MAX8717 Просмотр технического описания (PDF) - Maxim Integrated

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MAX8717

Interleaved High-Efficiency, Dual Power-Supply Controllers for Notebook Computers

Maxim Integrated 

Interleaved High-Efficiency, Dual Power-Supply

Controllers for Notebook Computers

PIN

MAX8716

MAX8717/

MAX8757

1

1

2

2

3

3

4

4

—

5

5

6

6

7

—

8

7

9

8

10

9

11

10

12

11

13

12

14

13

15

Pin Description

NAME

FUNCTION

VCC

SKIP1

REF

SKIP2

FSEL

ON1

ON2

ILIM2

PGOOD2

FB2

CSL2

CSH2

BST2

DH2

LX2

Analog Supply Input. Connect to the system supply voltage (+4.5V to +5.5V) through a

series 20Ω resistor. Bypass VCC to AGND with a 1µF or greater ceramic capacitor.

Low-Noise Mode Control for SMPS1. Connect SKIP1 to GND for normal idle-mode

(pulse-skipping) operation or to VCC for PWM mode (fixed frequency). Connect to REF

for low-noise mode.

2.0V Reference Voltage Output. Bypass REF to AGND with a 0.1µF or greater ceramic

capacitor. The reference can source up to 50µA. Loading REF degrades output voltage

accuracy according to the REF load-regulation error (see the Typical Operating

Characteristics). The reference shuts down when both ON1 and ON2 are low.

Low-Noise Mode Control for SMPS2. Connect SKIP2 to GND for normal idle-mode

(pulse-skipping) operation or to VCC for PWM mode (fixed frequency). Connect to REF

for low-noise mode.

Frequency Select Input. This four-level logic input sets the controller’s switching

frequency. Connect FSEL to VCC for 500kHz, to REF for 300kHz, and to GND for 200kHz

operation.

SMPS1 Enable Input. Drive ON1 high to enable SMPS1. Drive ON1 low to shut down

SMPS1.

SMPS2 Enable Input. Drive ON2 high to enable SMPS2. Drive ON2 low to shut down

SMPS2.

SMPS2 Peak Current-Limit Threshold Adjustment. Connect ILIM2 to VCC to enable the

default 50mV current-limit threshold. In adjustable mode, the current-limit threshold

across CSH2 and CSL2 is precisely 1/10th the voltage seen at ILIM2 over a 500mV to

2.0V range. The logic threshold for switchover to the 50mV default value is

approximately VCC - 1V.

SMPS2 Open-Drain Power-Good Output. PGOOD2 is low when SMPS2 is more than

10% below its regulation threshold, during soft-start, and in shutdown.

Feedback Input for SMPS2. Connect FB2 to VCC for fixed 5V output. In adjustable mode,

FB2 regulates to 1V.

Negative Current-Sense Input for SMPS2. Connect to the negative terminal of the

current-sense element. Figure 8 describes two different current-sensing options.

Positive Current-Sense Input for SMPS2. Connect to the positive terminal of the current-

sense element. Figure 8 describes two different current-sensing options.

Boost Flying Capacitor Connection for SMPS2. Connect to an external capacitor and

diode as shown in Figure 1. An optional resistor in series with BST2 allows the DH2 turn-

on current to be adjusted.

High-Side Gate-Driver Output for SMPS2. DH2 swings from LX2 to BST2.

Inductor Connection for SMPS2. Connect LX2 to the switched side of the inductor. LX2

is the lower supply rail for the DH2 high-side gate driver.

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