MAX1700EEE 查看數據表（PDF） - Maxim Integrated

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MAX1700EEE

1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters

Maxim Integrated 

1-Cell to 3-Cell, High-Power (1A),

Low-Noise, Step-Up DC-DC Converters

low-noise power for DSP, control, and RF circuitry.

Typically, RF phones spend most of their life in standby

mode with only short periods in transmit/receive mode.

During standby, maximize battery life by setting

CLK/SEL = 0; this places the IC in low-power mode (for

the lowest quiescent power consumption).

Designing a PC Board

High switching frequencies and large peak currents

make PC board layout an important part of design.

Poor design can cause excessive EMI and ground-

bounce, both of which can cause instability or regula-

tion errors by corrupting the voltage and current

feedback signals.

Power components (such as the inductor, converter IC,

filter capacitors, and output diode) should be placed as

close together as possible, and their traces should be

kept short, direct, and wide. A separate low-noise

ground plane containing the reference and signal

grounds should only connect to the power-ground

plane at one point. This minimizes the effect of power-

ground currents on the part. Consult the MAX1701 EV

kit manual for a layout example.

On multilayer boards, do not connect the ground pins

of the power components using vias through an internal

ground plane. Instead, place them close together and

route them in a star-ground configuration using compo-

nent-side copper. Then use vias to connect the star

ground to the internal ground plane.

Keep the voltage feedback network very close to the

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

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

feedback networks. Separate them with grounded

copper. Consult the MAX1700 evaluation kit for a full

PC board example.

Pin Configurations (continued)

Soft-Start

To implement soft-start, set CLK/SEL low on power-up;

this forces low-power operation and reduces the peak

switching current to 550mA max. Once the circuit is in

regulation and start-up transients have settled,

CLK/SEL can be set high for full-power operation.

Intermittent Supply/Battery Connections

When boosting an input supply connected with a

mechanical switch, or a battery connected with spring

contacts, input power may sometimes be intermittent

as a result of contact bounce. When operating in PFM

mode with input voltages greater than 2.5V, restarting

after such dropouts may initiate high current pulses that

interfere with the MAX1700/MAX1701 internal MOSFET

switch control. If contact or switch bounce is anticipat-

ed in the design, use one of the following solutions.

1) Connect a capacitor (CONB) from ONB to VIN, a 1MΩ

resistor (RONB) from ONB to GND, and tie ONA to GND

(Figure 12). This RC network differentiates fast input

edges at VIN and momentarily holds the IC off until VIN

settles. The appropriate value of CONB is 10-5 times the

total output filter capacitance (COUT), so a COUT of

200µF results in CONB = 2nF.

2) Use the system microcontroller to hold the

MAX1700/MAX1701 in shut down from the time when

power is applied (or reapplied) until the output capaci-

tance (COUT) has charged to at least the input voltage.

Power-on reset times of tens of milliseconds accom-

plish this.

3) Ensure that the IC operates, or at least powers up, in

PWM mode (CLK/SEL = high). Activate PFM mode only

after the VOUT has settled and all of the system’s power-

on reset flags are cleared.

TOP VIEW

LBP 1

LBN 2

REF 3

CLK/SEL 4

GND 5

POK 6

ONB 7

ONA 8

MAX1701

QSOP

16 LBO

15 POUT

14 OUT

13 LX

12 PGND

11 FB

10 AIN

9 AO

CONB

2nF

RONB

1M

7

ONB

13

LX

14

OUT

MAX1700

MAX1701

8 ONA

POUT 15

COUT

200µF

Figure 12. Connecting CONB and RONB when Switch or

Battery-Contact Bounce Is Anticipated

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