MAX1763 데이터 시트보기 (PDF) - Maxim Integrated

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MAX1763

1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter

Maxim Integrated 

1.5A, Low-Noise, 1MHz, Step-Up

DC-DC Converter

Bypass Components

A few ceramic bypass capacitors are required for prop-

er operation. Bypass REF to GND with 0.22µF. Also,

bypass OUT to GND with a 1µF ceramic capacitor, and

connect OUT to POUT with a 4.7Ω resistor. Each of

these components should be placed as close to their

respective IC pins as possible, within 0.2in (5mm).

Table 5 lists suggested suppliers.

Layout Considerations

High switching frequencies and large peak currents

make PC board layout a critical part of design. Poor

design will cause excessive EMI and ground bounce,

both of which can cause instability or regulation errors

by corrupting the voltage and current feedback signals.

Power components, such as the inductor, converter IC,

and filter capacitors, should be placed as close together

as possible, and their traces should be kept short, direct,

and wide. Keep the voltage feedback network very close

to the IC, within 0.2in (5mm) of the FB pins. Keep noisy

traces, such as those from the LX pin, away from the

voltage feedback networks and guarded from them

using grounded copper. If an external rectifier is used,

its traces must be kept especially short and use an

absolute minimum of copper area to avoid excess

capacitance that can slow the operation of the on-chip

synchronous rectifier and actually reduce efficiency.

Refer to the MAX1763 EV kit for a full PC board example.

The MAX1763 TSSOP-EP package features an

exposed thermal pad on its underside. This pad lowers

the package’s thermal resistance by providing a direct

thermal heat path from the die to the PC board.

Additionally, the ground pin (GND) also channels heat.

Connect the exposed thermal pad and GND to circuit

ground by using a large pad or multiple vias to the

ground plane.

Step-Up/Step-Down Applications

In some battery-powered applications, the battery volt-

age range overlaps the output voltage. In this case,

depending on the battery voltage, the regulator will

have to step the voltage up or down. To make a step-

up/step-down regulator, use the gain block to make a

linear regulator that follows the step-up converter. In

this case, if the battery voltage is low, then the circuit

will step up, and when the battery voltage is high, the

linear regulator will drop the voltage. See the Gain

Block section on how to use the gain block to make a

linear regulator. When the output voltage is greater than

the regulation voltage, then the synchronous rectifier

will be held on, reducing the dropout, and thus increas-

ing the efficiency when the battery voltage is close to,

but slightly above, the regulation voltage.

Chip Information

SUBSTRATE CONNECTED TO GND

14 ______________________________________________________________________________________

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