Intersil ISL6560, Application Note

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ISL6560/62 Evaluation Board
L. gm Amplifier Output Load Network:
M. V
SET
Computation for No Load Voltage = DAC +15mV:
N. gm Amplifier Output Load Network:
O. C
C
and R
C
Selection:
R
U
R
B
V
REF = 3V
this voltage is V
SET
R
B
V
SET
V
REF
V
SET
–
---------------------------------------- = R
U
×
R
U
3V
1.25V
---------------- = 8.7k
×
20.9k =
To COMP pin,
R
U
V
REF
V
SET
----------------- = R
L
×
R
B
1.25V
3V 1.25V
–
----------------------------- = 20.9k
×
14.9k =
R
U
R
B
||
R
L
=
V
OUT
, no load voltage to be set 15mV above
Added output voltage of the gm amplifier will be:
15mV X gm Amplifier gain = 15mv x 19.1 = 287mV
1V
8A 5m
Ω
12.5
× ×
2
--------------------------------------------- + = 287mV +
V
SET
1V
I
RIPPLE
R
SENSE
ni
× ×
2
---------------------------------------------------------------------- 287mV + + =
1V 250mV + = 287mV
+
1.536V =
programed DAC voltage
R
B
V
SET
V
REF
V
SET
–
---------------------------------------- = R
U
×
R
U
3V
1.54V
---------------- = 8.7k
×
16.9K =
R
B
1.54V
3V 1.54V
–
----------------------------- = 16.9k
×
17.8k =
R
U
R
B
V
REF = 3V
this voltage is V
SET
To COMP pin,
R
U
V
REF
V
SET
----------------- = R
L
×
R
U
R
B
||
R
L
=
C
C
R
OUT
C
OUT
×
R
L
------------------------------------------
1.63m
Ω
9mF
×
8.7k
----------------------------------------- 1.68nF = = =
R
U
R
B
||
R
L
=
R
C
= 0.5 x R
L
= 0.5 x 8.7k = 4.35k
R
L
C
C
R
C
AC Equivalent
COMP pin
R
U
R
B
V
REF = 3V
C
C
R
C
To COMP pin