
Model Gain
(6A)
Model
Phase (6A)