Rainbow-electronics MAX5974D Manual de usuario descargar pdf

_______________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX5974A/MAX5974B/MAX5974C/MAX5974D

Active-Clamped, Spread-Spectrum,

Current-Mode PWM Controllers

19-5331; Rev 1; 9/10

Ordering Information

General Description

The MAX5974_ provide control for wide-input-voltage,

active-clamped, current-mode PWM, forward converters

in Power-over-Ethernet (PoE) powered device (PD) appli-

cations. The MAX5974A/MAX5974C are well-suited for

universal or telecom input range, while the MAX5974B/

MAX5974D also accommodate low input voltage down

to 10.5V.

The devices include several features to enhance supply

efficiency. The AUX driver recycles magnetizing cur-

rent instead of wasting it in a dissipative clamp circuit.

Programmable dead time between the AUX and main

driver allows for zero-voltage switching (ZVS). Under light-

load conditions, the devices reduce the switching fre-

quency (frequency foldback) to reduce switching losses.

The MAX5974A/MAX5974B feature unique circuitry to

achieve output regulation without using an optocoupler,

while the MAX5974C/MAX5974D utilize the traditional

optocoupler feedback method. An internal error amplifier

with a 1% reference is very useful in nonisolated design,

eliminating the need for an external shunt regulator.

The devices feature a unique feed-forward maximum

duty-cycle clamp that makes the maximum clamp volt-

age during transient conditions independent of the line

voltage, allowing the use of a power MOSFET with lower

breakdown voltage. The programmable frequency dither-

ing feature provides low-EMI, spread-spectrum operation.

The MAX5974_ are available in 16-pin TQFN-EP pack-

ages and are rated for operation over the -40°C to +85°C

temperature range.

Features

S Peak Current-Mode Control, Active-Clamped

Forward PWM Controller

Regulation Without Optocoupler (MAX5974A/

MAX5974B)

Internal 1% Error Amplifier

100kHz to 600kHz Programmable Q8% Switching

Frequency, Synchronization Up to 1.2MHz

Programmable Frequency Dithering for Low-EMI,

Spread-Spectrum Operation

Programmable Dead Time, PWM Soft-Start,

Current Slope Compensation

Programmable Feed-Forward Maximum Duty-

Cycle Clamp, 80% Maximum Limit

Frequency Foldback for High-Efficiency Light-

Load Operation

Internal Bootstrap UVLO with Large Hysteresis

100µA (typ) Startup Supply Current

Fast Cycle-by-Cycle Peak Current-Limit, 35ns

Typical Propagation Delay

115ns Current-Sense Internal Leading-Edge

Blanking

Output Short-Circuit Protection with Hiccup Mode

Reverse Current Limit to Prevent Transformer

Saturation Due to Reverse Current

3mm x 3mm, Lead-Free, 16-Pin TQFN-EP

Applications

PoE IEEE

802.3af/at Powered Devices

High-Power PD (Beyond the 802.3af/at Standard)

Active-Clamped Forward DC-DC Converters

IP Phones

Wireless Access Nodes

Security Cameras

Note: All devices are specified over the -40°C to +85°C operating temperature range.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc.

PART TOP MARK PIN-PACKAGE UVLO THRESHOLD (V) FEEDBACK MODE

MAX5974AETE+ +AHY 16 TQFN-EP* 20 Sample/Hold

MAX5974BETE+ +AHZ 16 TQFN-EP* 10 Sample/Hold

MAX5974CETE+ +AIA 16 TQFN-EP* 20 Continuously Connected

MAX5974DETE+ +AIB 16 TQFN-EP* 10 Continuously Connected

1 2 3 4 5 6 ... 25 26

Indice de contenidos

Pagina 1 - Current-Mode PWM Controllers

_______________________________________________________________ Maxim Integrated Products 1For pricing, delivery, and ordering information, pleas

Pagina 2

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers10 Typical

Pagina 3

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers11

Pagina 4

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers12

Pagina 5

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers13

Pagina 6

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers14

Pagina 7

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers15 Detailed DescriptionThe MAX59

Pagina 8

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers16Bootstrap Undervoltage LockoutThe devices have an i

Pagina 9

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers17Figure 3. Dead Time Between AUXDRV and NDRVstartup

Pagina 10

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers18Oscillator/Switching FrequencyThe ICs’ switching fr

Pagina 11

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers19Frequency Foldback for High-Efficiency Light-Load O

Pagina 12

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers2Stresses beyond those listed under “Absolute Maximu

Pagina 13

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers20Typically, fTRI should be set close to 1kHz. The re

Pagina 14

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers21Active Clamp CircuitTraditional clamp circuits prev

Pagina 15

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers22During on-time, the coupled output is:S CCOUPLED-ON

Pagina 16

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers23

Pagina 17

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers24 Ty

Pagina 18

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers25 Ty

Pagina 19

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

Pagina 20

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers3ELECTRICAL CHARACTERISTICS (continued)(VIN = 12V (fo

Pagina 21

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers4ELECTRICAL CHARACTERISTICS (continued)(VIN = 12V (fo

Pagina 22

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers5ELECTRICAL CHARACTERISTICS (continued)(VIN = 12V (fo

Pagina 23 - MAX5974D

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers6

Pagina 24 - MAX5974B

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers7 Typical

Pagina 25 - PROCESS: BiCMOS

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers8 Typical

Pagina 26

MAX5974A/MAX5974B/MAX5974C/MAX5974DActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers9 Typical

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