at1731a Aimtron Technology, at1731a Datasheet - Page 13

• Manufacturer Part Number: at1731a
• Description: Dc-dc Power Ic For Tft Panel
• Manufacturer: Aimtron Technology

forces the current through the inductor to ramp back down , transferring the energy stored in
the magnetic field to the output capacitor and load. To add higher flexibility to the selection
of external component values, the device uses external loop compensation.
Negative Charge-Pump Regulator
Negative charge-pump contains internal P-channel and N-channel MOSFETs to perform the
power transfer. The internal MOSFETs switch at a constant 600kHz (0.5x f
charge-pump inverts the supply voltage (VDDN) and provides a regulated negative output
voltage. Figure 3 shows charge-pump block diagram. During the first half-cycle, the
P-channel MOSFET turns on and flying capacitor C
During the second half-cycle, the P-channel MOSFET turns off, and the N-channel MOSFET
turns on, level shifting C
If the voltage across C
flows from C
output is controlled by the variable N-channel on-resistance.
Positive Charge-Pump Regulator
Positive charge-pump also contains internal P-channel and N-channel MOSFETs to perform
the power transfer. The internal MOSFETs switch at a constant 600kHz (0.5x f
charge-pump inverts the doubles supply voltage (VDDP) and provides a regulated positive
output voltage. During the first half-cycle, the N-channel MOSFET turns on and flying
capacitor C
N-channel MOSFET turns off, and the P-channel MOSFET turns on, level shifting C
V
across C
(V
transferred to the output is controlled by the variable N-channel on-resistance.
DDP
CPP
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone]
2/8/2006 REV:1.1
V
Vmain
NEG
+V
volts. This connects C
C
NEG
DDP
POS
Cout
V
V
CPP
), charge flows from C
V
NEG
REF
plus a diode drop is lower than the level shifted flying capacitor voltage
REF
CPN
= -(R10/R11)x
=1.23V
charges to V
to C
R10
C
1.23V
R11
CPN
NEG
NEG
V
REF
CPN
FBN
V
SWN
until the diode turns off. The amount of charge transferred to the
DDN
minus a diode drop is lower than the voltage across C
Fax: [phone]
. This connects C
CPP
DDP
in series with the reservoir capacitor C
minus a diode drop. During the second half-cycle, the
CPP
Driver
to C
POS
Switch
Block
CPN
until the diode turns off. The amount of charge
13
in parallel with the reservoir capacitor C
Driver
CPN
1.23V
DC-DC Power IC for TFT Panel
Preliminary Product Information
charges to V
WWW:
Email:
V
FBP
SWP
DDP
http://www.aimtron.com.tw
[e-mail]
DDN
R4
R3
C
minus a diode drop.
CPP
Cout
POS
. If the voltage
AT1731A
V
V
POS
REF
C
=(1+R3/R4)x
CPN
=1.23V
POS
VDDP
OSC
OSC
V
, charge
POS
). The
). The
CPP
NEG
V
REF
by
.