Rainbow-electronics MAX1606 Manual de usuario descargar pdf (Pagina 7)

MAX1606

28V Internal Switch LCD Bias Supply

with True Shutdown

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Detailed Description

The MAX1606 step-up DC-DC converter operates from a

2.4V to 5.5V supply and converts voltages as low as

0.8V up to 28V. The device includes an internal switch-

ing MOSFET with a 0.8Ω on-resistance and selectable

current limit (Figure 1) and consumes 160µA of supply

current. During startup, the MAX1606 extends the mini-

mum off-time, limiting initial battery surge current. The

MAX1606 uses a P-channel MOSFET to isolate the out-

put from the input during true shutdown mode. This isola-

tion switch also includes short-circuit current limiting,

which protects the inductor and diode during a short-cir-

cuit fault.

Control Scheme

The MAX1606 features a minimum off-time, current-limit-

ed control scheme. The duty cycle is governed by a pair

of one-shots that set a minimum off-time and a maximum

on-time. The switching frequency can be up to 500kHz

and depends upon the load and input voltage. The peak

current limit of the internal N-channel MOSFET is pin

selectable and may be set at 125mA, 250mA, or 500mA

(Figure 2).

OFF

SHDN

= 0.8V TO 5.5V BATT

LIM

SHUTDOWN

LOGIC

1.25V

10µH

LOGIC

CONTROL

= 2.4V TO 5.5V

OUT

= V

TO 28V

OUT

MAX1606

CURRENT

LIMIT

ERROR

AMPLIFIER

LIM

Figure 1. Functional Diagram

Figure 2. Setting the Peak Inductor Current Limit

GND

LIM

GND

LIM

GND

LIM

NO CONNECTION

(2.4V TO 5.5V)

PEAK

= 500mA I

PEAK

= 250mA I

PEAK

= 125mA

MAX1606 MAX1606 MAX1606

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