MAX863EEE 查看數據表（PDF） - Maxim Integrated

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MAX863EEE

Dual, High-Efficiency, PFM, Step-Up DC-DC Controller

Maxim Integrated 

Dual, High-Efficiency, PFM, Step-Up

DC-DC Controller

Set Feedback Compensation

External voltage feedback to the MAX863 should be

compensated for stray capacitance and EMI in the

feedback network. Proper compensation is achieved

when the MAX863 switches evenly, rather than in wide-

ly spaced bursts of pulses with large output ripple.

Typically, lead compensation consisting of a 10pF to

220pF ceramic capacitor (C1 in Figure 7) across the

upper feedback resistor is adequate. Circuits with

VOUT or VDD greater than 7.5V may require a second

capacitor across the lower feedback resistor. Initially,

choose this capacitor so that R2C2 = R1C1. Set the

final values of the compensation capacitors based on

empirical analysis of a prototype.

PC Board Layout and Routing

High switching speeds and large peak currents make

PC board layout an important part of design. Poor lay-

out can cause excessive EMI and ground-bounce, both

of which can cause instability or regulation errors by

corrupting the voltage and current-feedback signals.

Place power components as close together as possi-

ble, and keep their traces short, direct, and wide. Keep

the extra copper on the board and integrate it into

ground as an additional plane. On multi-layer boards,

avoid interconnecting the ground pins of the power

components using vias through an internal ground

plane. Instead, place the ground pins of the power

components close together and route them in a “star”

ground configuration using component-side copper,

then connect the star ground to the internal ground

plane using multiple vias.

The current-sense resistor and voltage-feedback net-

works should be very close to the MAX863. Noisy

traces, such as from the EXT pins, should be kept away

from the voltage-feedback networks and isolated from

them using grounded copper. Consult the MAX863

evaluation kit manual for a full PC board example.

VIN = 1.8V TO VOUT1

VOUT1 = 5V

C1

220µF

10V

≤0.1Ω

R5

D1

MBRS340T3

L1

10µH

2A

C2

0.1µF

R7

100k

N1A

R1

50mΩ

C3

100µF

10V

≤0.1Ω

C4

100µF

10V

≤0.1Ω

L2

10µH

1A

D2

MBRS140

SENSE1 VDD BOOT

EXT1

EXT2

CS1

CS2

MAX863

R2

100mΩ

N1B

IRF7103

R3

909k

1%

LBO

FB2

LOW-BATTERY

DETECTOR OUTPUT

SHDN1

LBI

ON/OFF R4

SHDN2

49.9k

R6

REF

1%

C7

FB1 PGND GND

0.1µF

VOUT2 = 24V, 35mA

C5

22µF

35V

0.1Ω

C6

15pF

C8

270pF

Figure 8. Bootstrapped 3.3V Logic and 24V LCD Bias Supply

14 ______________________________________________________________________________________

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