Datasheet

MAX1748/MAX8726
Triple-Output TFT-LCD
DC-DC Converters
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(Circuit of Figure 5, V
IN
= 3.3V, T
A
= +25°C, unless otherwise noted.)
Pin Description
V
MAIN
5V/div
2V
10V
0
I
LX
500mA/div
MAIN BOOST STARTUP WAVEFORM
MAX1748/8726 toc16
1ms/div
R
MAIN
= 1kΩ, V
MAIN
= 10V
V
SHDN
2V/div
0
0
V
MAIN
5V/div
2V
10V
0
I
LX
500mA/div
MAIN BOOST STARTUP
WAVEFORM WITH LOAD
MAX1748/8726 toc17
1ms/div
V
MAIN
= 10V, R
MAIN
= 50Ω (200mA)
V
SHDN
2V/div
0
0
V
MAIN
5V/div
V
NEG
5V/div
V
POS
10V/div
MAX1748 POWER-UP SEQUENCING
MAX1748/8726 toc18
2ms/div
V
MAIN
= 10V, V
NEG
= -5V, V
POS
= 15V
V
SHDN
2V/div
PIN NAME FUNCTION
1 RDY Active-Low, Open-Drain Output. Indicates all outputs are ready. The on-resistance is 125Ω (typ).
2FB
Main Boost Regulator Feedback Input. Regulates to 1.248V nominal. Connect feedback resistive
divider to analog ground (GND).
3 INTG
Main Boost Integrator Output. If used, connect 470pF to analog ground (GND). To disable integrator,
connect to REF.
4IN
Supply Input. +2.7V to +5.5V input range. Bypass with a 0.1µF capacitor between IN and GND, as
close to the pins as possible.
5 GND Analog Ground. Connect to power ground (PGND) underneath the IC.
6 REF
Internal Reference Bypass Terminal. Connect a 0.22µF capacitor from this terminal to analog ground
(GND). External load capability to 50µA.
7 FBP
Positive Charge-Pump Regulator Feedback Input. Regulates to 1.25V nominal. Connect feedback
resistive divider to analog ground (GND).
V
MAIN
5V/div
V
NEG
5V/div
V
POS
10V/div
MAX8726 POWER-UP SEQUENCING
MAX1748/8726 toc19
4ms/div
V
MAIN
= 10V, V
NEG
= -5V, V
POS
= 15V
V
SHDN
5V/div