ISL6551EVAL1 Intersil, ISL6551EVAL1 Datasheet - Page 16

• 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: -

differential amplifier, for remote sense purpose. Figure 17
shows the block diagram of the overall closed-loop system.
This peak current mode controlled system can be simplified
as shown in Figure 18, for setting up an initial feedback
compensation, and EQ. 55 defines the approximate open-
loop transfer function. The factor “2” in the equation is due to
that only half of the load is sensed by the current
transformer.
Designers should initially set a low cut-off frequency, such as
1kHz, system loop with this simplified model as a start point
and then continue to modify the loop under a stable
condition with a design tool such as a Venable System. Note
that the model does not include the slope compensation
component and does not account for subharmonic oscillation
phenomenon in current-mode controlled
converters. The high-frequency correction term given by
EQ. 56 will account for the phenomenon [4].
Hs S
Hopen S
Mc
Se
Wn
( )
=
=
=
=
( )
Sm
1
π Fsw
---------------------------------------------------- -
1
+
•
+
Se
-------
Sn
=
+
PWM
---------------------- -
Wn Qp
Sin
2N Ncs
------------------------ - Hd S
+
-
Rcs
S
•
•
RAMP
1
+
•
----------- -
Wn
S
Qp
2
Sn
ERROR AMPLIFIER
2
( ) He S
+
=
16
-
=
•
------------------------------------------------------------- -
π
Vs 2 D
------------------------- -
•
ISOLATION


2Lo
(
Mc
( ) Zo S
–
CURRENT TRANSFORMER
FIGURE 17. BLOCK DIAGRAM OF CLOSED-LOOP SYSTEM
•
•


)
REF.
1
1
•
–
( )
-------------------- -
N Ncs
D
--- -
2
Rcs
•


–
0.5
Application Note 1002
PRIMARY
DRIVERS
HIP2100s


(EQ. 55)
(EQ. 56)
DIFFERENTIAL AMPLIFIER
+
-
A better representation of the open loop transfer function for
the overall system is defined in EQ. 57:
Refer to Vatché’s Article [3] for another way of modeling the
loop.
Hopen2 S
V
IN
G=2N*Ncs/Rcs
ERROR AMP. [He(S)]
FIGURE 18. SIMPLIFIED CLOSED-LOOP MODEL
( )
-
PRIMARY SIDE
+
+
-
=
SECONDARY
POWER STAGE + OUTPUT FILTER
MIC4421s
DRIVERS
Hopen S
+
Vo
-
REF.
( ) Hs S
•
DIFFERENTIAL AMP. [Hd(S)]
( )
Zo(S)
SECONDARY SIDE
+
-
Lo
Lo
ESR
ESL
Co
Co
Ro
Ro
Vo
-
(EQ. 57)
+