Rainbow-electronics MAX1779 Manual de usuario descargar pdf (Pagina 8)

MAX1779

Low-Power Triple-Output TFT LCD DC-DC

Converter

8 _______________________________________________________________________________________

Pin Description

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 1.25V nominal. Connect feedback resistive

divider to analog ground (GND).

3 INTG

Main Boost Integrator Output. If used, connect 2200pF 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).

8 FBN Negative Charge-Pump Regulator Feedback Input. Regulates to 0V nominal.

SHDN

Active-Low Logic-Level Shutdown Input. Connect SHDN to IN for normal operation.

Typical Operating Characteristics (continued)

(Circuit of Figure 5, V

= +3.3V, T

= +25°C, unless otherwise noted.)

4ms/div

POWER-UP SEQUENCING

MAX1779-23

A. V

SHDN

= 0 to 2V, 2V/div

B. V

MAIN

= 5V, R

MAIN

= 50Ω, 2.5V/div

C. V

NEG

= -8V, R

NEG

= 8kΩ, 10V/div

D. V

POS

= +12V, R

POS

= 12kΩ, 10V/div

10V

-10V

200µs/div

STARTUP WAVEFORM

(L = 33µH)

MAX1779-22

A. V

SHDN

= 0 to 2V, 2V/div

B. V

MAIN

= 5V, 1V/div

C. I

, 500mA/div

MAIN

= 50Ω

500mA

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 17 18

Converter 1

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Rainbow-electronics MAX1779 Manual de usuario Pagina 8

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