at1738 Aimtron Technology, at1738 Datasheet - Page 14

• Manufacturer Part Number: at1738
• Description: Lcd Panel Step-up Converter With Analog Multi-function Outputs
• Manufacturer: Aimtron Technology

Positive Charge-Pump Regulator
Positive charge-pump regulator also contains internal P-channel and N-channel
MOSFETs to perform the power transfer. The internal MOSFETs switch at a constant
0.5* f
provides a regulated positive output voltage. During the first half-cycle, the N-channel
MOSFET turns on and flying capacitor C
During the second half-cycle, the N-channel MOSFET turns off, and the P-channel
MOSFET turns on, level shifting C
parallel with the reservoir capacitor C
output is controlled by the variable N-channel on-resistance.
Soft-Start
The step-up converter and positive charge-pump regulator uses an external capacitor
to perform the soft-start function. When VIN exceeds UVLO threshold, the internal
reference voltage of the step-up converter starts to rise. After reference voltage
reaches regulation, the step-up converter and positive charge-pump regulator start the
soft-start process. The soft-start capacitor is immediately charged at a constant current
of 4µA (typical). During this time, the SS voltage directly controls the peak inductor
current of the step-up converter and the feedback reference voltage of the positive
charge-pump regulator. The soft-start period is complete when V
When VIN falls below UVLO threshold, the soft-start capacitor is discharged to
ground.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone]
8/01/2008 REV: 0.8
OSC
Hz. The charge-pump inverts the doubles supply voltage (VMAIN) and
Figure 2. Charge-Pump Regulator Function Block
Fax: [phone]
T
SS
=
C
CPP
SS
POS
×
14
CPP
by VMAIN volts. This connects C
. The amount of charge transferred to the
. 1
. 4
24
µ 0
LCD Panel Step-up Converter with
charges to VMAIN minus a diode drop.
V
A
Preliminary Product Information
Analog Multi-Function Outputs
(sec)
Email:
WWW:
[e-mail]
http://www.aimtron.com.tw
SS
exceeds 1.24V.
AT1738
CPP
in