ISL6252 INTERSIL [Intersil Corporation], ISL6252 Datasheet - Page 21

• Manufacturer Part Number: ISL6252
• Description: Highly Integrated Battery Charger Controller for Notebook Computers
• Manufacturer: INTERSIL [Intersil Corporation]

The resistance R
inductor DCR, R
battery (normally between 50mΩ and 200mΩ). The worst
case for voltage mode control is when the battery is absent.
This results in the highest Q of the LC filter and the lowest
phase margin.
The compensation network consists of the voltage error
amplifier gm1 and the compensation network R
C
frequency pole and a zero at f
information is added to the feedback to create a second
zero, f
and ISL6252 add a pole at f
divider resistors that set the DC output voltage. For a 3-cell
battery, R
40, 41 and 42 relate the compensation network’s poles,
zeros and gain to the components in Figure 22. Figure 24
shows an asymptotic Bode plot of the DC/DC converter’s
gain vs frequency. It is strongly recommended that f
VCOMP
FIGURE 23. FREQUENCY RESPONSE OF THE LC OUTPUT
-100
-120
-140
-160
-10
-20
-30
-40
-50
-60
-20
-40
-60
-80
20
10
0
100 200
ZERO2
, which give the loop very high DC gain, a very low
R
3
BATTERY
= 320kΩ and R
. The low pass filter R
FILTER
500 1k
SENSE
O
R
= 200mΩ
BATTERY
is a combination of MOSFET r
and the internal resistance of the
2k
= 50mΩ
4
FREQUENCY
FILTER
= 64kΩ. Equations 37, 38, 39,
21
5k 10k 20k
ZERO1
F2
. R
, C
. Inductor current
3
F2
and R
between R
50k 100k 200k 500k
NO BATTERY
4
are internal
VCOMP
DS(ON)
ZERO1
ISL6252, ISL6252A
SENSE
,
,
is
approximately 30% of f
of f
COMPENSATION BREAK FREQUENCY EQUATIONS
f
f
f
f
f
f
ZERO1
ZERO2
LC
FILTER
POLE1
ESR
FIGURE 24. ASYMPTOTIC BODE PLOT OF THE VOLTAGE
LC
=
-20
-40
-60
.
40
20
=
0
-------------------------------
(
2π L C
0.1k
------------------------------------------- -
(
=
=
=
=
2π C
--------------------------------------------------- -
(
⎛
⎜
⎝
---------------------------------------------------------------------- -
(
------------------------------------------ -
(
2π R
1
2π C
------------------------------------------------------- -
2π R
2π R
⋅
⋅
CONTROL LOOP GAIN
⋅
⋅
o
⋅
⋅
1
o
⋅
)
R
SENSE
f
SENSE
R
VCOMP
F2
ZERO1
1
VCOMP
ESR
1
COMPENSATOR
MODULATOR
LOOP
⋅
1k
C
1
F2
)
LC
⋅
⋅
⋅
C
)
FREQUENCY (Hz)
C
R
and f
o
OUT
1COMP
)
⎞
⎟
⎠
ZERO2
10k
⋅
f
ZERO2
⎛
⎜
⎝
)
-------------------- -
R
4
R
+
4
f
is approximately 70%
R
LC
F
3
ESR
⎞
⎟
⎠
⋅
100k
⎛
⎝
gm1
----------- -
f
POLE1
5
⎞
⎠
August 25, 2010
f
FILTER
(EQ. 37)
(EQ. 38)
(EQ. 39)
(EQ. 40)
(EQ. 41)
(EQ. 42)
FN6498.3
1M