ISL97650 Intersil Corporation, ISL97650 Datasheet - Page 16

• Manufacturer Part Number: ISL97650
• Description: 4-Channel Integrated LCD Supply
• Manufacturer: Intersil Corporation

The maximum V
R6 and R7 in the Typical Application Diagram determine
V
Improving Charge Pump Noise Immunity
Depending on PCB layout and environment, noise pick-up at
the FBP and FBN inputs, which may degrade load regulation
performance, can be reduced by the inclusion of capacitors
across the feedback resistors (e.g. in the Application
Diagram, C21 and C22 for the positive charge pump). Set
R6 • C20 = R7 • C19 with C19 ~ 100pF.
V
The V
switching the voltage on COM between ground, DRN and SRC,
under control of the start-up sequence and the CTL pin.
During the start-up sequence, COM is held at ground via an
NDMOS FET, with ~1k impedance. Once the start-up
sequence has completed, CTL is enabled and acts as a
multiplexer control such that if CTL is low, COM connects to
DRN through a 30Ω internal MOSFET, and if CTL is high,
COM connects to P
V
V
OFF_MAX
OFF
OFF
ON
Slice Circuit
ON
output voltage.
=
V
Slice Circuit functions as a three way multiplexer,
FBN
(
2x
)
FAULT
•
=
⎛
⎝
OFF
1
–
+
V
1.2MHz
OUT
R7
------- -
R6
SUP
output voltage of a single stage charge pump is:
A2
⎞
⎠
CLK
EN
–
internally via a 5Ω MOSFET.
+
V
V
REF
DIODE
16
0.4V
STOP
•
CONTROL
⎛
⎝
R7
------- -
R6
PWM
+
2 I
⎞
⎠
A1
FIGURE 17. NEGATIVE CHARGE PUMP BLOCK DIAGRAM
•
VDD
OUT
•
(
0.2V
R
ON
(
NOUT
(EQ. 21)
M2
M1
)H
ISL97650
VSUP
+
PGND
NOUT
FBN
R
ON
(
NOUT
820pF
The slew rate of start-up of the switch control circuit is mainly
restricted by the load capacitance at COM pin as following
equation:
Where V
P
between COM and DRN or P
MOSFET r
inserted, R
and C
In the Typical Application Circuit, R10, R11 and C15 give the
bias to DRN based on the following equation:
And R12 can be adjusted to adjust the slew rate.
(EQ. 20)
ΔV
------- -
V
Δt
OUT
DRN
C20
=
220nF
)L
C12
, which range is from 0V to 36V. R
------------------------------------ -
(
L
=
)
V
R
is the load capacitance of switch control circuit.
REF
i
g
V
-------------------------------------------------------------- -
||
ON
R
is the supply voltage applied to DRN or voltage at
DS(On)
L
V
L
g
R6
40k
is the load resistance of switch control circuit,
) C
⋅
×
R
R
11
10
L
, the trace resistance and the resistor
D3
+AVDD R
+
R
100pF
11
328k
C19
R7
D2
⋅
10
OUT
including the internal
C13
470nF
V
OFF
i
is the resistance
(-8V)
November 28, 2006
(EQ. 22)
(EQ. 23)
FN9198.3