isl97652 Intersil Corporation, isl97652 Datasheet - Page 16

• Manufacturer Part Number: isl97652
• Description: 4-channel Integrated Lcd Supply With Dual Vcom Amplifiers
• Manufacturer: Intersil Corporation

In voltage doubler configuration, the maximum V
For Voltage Tripler using additional external diodes and capacitors (Figure 18B):
V
Negative Charge Pump Design Consideration
The negative charge pump consists of an internal switcher
M1, M2 which drives external steering diodes Dx and Dx via
a pump capacitor (CN) to generate the negative V
supply. An internal comparator (A1) senses the feedback
voltage on FBN and turns on M1 for a period up to half a
CLK period to maintain V
0.5V. External feedback resistor R5 is referenced to V
V
V
V
ON
ON_MAX(2x)
ON
ON_MAX(3x)
output voltage is determined by the following equation:
=
V
FBP
=
×
=
FAULT
3 V
⎛
⎝
2
1
•
•
+
(
SUP
R7
------- -
R8
V
F
OSC
SUP
⎞
⎠
A2
–
CLK
EN
(FBN)
4 V
–
•
V
DIODE
16
DIODE
1.14V
STOP
in regulated operation at
CONTROL
PWM
FIGURE 18A. V
)
DRVP
–
–
A1
2 I
2 I
VDC
•
•
OUT
OUT
0.1µF
C
•
•
P
1.265V
(
(
C
0.1µF
R
R
ON
P’
FIGURE 18B. VOLTAGE TRIPLER
ON
ONH
ONH
OFF
V
SUP
is as given by the following equation:
FUNCTION DIAGRAM (VOLTAGE DOUBLER)
REF
+
+
D6
R
R
ONL
ONL
.
ISL97652
M2
M1
D7
FIGURE 18.
V
)
SUP
DRVP
)
GND
FBP
C
1µF
(EQ. 15)
(EQ. 16)
(EQ. 17)
ON
D6’
2.2nF
C5
0.1µF
C
P
D7’
R8
10k
V
C
1µF
SUP
ON’
V
ON
D6
(30V)
100pF
232k
C4
R7
D7
C
1µF
ON
V
ON
(30V)
November 2, 2007
FN9287.1