Rainbow Electronics MAX1748 - Manual (Page 7)

MAX1748
Triple-Output TFT LCD DC-DC Converter
_______________________________________________________________________________________ 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
MAX1748toc16
1ms/div
R MAIN = 1k Ω, 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
MAX1748toc17
1ms/div
V MAIN = 10V, R MAIN = 50 Ω (200mA)
V SHDN
2V/div
0
0
V MAIN
5V/div
V NEG
5V/div
V
POS
10V/div
POWER-UP SEQUENCING
MAX1748toc18
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 125 Ω (typ).
2 FB
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.
4 IN
Supply Input. +2.7V to +5.5V input range. Bypass with a 0.1 µF 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 0.22 µF capacitor from this terminal to analog
ground (GND). External load capability to 50 µA.
7 FBP
Positive Charge-Pump Regulator Feedback Input. Regulates to 1.25V nominal. Connect feedback
resistive divider to analog ground (GND).
8 FBN Negative Charge-Pump Regulator Feedback Input. Regulates to 0V nominal.
9 SHDN Active-Low Logic-Level Shutdown Input. Connect SHDN to IN for normal operation.
10 DRVN Negative Charge-Pump Driver Output. Output high level is V SUPN , and low level is PGND.
11 SUPN Negative Charge-Pump Driver Supply Voltage. Bypass to PGND with a 0.1 µF capacitor.
12 DRVP Positive Charge-Pump Driver Output. Output high level is V SUPP , and low level is PGND.