MAX17499 데이터 시트보기 (PDF) - Maxim Integrated

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MAX17499

Current-Mode PWM Controllers with Programmable Switching Frequency

Maxim Integrated 

Current-Mode PWM Controllers with

Programmable Switching Frequency

Pin Description (continued)

PIN

NAME

FUNCTION

7

GND Ground Connection

8

NDRV External n-Channel MOSFET Gate Connection

9

VCC

Gate-Drive Supply. Internally generated supply from IN. Decouple VCC with a 10nF or larger capacitor

to GND.

IN Supply. Decouple with a 10nF or larger capacitor to GND. For bootstrapped operation (MAX17500),

10

IN connect a startup resistor from the input supply line to IN. Connect the bias winding supply to IN also (see

the Typical Application Circuit). For the MAX17499, connect IN directly to the 9.5V to 24V supply.

Detailed Description

The MAX17499/MAX17500 current-mode PWM con-

trollers are ideal for isolated and nonisolated power-

supply applications. The devices offer an accurate

input startup voltage programmable through the

UVLO/EN input. This feature prevents the power supply

from entering a brownout condition in case the input

voltage sags below its minimum value. This is important

since switching power supplies increases their input

supply current as the input voltage drops to keep the

output power constant. In addition to this externally

adjustable UVLO feature, the MAX17500 also offers a

bootstrap UVLO with a large hysteresis (11.9V) and

very low startup and operating current, which result in

an efficient universal input power supply. The switching

frequency of the devices is programmable with an

external resistor.

The MAX17500 is well suited for universal input (recti-

fied 85V AC to 265V AC) or telecom (-36V DC to

-72V DC) power supplies. The MAX17499 is well suited

for low-input-voltage (9.5V DC to 24V DC) power sup-

plies. The devices include an internal clamp at IN to

prevent the input voltage from exceeding the absolute

maximum rating (see Note 2 at the end of the Electrical

Characteristics table). The input is clamped when the

devices are started with a bleed resistor (R1 in Figure 1)

from a high input voltage and the UVLO/EN input is low.

The clamp can safely sink up to 2mA current.

VSUPPLY

R2

C5

R3

UVLO/EN 1

UFLG 2

FB 3

C2

COMP 4

R11 CS 5

MAX17500

10 IN

9 VCC

8 NDRV

7 GND

6 RT

D2

R1

T1

D1

VOUT

R13

Q1

C4

R14

C6

R15

R12

C2

C1

R4

0V

Figure 1. Nonisolated Power Supply with Programmable Input-Supply Start Voltage

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